A method and device for estimating sediment in a river basin and a storage medium

Abstract

The application provides a catchment sediment estimation method, which comprises the following steps: collecting various types of basic data of a target catchment, arranging the basic data into a grid form and performing unified spatial registration, dividing the various types of basic data based on the small catchment boundary as the spatial unit of sediment estimation; for each small catchment, calculating the gravity erosion, debris flow erosion, gully erosion and slope erosion respectively to obtain the time and space distribution of various types of erosion and total erosion in the target catchment; for the above four types of erosion, calculating the sediment yield and deposition of the small catchment scale respectively; based on the calculated sediment yield, calculating the suspended sediment transport capacity of the small catchment in the main river system according to the upstream and downstream relationship of the small catchment in the target catchment, and combining the dredging, reservoir sedimentation and the input and output of the suspended sediment in the river section to obtain the distribution of the suspended sediment transport capacity along the flow direction of the main river system. The application can comprehensively quantify the time and space distribution of the sediment in the erosion of the catchment, the sediment yield of the catchment and the sediment transport of the river.

Description

TECHNICAL FIELD

[0001] The present application belongs to the fields of watershed environment governance, soil and water conservation, mountain disaster and environment, remote sensing information technology, and particularly relates to a watershed sediment estimation method and device and storage medium. BACKGROUND

[0002] Watershed erosion is a geomorphic process of displacement of surface materials under the action of external forces. The materials produced by watershed erosion enter the river system and become sediment, which is transported to the downstream or deposited in the river channel. Watershed erosion and sediment transport are key physical processes of watershed surface evolution and landform shaping, and also have a profound impact on human economic and social activities in the watershed. Although erosion, sediment transport, sediment deposition and output from the watershed are continuous physical processes, the current research on watershed erosion and sediment production and sediment transport is generally fragmented. For example, watershed erosion is generally a research topic in the field of soil and water conservation, mainly focusing on the erosion process on the slope surface, while sediment transport is generally the focus of the field of water conservancy engineering and river geomorphology, and the correlation between slope erosion and sediment supply to the river channel is weak. However, with the intensification of climate change and human activities, water-sediment coupling disasters are becoming more and more common, and the demand for understanding the temporal and spatial distribution of erosion and sediment at the watershed scale is increasingly strong. For example, extreme watershed flood disaster events are often related to extreme rainfall runoff, mountain torrent debris flow outbreak, flood evolution and other processes in the upper reaches, so prevention and control cannot be limited to the middle and lower reaches of towns, but needs to be put on the whole watershed scale. For another example, watershed erosion and sediment transport have a great impact on the construction and operation of water conservancy and hydropower projects in the watershed, especially the reservoir sedimentation, so understanding the temporal and spatial distribution of erosion and sediment transport in the watershed can effectively promote the development of sediment source determination, targeted soil and water conservation measure design and implementation, etc.

[0003] Sediment budget is a method to study the erosion, sediment transport, sediment deposition and sediment distribution in a basin. It can combine the slope erosion process and the river sediment transport process, break through the subject division of traditional soil and water conservation and water conservancy engineering, and quickly reveal the spatial and temporal distribution pattern of basin erosion and sediment transport, thereby providing strong scientific support for soil and water conservation, river evolution, disaster prevention and mitigation, and sustainable development at the basin scale. However, the existing sediment budget method has the following problems: first, the erosion mainly considers slope erosion, and pays less attention to gravity erosion (disaster process dominated by gravity unloading such as collapse and landslide), debris flow erosion and gully erosion process which are common in the edge area of Qinghai-Tibet Plateau and concentrate sediment production, and lacks quantitative description or depends on field observation to a large extent, which is difficult and costly; second, the sediment production calculation is mainly based on sediment transport ratio (the ratio of sediment transport at the outlet of the basin to the total erosion of the basin), but the sediment transport ratio is mainly based on empirical value, which is obviously local and lacks a widely applicable quantitative calculation method. In view of the foregoing actual needs of basin sediment budget and the problems existing in the existing method, a basin sediment budget method needs to be specially developed. SUMMARY

[0004] The purpose of the present application is to propose a basin sediment budget method which can comprehensively quantify the spatial and temporal distribution of sediment in the erosion of the basin, the sediment production of the basin and the sediment transport of the river in multiple physical processes, aiming at the deficiencies and shortcomings of the existing basin sediment budget method. The method comprehensively considers and quantifies different types of erosion, and provides sediment transport ratio calculation methods for each type of erosion, and finally quantifies the sediment transport process in the river, which can provide technical support for the comprehensive management of the basin, and has important popularization and application prospect.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The first aspect of the present application provides a basin sediment budget method, comprising:

[0007] Step S1, collecting the basic data of the target basin, including rainfall, soil, vegetation, terrain, orthographic image and hydrological data, arranging various types of basic data into grid form and performing unified spatial registration, setting the small watershed boundary as the spatial unit of sediment budget, dividing various types of basic data based on the small watershed boundary, and dividing the time period of various types of basic data at the small watershed scale based on the time scale requirement of sediment budget;

[0008] Step S2, for each small watershed, calculating the erosion amount according to different erosion types, i.e. gravity erosion, debris flow erosion, gully erosion and slope erosion, to obtain the spatial and temporal distribution of various types of erosion amount and total erosion amount in the target basin;

[0009] Step S3: For gravity erosion, calculate the sediment yield based on the amount of material input into the river from the landslides connected to the water system, and subtract the sediment yield from the gravity erosion amount to obtain the sedimentation amount of gravity erosion at the small watershed scale.

[0010] For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is first calculated separately. Then, the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. Specifically, the sediment transport ratio at the small watershed scale for debris flow erosion is calculated based on the bulk density, flow rate, and inflow angle of the debris flow and the main river. The sediment transport ratio at the small watershed scale for gully erosion and slope erosion is calculated based on the sediment connectivity index at the grid scale within each small watershed.

[0011] The spatiotemporal distribution of sediment yield and sedimentation in the target watershed is obtained based on the sediment yield and sedimentation of various types of erosion at the small watershed scale.

[0012] Step S4: Based on the sediment yield of all sub-basins in the target basin calculated in Step S3, calculate the suspended sediment transport of the sub-basins in the main river system segment by segment according to the upstream and downstream relationship of the confluence rivers of each sub-basin in the target basin. Combine the sand dredging, reservoir siltation, and the input and output of suspended sediment in the river section to obtain the distribution of suspended sediment transport along the flow direction of the main river system.

[0013] In some embodiments, the basic data collected in step S1 includes rainfall data with a temporal resolution of not less than 3 hours, soil data including the organic matter content in sand, silt, and clay of the topsoil, vegetation data including the normalized difference vegetation index and vegetation type, topographic data using a digital elevation model with a spatial resolution of not less than 30 m, and hydrological data including river system data, flow, runoff, and sediment transport information within the target watershed. The basic data also includes land use types for calculating dimensionless soil and water conservation measures factors. The spatial resolution used for unified spatial registration of basic data for various grid types is consistent with the spatial resolution of the digital elevation model.

[0014] The sub-basin is the basin corresponding to the smallest order of rivers in Horton's Law. Based on the digital elevation model, the target basin is divided into I sub-basins B1, B2, ... B1. i ,…B I The area, topographic elevation difference, average slope, channel length, channel width, and channel slope of each small watershed were statistically analyzed.

[0015] In some embodiments, in step S2,

[0016] To address gravity erosion, T is identified through multi-period orthophotos of the watershed. j The newly added landslide area during the period, based on the landslide area statistics T j Small watershed B in a certain time periodi The total volume of material released by the collapse and landslide within the area, as T j Small watershed B in a certain time period i Gravitational erosion (E) G ) ij T j The time unit is determined based on the estimated sediment demand, and the duration ΔT is the same for each time period;

[0017] To address debris flow erosion, the first step is to obtain data from small watershed B based on rainfall data. i During time period T j Information on all valid rainfall events within the timeframe, including the duration and average intensity of each event, is used to determine whether each event triggers a debris flow based on a rainfall threshold trigger condition. If an event is determined not to trigger a debris flow, its outflow volume is set to 0; if it is determined to trigger a debris flow, its outflow volume is calculated. The T-value is then statistically analyzed. j Small watershed B in a certain time period i The total volume of debris ejected by the mudslide is taken as T. j Small watershed B in a certain time period i Debris flow erosion (E D ) ij ;

[0018] To address gully erosion, T j Small watershed B in a certain time period i The gully is divided into several gully segments. The gully erosion rate of each segment is calculated, and T is calculated based on the gully erosion rate. j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij ;

[0019] To address slope erosion, the T value for each grid cell was calculated by modifying the general soil loss equation RUSLE. j The soil erosion modulus within a given time period is multiplied by the grid area to obtain the grid scale T. j Soil erosion over a period of time; small watershed B i T is obtained by summing the soil erosion of each grid within the range. j Small watershed B in a certain time period i Slope erosion (E) S ) ij ;

[0020] The summation of the four types of erosion measurements yields T. j Small watershed B within the time period i Total erosion (E) ij .

[0021] In some embodiments, T is calculated according to the following formula. j Small watershed B in a certain time period i Gravitational erosion (E) G ) ij :

[0022]

[0023] In the formula, ρ G The density of the collapsed and landslide material; (V) G ) k For T j Small watershed B in a certain time period i The mass of material released by the k-th landslide, where K is T. j Small watershed B in a certain time period i Total number of internal collapses and landslides; volume V of material released for a single collapse or landslide. G Calculate according to the following formula:

[0024]

[0025] In the formula, A G The area of ​​a single landslide is denoted by α and γ, where α is 0.05 ± 0.02, γ is 1.1 to 1.3 for soil landslides, and γ is 1.3 to 1.6 for rock landslides.

[0026] The small watershed B i During time period T j All valid rainfall events within the area can be obtained using the following steps:

[0027] First, the rainfall data after spatial division is used to calculate the rainfall in each time period t of the small watershed according to the following formula. τ Average rainfall within:

[0028]

[0029] In the formula, For small watershed B i During time period t τ Average rainfall within, t τ M represents the temporal resolution of the rainfall data, and M represents the watershed B. i The total number of grid cells within, For small watershed B i The m-th grid cell in the time period t τ The amount of rainfall;

[0030] Small watershed B i During time period t τ average rainfall Divide by the time period t τ As a small watershed B i During time period tτ The average rainfall intensity;

[0031] Iterate through each time period T j We obtained the time series matrix of rainfall intensity for each small watershed, and then determined the intensity of each small watershed in each time period T in chronological order. j The rainfall intensity is used to determine the start of a valid rainfall event. A valid rainfall event begins when the rainfall intensity exceeds a first preset value, and ends when the rainfall intensity falls below the first preset value but continues for at least a second preset value. A valid rainfall event is defined as the period during which the rainfall intensity continuously exceeds the first preset value. The duration D and average rainfall intensity of each valid rainfall event are recorded. Thus, obtain small watershed B i During time period T j Information on all valid rainfall events within the region;

[0032] The method of determining whether each effective rainfall event triggers a debris flow based on rainfall threshold triggering conditions is as follows:

[0033] Let the rainfall threshold be I c The following formula is used to calculate the results on a small watershed basis:

[0034] I c =α D D -β

[0035] In the formula, α D Both β and β are constants;

[0036] When the average rainfall intensity of an effective rainfall event At that time, it was considered that no mudslide would be triggered;

[0037] When the average rainfall intensity of an effective rainfall event At that time, it was considered that a debris flow was triggered, and the statistics of small watershed B were compiled. i In T j Rainfall data for each event that could trigger mudslides during the specified period. Where l represents the rainfall event number that will trigger a mudslide, with a total of L events, D l and Small watershed B i In T j The duration and average rainfall intensity of the l-th rainfall event that will trigger debris flows within the time period are determined, and the volume of debris ejecta V of each debris flow is calculated using the following formula. D :

[0038]

[0039] In the formula, Q D γ is the peak flow rate of the debris flow; DThe density of debris flow; γ W The density of pure water; γ S Q is the bulk density of solid materials in a debris flow. P For torrential rain and flood flow; K P F is the confluence coefficient; i For small watershed B i D. C The congestion coefficient is represented by T, the duration of a mudslide, and L. D U represents the length of the main debris flow channel; D S represents the velocity of the debris flow; S represents the slope of the gully bed.

[0040] The T j Small watershed B in a certain time period i Debris flow erosion (E D ) ij Calculate according to the following formula:

[0041]

[0042] In the formula, ρ D Density of debris ejected by mudslide; (V) D ) l For T j Small watershed B in a certain time period i The volume of ejecta from the first debris flow in the inner zone;

[0043] The T j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij Calculate according to the following formula:

[0044] (E g ) ij =(G g ) ij ·ΔT

[0045]

[0046] In the formula, L s r is the length of the s-th segment of the channel; s Let be the average annual erosion rate of the slope of the gully section, and be the average annual rate of change of the cross section of the gully section; ρ is the density of eroded sediment; ΔT is the temperature of T. j Duration of the period;

[0047] The T j Small watershed B within the time period i Slope erosion (E) S ) ij Calculate according to the following formula:

[0048]

[0049] In the formula, A g A represents the area of ​​a single grid cell. m For small watershed B i The soil erosion modulus of the m-th grid within the range; M is the watershed B. i The total number of grid cells within.

[0050] In some embodiments, in step S3

[0051] Regarding sediment production and deposition from gravity erosion, if the landslide location is not connected to a river system, the sediment production and deposition from gravity erosion caused by the landslide are both zero. If the landslide location is connected to a river system, then the T... j Small watershed B in a certain time period i Deposition amount due to internal gravity erosion (D) G ) ij Calculate according to the following formula:

[0052] (D G ) ij =(E G ) ij -T' G

[0053]

[0054] T G =k G ·ρ·w G ·L G ·h

[0055] h = cQ f

[0056] In the formula, (E G ) ij For T j Small watershed B in a certain time period i The amount of gravitational erosion; p and P are respectively T j Small watershed B in a certain time period i Numbering and total number of landslides and collapses connected to the river system within the area; T G The mass of material input into a river from a single landslide; w G L represents the average distance a single landslide extends from the riverbank into the water, obtained based on historical remote sensing imagery or field surveys. G k represents the length of the river segment affected by a single landslide. G ρ is the correction factor; h is the density of eroded sediment; ρ is the density of L. G The average water depth of the corresponding river section; Q is the flow rate of the main river at a single landslide location; c and f are both coefficients; T G ′ for T jSmall watershed B in a certain time period i The amount of sediment yield corresponding to the amount of gravity erosion;

[0057] To determine the sediment production and deposition from debris flow erosion, T is first calculated using the following formula. j Small watershed B in a certain time period i Sediment transport ratio (SDR) of internal debris flow erosion D ) ij :

[0058]

[0059] In the formula, θ is T j Small watershed B in a certain time period i The angle at which the main ditch flows into the main river; γ m and γ D T respectively j Small watershed B in a certain time period i The bulk density of the main river and debris flows; q m and q D T respectively j Small watershed B in a certain time period i The unit width discharge of the main river and the debris flow are given. The unit width discharge of the main river is obtained from hydrological data, and the unit width discharge of the debris flow is calculated as q. D =Q D / w D w D For T j Small watershed B in a certain time period i The width of the debris flow channel, Q D For T j Small watershed B in a certain time period i Peak flow rate of debris flow;

[0060] Then based on the sediment transport ratio (SDR) D ) ij Calculate T j Small watershed B in a certain time period i Debris flow erosion results in sediment yield and deposition:

[0061] (T D ) ij =(E D ) ij ·(SDR D ) ij

[0062] (D D ) ij =(E D ) ij -(T D ) ij

[0063] In the formula, (T) D) ij For T j Small watershed B in a certain time period i The amount of sediment produced by debris flow erosion, (D D ) ij For T j Small watershed B in a certain time period i The amount of sediment eroded by debris flows;

[0064] To address sediment production and deposition in gully and slope erosion, T is first calculated based on the sediment connectivity index at the grid scale within each small watershed. j Small watershed B in a certain time period i Sediment transport ratio (SDR) of gully erosion or slope erosion IC ) ij :

[0065]

[0066] In the formula, (SDR) max ) ij It is T j Small watershed B in a certain time period i The theoretically achievable maximum sediment transport ratio is related to the topsoil texture; IC ij For T j Small watershed B in a certain time period i The average sediment connectivity index is taken as T. j Small watershed B in a certain time period i The mean of the sediment connectivity index at each grid scale; IC0 and k are correction coefficients for calculating the sediment transport ratio;

[0067] Then based on the sediment transport ratio (SDR) IC ) ij Calculate T j Small watershed B in a certain time period i The sediment yield and deposition corresponding to gully erosion, and the sediment yield and deposition corresponding to slope erosion:

[0068] (T g ) ij =(E g ) ij ·(SDR IC ) ij

[0069] (D g ) ij =(E g ) ij -(T D ) ij

[0070] (T S ) ij =(ES ) ij ·(SDR IC ) ij

[0071] (D S ) ij =(E S ) ij -(T S ) ij

[0072] In the formula, (E g ) ij For T j Small watershed B in a certain time period i The amount of gully erosion, (T g ) ij and (D) g ) ij T respectively j Small watershed B in a certain time period i The corresponding sediment yield and deposition amount for gully erosion; (E S ) ij For T j Small watershed B in a certain time period i The amount of slope erosion, (T) S ) ij and (D) S ) ij T respectively j Small watershed B in a certain time period i The amount of sand production and deposition corresponding to the amount of slope erosion.

[0073] In some embodiments, the sediment connectivity index at the grid scale within a small watershed is denoted as IC, and is calculated according to the following formula:

[0074]

[0075] IS m =RI m +C·P

[0076]

[0077] In the formula, D up The upslope component of a small watershed reflects the upstream sediment yield potential; The average impedance factor of the upslope catchment area of ​​a small watershed represents the resistance of surface roughness to water and sediment flow. A represents the average slope of the uphill catchment area of ​​a small watershed. up D represents the area of ​​the upslope catchment area of ​​a small watershed; dn d represents the downslope component of a small watershed, reflecting the path resistance of sediment reaching its destination; mW represents the length of the flow path along the steepest downhill direction for the m-th grid cell within a small watershed; m Let SS be the impedance factor of the m-th grid within a certain small watershed; m IS represents the slope gradient of the m-th grid cell within a small watershed; max IS represents the maximum surface index of the small watershed where the raster is located. m RI is the surface index of the m-th grid cell within a small watershed. m Let f be the roughness index of the m-th grid cell within a certain small watershed; To calculate RI m Used A raster moving scan pane, x m x represents the elevation of a certain grid cell. s For the area around a certain grille The average elevation of each grid cell; C is the dimensionless vegetation cover factor; P is the dimensionless soil and water conservation measure factor.

[0078] In some embodiments, step S4 specifically includes:

[0079] Based on the distribution of slope, river width, and river type along the course, the rivers in the target basin are divided into X river segments R1, R2, ... R... x ,…R X The regulations stipulate that at most one reservoir or lake shall be provided in each section of the river, and that the reservoir or lake shall be located at the inlet of the river section.

[0080] Calculate the suspended sediment transport in the target basin for each river segment, for T j Any section R within the time period x Its output suspended sediment load (SS) out ) xj for:

[0081]

[0082] In the formula, (SS) in ) xj For T j River section R during the period x The amount of suspended sediment input into the main river from upstream; (I) T ) n River section R x The amount of suspended sediment input into the main river from the nth tributary, where n and N are the river section R, respectively. x The internal tributary numbers and total number are then... T represents j River section R during the time period x The amount of suspended sediment input into the main river from all tributaries within the river section R xThe amount of suspended sediment IT from a tributary entering the main river is calculated based on the small watershed sediment yield obtained in step S3; (E B ) xj For T j River section R during the time period x The particle size in the riverbank erosion is consistent with the mass of suspended sediment, calculated based on the work done by the water flow; (O F ) xj For T j River section R during the time period x The amount of suspended sediment deposited on the floodplain, based on T j River section R during the time period x The average discharge, average settling velocity of suspended sediment, and average area of ​​the floodplain were calculated. (O) D ) xj For T j River section R during the time period x The amount of suspended sediment transported away in irrigation or water diversion projects, based on T j River section R during the time period x The average output flow rate and average sediment content of the output water flow are calculated in irrigation or water diversion projects; (O R ) xj For T j River section R during the time period x The amount of suspended sediment deposited in reservoirs or lakes is obtained based on hydrological sediment observation data, or based on T... j River section R during the period x Suspended sediment load (SS) input into the main river from upstream in ) xj It is calculated based on the average sediment retention rate of reservoirs or lakes.

[0083] In some embodiments, the amount of suspended sediment I input from a tributary into the main river within a single river segment is calculated according to the following formula. T :

[0084] I T =T G ′·(Δ s ) G +T D ·(Δ s ) D +T g ·(Δ s ) g +T S

[0085] In the formula, T G ′ for T j Small watershed B in a certain time period i The amount of sediment yield corresponding to the amount of gravity erosion; T DT represents the sediment yield corresponding to the debris flow erosion volume of a specific tributary within a single river section, in a specific watershed. g T represents the sediment yield corresponding to the erosion of a specific tributary within a single river section in a small watershed; S This refers to the sediment yield corresponding to the slope erosion of a specific tributary within a single river section, specifically for a small watershed; (Δ) s ) G 、(Δ s ) D 、(Δ s ) g T respectively G ′、T D and T g The proportion of suspended sediment was obtained by extracting the characteristic particle size proportion of suspended sediment in the target watershed from the gradation curves of landslide deposits, debris flow fan deposits, and gully slope materials.

[0086] T is calculated according to the following formula. j River section R during the time period x The particle size of the riverbank erosion is consistent with the mass of suspended sediment (E). B ) xj :

[0087] (E B ) xj =b(ρ w g(Q B ) xj S xj (h) B ) xj (L B ) xj (ρ B ) xj ((Δ s ) B )x j

[0088] In the formula, b is the adjustment parameter; the variable with the subscript x represents the river segment R. x Average value, where the subscript j represents the time period number; ρ w Where is the density of pure water; g is the acceleration due to gravity; Q B S is the discharge at the river's flat beach; S is the river's slope; h B L represents the height of the riverbank. B ρ is the length of the river segment; B The density of the material on the shoreline; (Δ s ) B The proportion of suspended sediment in the material along the riverbank;

[0089] T is calculated according to the following formula. j River section R during the time period x The amount of suspended sediment deposited on the floodplain (OF ) xj :

[0090]

[0091] In the formula, (O f ) xj For T j River section R during the time period x The average discharge of the inland river flowing through the floodplain, i.e., T j In all floods during a given period where the peak flow in the river segment exceeded the average flow at the floodplain, the peak flow exceeded the average of the average flow. xj For T j River section R during the time period x Average settling velocity of suspended sediment; (A) f ) xj For T j River section R during the time period x The average area of ​​the floodplain within the area;

[0092] T is calculated according to the following formula. j River section R during the time period x The amount of suspended sediment transported away in irrigation or water diversion projects (O D ) xj :

[0093] (O D ) xj =(Q D ) xj ·ΔT·(C D ) xj

[0094] In the formula, (Q D ) xj For T j River section R during the time period x The average output flow rate in irrigation or water diversion projects, (C D ) xj For T j River section R during the time period x The average sediment content of the output water flow in irrigation or water diversion projects;

[0095] For situations where there is no hydrological and sediment monitoring data at the inlet or outlet of a reservoir or lake, T is calculated using the following formula. j River section R during the time period x Suspended sediment deposition in reservoirs or lakes (O R ) xj :

[0096] (Q R ) xj =(SS) in ) xj ·TExj

[0097]

[0098] In the formula, TE xj For T j River section R during the time period x The average sediment retention rate of reservoirs or lakes; C R The effective storage capacity of a reservoir or lake; I R This refers to the average annual runoff of a reservoir or lake.

[0099] A second aspect of the present invention provides a watershed sediment estimation device, comprising:

[0100] The basic data acquisition module is configured to collect basic data of the target watershed, including rainfall, soil, vegetation, topography and hydrological data, organize various basic data into grid form and perform unified spatial registration, set the small watershed boundary as the spatial unit for sediment estimation, spatially divide various basic data based on the small watershed boundary, and divide various basic data at the small watershed scale into time periods based on the time scale requirements of sediment estimation.

[0101] The erosion calculation module is configured to calculate erosion for each small watershed according to different erosion types, namely gravity erosion, debris flow erosion, gully erosion, and slope erosion, and obtain the spatiotemporal distribution of various types of erosion and total erosion within the target watershed.

[0102] The sediment yield and deposition calculation module is configured to calculate the sediment yield and deposition corresponding to various erosion amounts at the small watershed scale. Specifically, for gravity erosion, the sediment yield is calculated based on the amount of material input into the river from landslides connected to the water system, and the deposition amount of gravity erosion at the small watershed scale is obtained by subtracting the sediment yield from the gravity erosion amount. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is calculated first, and then the sediment yield and deposition amount at the small watershed scale are calculated based on various sediment transport ratios. For debris flow erosion, the sediment transport ratio at the small watershed scale is calculated based on the bulk density, flow rate, and inflow angle of debris flow and the main river. For gully erosion and slope erosion, the sediment transport ratio at the small watershed scale is calculated based on the sediment connectivity index at the grid scale within each small watershed. Based on the sediment yield and deposition amounts of various erosions at the small watershed scale, the spatiotemporal distribution of sediment yield and deposition amounts in the target watershed is obtained.

[0103] The suspended sediment transport calculation module is configured to calculate the suspended sediment transport in the main river system segment by segment based on the sediment yield of all sub-basins in the target watershed at each time period. It calculates the suspended sediment transport in the sub-basins in the main river system segment by segment according to the upstream and downstream relationship of the confluence rivers of each sub-basin in the target watershed. It also combines the sand dredging, reservoir siltation, and the input and output of suspended sediment in the river section to obtain the distribution of suspended sediment transport along the flow direction of the main river system.

[0104] A third aspect of the present invention provides a computer-readable storage medium storing computer instructions for causing the computer to execute the watershed sediment estimation method according to any embodiment of the first aspect of the present invention.

[0105] The beneficial effects of this invention are as follows:

[0106] 1. The method of this invention comprehensively considers and quantifies the contribution of various erosion types to watershed erosion, especially quantifying two important but often overlooked erosion types: gravity erosion and debris flow erosion. This makes it more in line with the actual situation when applied in areas where landslides and debris flows are frequent.

[0107] 2. By linking erosion-sediment production-deposition physical processes at the small watershed scale and linking sediment production-main river transport physical processes at the river system scale, a quantitative description of the number of erosion, sediment production and transport processes in the entire target watershed can be achieved, and the spatiotemporal distribution within the target watershed can be given, thereby enabling rapid and accurate location of the main erosion areas and sediment source areas within the watershed.

[0108] 3. The methodology mainly relies on satellite imagery and hydrological data, has low requirements for on-site measurement and sampling, is easy to control in terms of cost, and allows for rapid modeling and easy promotion. Attached Figure Description

[0109] Figure 1 This is an overall flowchart of a watershed sediment estimation method provided in the first aspect embodiment of the present invention;

[0110] Figure 2 This is a schematic diagram of small watershed erosion and sediment transport according to the first aspect of the present invention;

[0111] Figure 3 This is a schematic diagram of the process of calculating suspended sediment transport in a river section in a watershed sediment estimation method provided in the first aspect of the present invention;

[0112] Figure 4 This is a schematic diagram of the structure of an electronic device provided in a third aspect embodiment of the present invention. Detailed Implementation

[0113] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0114] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0115] See Figure 1 , Figure 2 The first aspect of the present invention provides a method for watershed sediment estimation, comprising the following steps:

[0116] Step S1: Collect basic data of the target watershed, including rainfall, soil, vegetation, topography and hydrological data. Organize the various basic data into grid form and perform unified spatial registration. Set the small watershed boundary as the spatial unit for sediment estimation. Based on the small watershed boundary, spatially divide the various basic data. Based on the time scale requirements of sediment estimation, divide the various basic data at the small watershed scale into time periods.

[0117] Step S2: For each small watershed, calculate the erosion amount according to different erosion types, namely gravity erosion, debris flow erosion, gully erosion, and slope erosion, to obtain the spatiotemporal distribution of various types of erosion amount and total erosion amount in the target watershed.

[0118] Step S3: For gravity erosion, calculate the sediment yield based on the amount of material input into the river from the landslides connected to the water system, and subtract the sediment yield from the gravity erosion amount to obtain the sedimentation amount of gravity erosion at the small watershed scale.

[0119] For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is first calculated separately. Then, the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. Specifically, the sediment transport ratio at the small watershed scale for debris flow erosion is calculated based on the bulk density, flow rate, and inflow angle of the debris flow and the main river. The sediment transport ratio at the small watershed scale for gully erosion and slope erosion is calculated separately based on the sediment connectivity index at the grid scale within their respective small watersheds.

[0120] The spatiotemporal distribution of sediment yield and sedimentation in the target watershed is obtained based on the sediment yield and sedimentation of various types of erosion at the small watershed scale.

[0121] Step S4: Based on the sediment yield of all sub-basins in the target basin calculated in Step S3, calculate the suspended sediment transport of the sub-basins in the main river system segment by segment according to the upstream and downstream relationship of the confluence rivers of each sub-basin in the target basin. Combine the sand dredging, reservoir siltation, and the input and output of suspended sediment in the river section to obtain the distribution of suspended sediment transport along the flow direction of the main river system.

[0122] In some embodiments, step S1 involves collecting and preprocessing basic data of the target watershed, specifically including:

[0123] Step S11: Basic data collection.

[0124] Basic data, including rainfall, soil, vegetation, topography, and orthophotos, were collected for the target watershed. Rainfall data was collected as raster data with a temporal resolution of 3 hours or higher; soil data, primarily consisting of organic matter content in topsoil sand, silt, and clay, was collected as raster data; vegetation data, including the Normalized Difference Vegetation Index (NDVI) and vegetation types (trees, shrubs, etc.), was collected as raster data; topographic data used a digital elevation model (DEM) with a spatial resolution of at least 30 meters; additionally, land use types were included as basic data for calculating dimensionless soil and water conservation factors. All basic data underwent unified spatial registration, and the spatial resolution was standardized to match the DEM spatial resolution. Multiple orthophotos of the target area were required, with consistent spatial resolution and unified spatial registration across all images.

[0125] Collect hydrological data for the target watershed, including river system data (which can be extracted from a DEM or pre-extracted river system data from the target watershed), and flow, runoff, and sediment transport information from hydrological stations, with a time resolution preferably down to the daily scale. If there are no hydrological stations in the target watershed, find the nearest downstream hydrological station with water and sediment data; if there is existing hydrological data such as flow, depth, or data obtained from distributed hydrological model simulations in the target area, also collect it.

[0126] Step S12: Basic data preprocessing.

[0127] Spatial scale division: The watershed corresponding to the smallest order of rivers in Horton's Law is defined as a small watershed, which is used as the spatial unit for sediment estimation. Based on the DEM, the target watershed is divided into I small watersheds B1, B2, ... B i ,…B I The area, topographic elevation difference, average slope, channel length, channel width and channel slope of each small watershed were statistically analyzed.

[0128] Time scale division: Determine the time scale of the final output data (e.g., one year, two years) based on the sediment estimation requirements, and uniformly divide the basic data with time series characteristics of the target watershed collected in step S11 into J time periods T1, T2, ... T according to this time scale. j ,…,T J The duration of each time period is ΔT.

[0129] Rainfall data preprocessing: First, GIS-based analysis tools are used to obtain data for each small watershed (B). iA vector data file of the range was used to establish a mapping relationship between small watersheds and raster-format rainfall data. The spatial weighted average method was then used to calculate the small watershed B. i In each time period t τ The average rainfall within the area is calculated as follows:

[0130]

[0131] In the formula, For small watershed B i During time period t τ Average rainfall, t τ The temporal resolution of rainfall data is typically 1 hour or 3 hours, where M represents the watershed B. i The total number of grid cells in A g For the area of ​​a single grid cell, For small watershed B i The m-th grid cell in the time period t τ The amount of rainfall.

[0132] Small watershed B i During time period t τ Average rainfall divided by t τ This represents the average rainfall intensity in that small watershed during that time period. Iterate through each time period T. j We obtained the time series matrix of rainfall intensity for each small watershed, and then determined the rainfall intensity of each small watershed in each time period T in chronological order. j The rainfall intensity is used to determine the start of an effective rainfall event. A rainfall intensity greater than 1 mm / h is considered the start of an effective rainfall event, while a rainfall intensity less than 1 mm / h that continues for at least 6 hours is considered the end of an effective rainfall event. A period of continuous rainfall intensity greater than 1 mm / h is considered an effective rainfall event, and its duration D (in hours) and average rainfall intensity are recorded. (Unit: mm / h) and other indicators to obtain the small watershed B i During time period T j Information on all valid rainfall events within the region.

[0133] In some embodiments, step S2 involves calculating the erosion amount at the small watershed scale according to different erosion types, and then calculating T. j Watershed erosion over a given period is categorized into four types: gravity erosion, debris flow erosion, gully erosion, and slope erosion. (See [link to relevant documentation]). Figure 2 The calculation process for various types of erosion is described below:

[0134] Step S21, Gravity Erosion Amount

[0135] Gravity erosion is mainly caused by landslides and collapses within the watershed. Te is identified using visual recognition or deep neural network methods based on multiple periods of orthophotos of the watershed. jThe newly added landslide area within the time period is calculated, and then the volume of material released by the landslides during that time period is estimated based on the relationship between the landslide area and volume. For a single landslide, the volume of material released is calculated as follows:

[0136]

[0137] In the formula, V G A represents the volume of material released by a single landslide. G The area of ​​a single landslide is α, and γ are coefficients. α is generally taken as 0.05±0.02. For soil landslides, γ is taken as 1.1 to 1.3, and for rock landslides, γ is taken as 1.3 to 1.6.

[0138] Statistical T j Small watershed B in a certain time period i The total volume of material released by the collapse and landslide within the area is taken as the gravitational erosion amount (E). G ) ij :

[0139]

[0140] In the formula, ρ G The density of the landslide material is typically taken as 2.0–2.5 t / m³ for rock landslides. 3 For soil landslides, the typical value is 1.6–2.3 t / m. 3 K is T j Small watershed B in a certain time period i Total number of collapses and landslides; k is T j Small watershed B in a certain time period i The numbering of internal collapse and landslide material, (V) G ) k For T j Small watershed B in a certain time period i The amount of material released by the kth collapse and landslide.

[0141] Step S22, Debris Flow Erosion Amount

[0142] Debris flows strongly transport sediment within a small watershed, causing channel erosion and carrying large amounts of material to the alluvial fan at the gully mouth. Calculating the volume of ejecta from the debris flow is used to approximate the erosion volume of the small watershed. Since debris flow gullies are often narrow and deep, it is difficult to directly determine their occurrence using remote sensing imagery, and on-site investigation is too time-consuming. Considering that most debris flows are triggered by rainfall, a rainfall threshold is used to determine whether a debris flow has occurred. Let the rainfall threshold be I. c Based on equation (4), the calculation is performed on a small watershed basis:

[0143] I c =α D D -β (4)

[0144] In the formula, D represents the duration (h) of an effective rainfall event occurring within a small watershed, and α D Since β is a constant, for the Wenchuan earthquake zone, α can be taken as... D =66.36, β=-0.79.

[0145] Based on the set rainfall threshold I c Determine T j Small watershed B in a certain time period i Did each effective rainfall event trigger a mudslide?

[0146] like If no mudslide is triggered, the volume of the ejected material is considered to be 0.

[0147] like Then it is considered that a debris flow was triggered, and the small watershed B is statistically analyzed. i In T j Rainfall data for each event that could trigger mudslides within the specified time period Where l represents the rainfall event number that could trigger debris flows, with a total of L events and D l and Small watershed B i In T j The duration and average rainfall intensity of the first rainfall event that could trigger a debris flow within the time period were determined, and the volume of debris ejected from the debris flow, V, was calculated using equations (5) to (9). D :

[0148]

[0149] In the formula, Q D Peak flow rate of debris flow (unit: m³) 3 / s); The coefficient 19 / 72 in equation (5) is an empirical coefficient given by the "Design Code for Debris Flow Investigation and Prevention in Hydropower Projects" (NB / T 10139-2019); γ D The density of debris flow is determined through field surveys or regional debris flow characteristics; γ W For the density of clear water, except under extreme conditions of extremely high sediment transport, the density of the main river is unlikely to change significantly compared to clear water. Therefore, the density of the main river can be approximated by the density of clear water, while the density of debris flows should be taken as the density of regional debris flows. S Q is the bulk density of solid materials in a debris flow. P For torrential rain and flood flow; K P For steep slopes in mountainous areas, K is generally used as the confluence coefficient. P =0.7~0.9 (weak surface infiltration, fast runoff velocity), K is generally used in hilly areas. P =0.5~0.7 (medium infiltration and runoff conditions), K in plains or vegetated areasP =0.3~0.5 (strong penetration, slow flow velocity); F i For small watershed B i D. C The congestion coefficient can be obtained by referring to the "Design Flood Calculation Standard for Water Conservancy and Hydropower Projects" (Ministry of Water Resources of the People's Republic of China, 2006) (SL44-2006) in conjunction with on-site investigation; T is the duration of the debris flow at this site (unit: s); L D U represents the length of the main debris flow channel; D S represents the velocity of the debris flow; S represents the slope of the gully bed.

[0150] Finally, the statistics T j Small watershed B in a certain time period i The total volume of debris ejected by the mudslide is taken as T. j Small watershed B in a certain time period i Debris flow erosion (E D ) ij :

[0151]

[0152] In the formula, ρ D The density of the debris flow ejecta is taken as 1.3–1.8 t / m³ for areas dominated by dilute debris flows. 3 The concentration of viscous debris flow in the dominant area is 2.0–2.4 t / m³. 3 The dominant concentration of transitional debris flows is 1.8–2.0 t / m³. 3 ;(V D ) l For T j Small watershed B in a certain time period i The volume of ejecta from the lth debris flow.

[0153] Step S23, gully erosion

[0154] Gully erosion refers to the downcutting, lateral erosion, and headward erosion that occur in gullies under the action of rainwater runoff. For T j Small watershed B in a certain time period i The erosion rate (G) of each gully segment was calculated. g ) ij (t / y) is:

[0155]

[0156] In the formula, (G g ) ij For T j Small watershed B in a certain time period i The erosion rate of the gullies; L s Let r be the length of the s-th segment of the channel. sThe average annual erosion rate of the slope in the gully section (m 2 / y), which is the average annual rate of change of the cross-section of the gully section; ρ is the density of eroded sediment, generally taken as 1.6 t / m³. 3 .

[0157] The annual average rate of change r of the cross section of the channel in equation (11) s Generally, cross-sections of ditches at different locations are extracted and calculated after unified georegistration of multiple DEMs. If conditions permit, they can also be obtained through long-term field monitoring. The annual average rate of change is obtained by dividing the change in cross-sectional area between adjacent periods by the data time interval.

[0158] For gully sections in a stable period (such as flash flood gullies, debris flow gullies, etc., where no major landslides, mudslides, or debris flows have occurred within the time frame of concern), the average annual erosion rate r of the gully section slope is... s The value can be approximated as a constant, meaning that whether the annual average erosion rate of the gully slope is obtained through DEM or on-site monitoring, only data with a short time span is needed.

[0159] T is calculated according to the following formula. j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij :

[0160] (E g ) ij =(G g ) ij ·ΔT (12)

[0161] Step S24, Slope erosion

[0162] Slope erosion in the target watershed was calculated for each grid cell using the modified general soil loss equation (RUSLE). j The soil erosion modulus within a given time period is multiplied by the grid area to obtain the grid scale T. j Soil erosion over a given period. Small watershed B i The slope erosion (E) of this small watershed is obtained by summing the soil erosion of each grid cell within the area. S ) ij . Specifically:

[0163] The soil erosion modulus at the grid scale is calculated as follows:

[0164] A = R·S·L·K·C·P (13)

[0165] In the formula, A is the soil erosion modulus (t / (km²)). 2 ·y); R is the rainfall erosivity factor (MJ / (km) 2·y), calculated based on rainfall data; L and S are dimensionless topographic factors, L is the slope length factor, and S is the slope gradient factor. The L and S factors are extracted based on the digital elevation model of the target area; K is the soil erodibility factor (t / MJ), calculated based on soil property data of the target area; C is the dimensionless vegetation cover factor, obtained based on NDVI data; P is the dimensionless soil and water conservation measures factor, assigned according to slope and land use type.

[0166] T is calculated according to the following formula. j Small watershed B within the time period i Slope erosion (E) S ) ij :

[0167]

[0168] In the formula, A g For the area of ​​a single grid cell, A m For small watershed B i The soil erosion modulus of the m-th grid within the range, where M is B. i Total number of grid cells within a small watershed.

[0169] Step S25, Total Erosion and Distribution of Erosion in the Watershed

[0170] T j Small watershed B within the time period i Total erosion (E) ij The sum of the aforementioned four types of erosion is:

[0171] (E) ij =(E G ) ij +(E D ) ij +(E g ) ij +(E S ) ij (15)

[0172] This also earned T j The spatial distribution of total erosion, gravity erosion, gully erosion, and slope erosion within a watershed, calculated on a small watershed basis, can be obtained by performing the above calculations for different time periods. This yields the spatiotemporal distribution of various types of erosion and total erosion within the target watershed.

[0173] Target watershed in T j The total erosion during the period was:

[0174]

[0175] This allows us to obtain the change in the total erosion of the target area over time.

[0176] Understandably, step S2 comprehensively considers and quantifies the contribution of various erosion types to the erosion of the target watershed, especially quantifying gravity erosion and debris flow erosion, which are usually ignored. Moreover, based on erosion data at the small watershed scale, the spatiotemporal distribution characteristics of various erosions and total erosion in the target watershed can be obtained, which greatly improves the spatiotemporal resolution of watershed erosion characterization.

[0177] In some embodiments, step S3 calculates the sediment yield within the target watershed. Similar to step S2, step S3 also calculates the sediment yield and deposition at the small watershed scale for each of the four erosion types, which are described below:

[0178] Step S31: Gravity erosion-induced sand production and deposition

[0179] First, the mass of the landslide material input into the river is calculated, considering two scenarios: First, if the landslide location is not connected to the river system, the gravity erosion generated by the landslide will not be converted into sediment that can be transported by the water flow; subsequent gully erosion and slope erosion will continue, which will be calculated in the later gully and slope erosion sections and do not need to be repeated here. Second, if the landslide location is connected to the river system, the portion of the material input into the river from a single landslide is calculated using the following formula:

[0180] T G =k G ·ρ·w G ·L G ·h (17)

[0181] h = cQ f (18)

[0182] In the formula, T G The mass of material input into a river from a single landslide; w G L represents the average distance L extends from the riverbank into the water during a landslide. G The length of the river section affected by the landslide; both parameters can be obtained by extracting the landslide area from multiple satellite images; k G The correction factor is typically taken as 0.7-0.8; ρ is the density of eroded sediment; h represents the main river and L... G The average water depth of the corresponding river section; Q is the flow rate of the main river at the location of the landslide, obtained through hydrological data; c and f are coefficients, generally taken as c = 0.25 to 0.55 and f = 0.3 to 0.4.

[0183] Then T j Small watershed B in a certain time period i Deposition amount due to internal gravity erosion (D) G ) ij for:

[0184]

[0185] In the formula, T G ′ for T j Small watershed B in a certain time period i The amount of sediment yield corresponding to the amount of gravity erosion; p and P are respectively T j Small watershed B in a certain time period i Number and total number of landslides connected to the river system within the area.

[0186] Step S32: Sand Production and Deposition from Debris Flow Erosion

[0187] First, calculate T. j Small watershed B in a certain time period i The sediment transport ratio in debris flow erosion refers to the proportion of sediment transported by the river to the volume of debris flow ejected, and is calculated using the following formula:

[0188]

[0189] In the formula, (SDR) D ) ij For T j Small watershed B in a certain time period i The sediment transport ratio of internal debris flow erosion; θ is T j Small watershed B in a certain time period i The angle at which the main ditch flows into the main river is obtained through river system data within the target watershed; γ m and γ D T respectively j Small watershed B in a certain time period i The unit weight of the main river and debris flow; the unit weight of the main river varies little with different time periods and small watersheds, and is generally taken as a constant value; q m and q D T respectively j Small watershed B in a certain time period i The unit width discharge of the main river and debris flow is given. The unit width discharge of the main river is obtained from hydrological data, and the unit width discharge of the debris flow is calculated as q. D =Q D / W D W D For T j Small watershed B in a certain time period i The width of the debris flow channel, Q D For T j Small watershed B in a certain time period i Peak flow rate of debris flow.

[0190] Then, based on the above sediment transport ratio, T is calculated. j Small watershed B in a certain time period i The amount of sediment yield (T) corresponding to the amount of debris flow erosion D )ij and sedimentation amount (D) D ) ij :

[0191] (T D ) ij =(E D ) ij ·(SDR D ) ij (twenty one)

[0192] (D D ) ij =(E D ) ij -(T D ) ij (twenty two)

[0193] Step S33: Sediment Production and Deposition of Gully and Slope Erosion

[0194] Step S331: Calculate the sediment connectivity index at the grid scale within each small watershed:

[0195]

[0196] In the formula, IC is the sediment connectivity index at the grid scale within a small watershed; a larger value indicates higher sediment connectivity. up The upslope component of a small watershed reflects the upstream sediment yield potential; The average impedance factor of the upslope catchment area of ​​a small watershed represents the resistance of surface roughness to water and sediment flow. Let A be the average slope (m / m) of the uphill catchment area of ​​a small watershed; up The upslope catchment area (m²) of a small watershed 2 );D dn d represents the downslope component of a small watershed, reflecting the path resistance of sediment reaching its destination; m W represents the length (m) of the flow path of the m-th grid cell along the steepest downhill direction within a small watershed; m SS represents the impedance factor (local surface roughness) of the m-th grid within a small watershed; m Let be the slope gradient (m / m) of the m-th grid within a certain small watershed.

[0197] Impedance factor W in uphill and downhill component calculations m The surface index IS was calculated based on the roughness index RI, vegetation factor C, and soil and water conservation measure P factor:

[0198]

[0199] In the formula, IS maxThe maximum surface index of the small watershed where the grid is located; the surface index IS of each grid m The calculation is as follows:

[0200] IS m =RI m +C·P (27)

[0201] The roughness index RI of the m-th grating m The calculation is as follows:

[0202]

[0203] In the formula, For use in calculation A raster moving scan pane, x m x represents the elevation of a certain grid cell. s For the area around a certain grille The average elevation of each grid cell. The vegetation factors C and P are the C and P factors that have already been calculated in the RUSLE method when calculating slope erosion (Equation 13).

[0204] Step S332: Calculate the sediment transport ratio

[0205] For gully erosion and slope erosion, the sediment transport ratio refers to the proportion of sediment transported away by rivers to the total amount of erosion.

[0206] For T j During the time period, B for each small watershed is calculated based on the sediment connectivity index IC. i The sediment transport ratio of gully erosion or slope erosion:

[0207]

[0208] In the formula, (SDR) IC ) ij It is T j Small watershed B in a certain time period i Sediment transport ratio of gully erosion or slope erosion; (SDR) max ) ij It is T j Small watershed B in a certain time period i The theoretically achievable maximum sediment transport ratio is related to the topsoil texture, and can generally be taken as 1; IC ij For T j Small watershed B in a certain time period i The average sediment connectivity index is taken as T. j Small watershed B in a certain time period i The mean of the sediment connectivity index at each grid scale; IC0 and k are correction coefficients for calculating the sediment transport ratio and need to be calibrated. When IC ij When =IC0, we have (SDR)IC ) ij =0.5(SDR) max ) ij Therefore, IC0 is (SDR) max ) ij Half of the value corresponds to the sediment connectivity index, which is generally taken as (SDR). max ) ij =1, then IC0 is (SDR) max ) ij =0.5 The sediment connectivity index value corresponding to l needs to be determined by trial calculation; l is generally greater than 0, so we can first take a value between k=1 and 2, substitute it and then calculate the specific value. The trial calculation is stopped when the result is consistent with some observation data on sediment yield at the outlet of a small watershed.

[0209] Step S333: Calculate sediment yield and deposition

[0210] Based on the above sediment transport ratio, T is calculated. j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij Corresponding sediment yield (T) g ) ij and sedimentation amount (D) g ) ij :

[0211] (T g ) ij =(E g ) ij ·(SDR IC ) ij (30)

[0212] (D g ) ij =(E g ) ij -(T D ) ij (31)

[0213] Similarly, T is calculated based on the above sediment transport ratio. j Small watershed B in a certain time period i Slope erosion (E) S ) ij Corresponding sediment yield (T) S ) ij and sedimentation amount (D) S ) ij :

[0214] (T S ) ij =(E S ) ij·(SDR IC ) ij (32)

[0215] (D S ) ij =(E S ) ij -(T S ) ij (33)

[0216] This also earned T j The spatial distribution of sediment yield and deposition corresponding to gravity erosion, debris flow erosion, gully erosion and slope erosion within a watershed, with small watersheds as the unit, is calculated in the above way for different time periods. This allows us to obtain the spatiotemporal distribution of various types of sediment yield and deposition within the target watershed.

[0217] Understandably, step S3 quantifies the sediment yield and deposition corresponding to various erosion types on a small watershed basis, and obtains the spatiotemporal distribution characteristics of sediment yield and deposition in the target watershed, thereby achieving precise location of sediment sources within the watershed.

[0218] In some embodiments, step S4 involves calculating river sediment transport. After calculating erosion, sediment yield, and deposition in all sub-basins within the target watershed for each time period, the sediment transport in the main river system is calculated segment by segment according to the upstream-downstream relationship of the sub-basins' inflow rivers. Considering that coarser bedload has a limited transport distance in the river system, step S4 mainly calculates sediment transport for finer suspended sediment. See [link to relevant documentation]. Figure 3 Specifically, it includes the following steps:

[0219] Based on the distribution of slope, river width, and river type along the course, the rivers in the target basin are divided into X river segments R1, R2, ... R... x ,…R X The slope, width, and shape of each river section do not change significantly. Each river section contains at most one reservoir or lake, and the reservoir or lake is located at the inlet of the river section.

[0220] Calculate the suspended sediment transport in the target basin for each river segment, for T j Any section R within the time period x Its output suspended sediment load (SS) out ) xj for:

[0221]

[0222] In the formula, (SS) in ) xj For T j River section R during the period x The amount of suspended sediment input into the main river from upstream; (I)T ) n River section R x The amount of suspended sediment input into the main river from the nth tributary, where n and N are the river section R, respectively. x The internal tributary numbers and total number are then... T represents j River section R during the time period x The amount of suspended sediment input into the main river from all tributaries within the river; (E B ) xj For T j River section R during the time period x The particle size in the riverbank erosion is consistent with the mass of suspended sediment; (O F ) xj For T j River section R during the time period x The amount of suspended sediment deposited on the floodplain; (O M ) xj For T j River section R during the time period x The amount of artificial sand dredging is determined based on the actual scale of sand dredging in the river channel; (O D ) xj For T j River section R during the time period x The amount of suspended sediment transported away in irrigation or water diversion projects; (O R ) xj For T j River section R during the time period x The amount of suspended sediment in reservoirs or lakes.

[0223] It should be noted that suspended sediment deposition in river systems takes a very long time, generally measured in months or even years. Therefore, suspended sediment deposition in river sections is only considered in two forms: floodplain deposition and reservoir / lake deposition.

[0224] Among them, the suspended sediment load I from a tributary within a single river section, calculated in step S3 based on the sediment yield of the small watershed, is... T The calculation is as follows:

[0225] I T =T G ′·(Δ s ) G +T D ·(Δ s ) D +T g ·(Δ s ) g +T S (35)

[0226] In the formula, T G′ represents the sediment yield corresponding to the gravity erosion of a specific tributary within a single river segment, taken as the total mass of material input into the river from all landslides and collapses connected to the river system within that specific tributary; T D T represents the sediment yield corresponding to the debris flow erosion volume of a specific tributary within a single river section, in a specific watershed. g T represents the sediment yield corresponding to the erosion of a specific tributary within a single river section in a small watershed; S This refers to the sediment yield corresponding to the slope erosion of a specific tributary within a single river section, specifically for a small watershed; (Δ) s ) G 、(Δ s ) D 、(Δ s ) g T respectively G ′、T D and T g The proportion of suspended sediment was obtained by extracting the proportion of characteristic suspended sediment particle size (e.g., 0.05 mm) of the target watershed from the gradation curves of landslide deposits, debris flow fan deposits, and gully slope materials.

[0227] T j River section R during the time period x The particle size of the riverbank erosion is consistent with the mass of suspended sediment (E). B ) xj Based on the calculation of water flow work:

[0228] (EB) xj =b(ρ w g(Q B ) xj S xj (h) B ) xj (L B ) xj (ρ B ) xj ((Δ s ) B ) xj (36)

[0229] In the formula, b is an adjustment parameter used to adjust the calculation results to conform to the actual situation; the variable with the subscript x represents the river segment R. x Average value, where the subscript j represents the time period number; ρ w Where is the density of pure water; g is the acceleration due to gravity; Q B The discharge at the riverbank is ρ, which can be approximated as the flood discharge with a return period of 1 to 2 years in the absence of measured data; S is the river slope, ρ is the slope of the river section. w g(Q B ) xj S xj That is, Tj River section R during the time period x water flow work; h B L is the height of the riverbank. B ρ is the length of the river segment. B For the density of the material on the shore, (Δ s ) B This represents the proportion of suspended sediment in the material along the riverbank.

[0230] T j River section R during the time period x The amount of suspended sediment deposited on the floodplain (O F ) xj The calculation is as follows:

[0231]

[0232] In the formula, (Q f ) xj For T j River section R during the time period x The average discharge of the inland river flowing through the floodplain, i.e., T j In all floods during a given period where the peak flow in the river segment exceeded the average flow at the floodplain, the peak flow exceeded the average of the average flow. xj For T j River section R during the time period x Average settling velocity of suspended sediment; (A) f ) xj For T j River section R during the time period x The average area of ​​the floodplain within the river.

[0233] T j River section R during the time period x The amount of suspended sediment transported away in irrigation or water diversion projects (O D ) xj The calculation is as follows:

[0234] (O D ) xj =(Q D ) xj ·ΔT·(C D ) xj (38)

[0235] In the formula, (Q D ) xj For T j River section R during the time period x The average output flow rate in irrigation or water diversion projects, (C D ) xj For T j River section R during the time period xThe average sediment content of the output water in irrigation or water diversion projects is obtained through the actual operation of the irrigation or water diversion projects.

[0236] If hydrological and sediment monitoring data are available at the inlet and outlet of a reservoir or lake, the sedimentation volume can be directly obtained from the data as T. j River section R during the time period x Suspended sediment deposition in reservoirs or lakes (O R ) xj If not, then T j River section R during the time period x Suspended sediment deposition in reservoirs or lakes (O R ) xj The calculation is as follows:

[0237] (O R ) xj =(SS) in ) xj ·TE xj (39)

[0238] In the formula, TE xj For T j River section R during the time period x The average sediment retention rate of a reservoir or lake is calculated as follows:

[0239]

[0240] In the formula, C R The effective storage capacity of a reservoir or lake (10 3 *m 3 ), I R The average annual runoff of a reservoir or lake (10 3 *m 3 ).

[0241] It is understood that the embodiments of the present invention can obtain the distribution of suspended sediment transport along the course of the river system in the target watershed, and quantitatively characterize the natural process of erosion and sediment production and the impact of artificial facilities such as sand mining, irrigation, and reservoirs on suspended sediment transport.

[0242] A watershed sediment estimation device provided in a second aspect embodiment of the present invention includes:

[0243] The basic data acquisition module is configured to collect basic data of the target watershed, including rainfall, soil, vegetation, topography, orthophotos and hydrological data. It organizes various basic data into a grid form and performs unified spatial registration. It sets the watershed boundary as the spatial unit for sediment estimation, spatially divides various basic data based on the watershed boundary, and divides various basic data at the watershed scale into time periods based on the time scale requirements of sediment estimation.

[0244] The erosion calculation module is configured to calculate erosion for each small watershed according to different erosion types, namely gravity erosion, debris flow erosion, gully erosion, and slope erosion, and obtain the spatiotemporal distribution of various types of erosion and total erosion within the target watershed.

[0245] The sediment yield and deposition calculation module is configured to calculate the sediment yield and deposition corresponding to various erosion amounts at the small watershed scale. Specifically, for gravity erosion, the sediment yield is calculated based on the amount of material input into the river from landslides connected to the water system, and the deposition amount of gravity erosion at the small watershed scale is obtained by subtracting the sediment yield from the gravity erosion amount. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is calculated first, and then the sediment yield and deposition amount at the small watershed scale are calculated based on various sediment transport ratios. For debris flow erosion, the sediment transport ratio at the small watershed scale is calculated based on the bulk density, flow rate, and inflow angle of debris flow and the main river. For gully erosion and slope erosion, the sediment transport ratio at the small watershed scale is calculated based on the sediment connectivity index at the grid scale within each small watershed. Based on the sediment yield and deposition amounts of various erosions at the small watershed scale, the spatiotemporal distribution of sediment yield and deposition amounts in the target watershed is obtained.

[0246] The suspended sediment transport calculation module is configured to calculate the suspended sediment transport in the main river system segment by segment based on the sediment yield of all sub-basins in the target watershed at each time period. It calculates the suspended sediment transport in the sub-basins in the main river system segment by segment according to the upstream and downstream relationship of the confluence rivers of each sub-basin in the target watershed. It also combines the sand dredging, reservoir siltation, and the input and output of suspended sediment in the river section to obtain the distribution of suspended sediment transport along the flow direction of the main river system.

[0247] It should be noted that the foregoing explanation of the embodiments of the watershed sediment estimation method also applies to the watershed sediment estimation device of this embodiment, and will not be repeated here.

[0248] To implement the above embodiments, this invention also proposes a computer-readable storage medium storing a computer program that is executed by a processor to perform the watershed sediment estimation method of the above embodiments.

[0249] The following is for reference. Figure 4 The diagram illustrates a structural schematic of an electronic device suitable for implementing embodiments of the present invention. It should be noted that the electronic device in the embodiments of the present invention may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), and in-vehicle terminals (e.g., in-vehicle navigation terminals), as well as fixed terminals such as digital TVs, desktop computers, and servers. Figure 4The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments of the present invention.

[0250] like Figure 4 As shown, the electronic device may include a processing unit (e.g., a central processing unit, a graphics processing unit, etc.) 101, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 102 or a program loaded from a storage device 108 into a random access memory (RAM) 103. The RAM 103 also stores various programs and data required for the operation of the electronic device. The processing unit 101, ROM 102, and RAM 103 are interconnected via a bus 104. An input / output (I / O) interface 105 is also connected to the bus 104.

[0251] Typically, the following devices can be connected to I / O interface 105: input devices 106 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, etc.; output devices 107 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 108 including, for example, magnetic tapes, hard disks, etc.; and communication devices 109. Communication device 109 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 4 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown. More or fewer devices may be implemented or have alternatively.

[0252] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, this embodiment includes a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such an embodiment, the computer program can be downloaded and installed from a network via a communication device 109, or installed from a storage device 108, or installed from a ROM 102. When the computer program is executed by the processing device 101, it performs the functions defined in the methods of the embodiments of the present invention.

[0253] It should be noted that the computer-readable medium described above in this invention can be a computer-readable signal medium, a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this invention, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0254] The aforementioned computer-readable medium may be included in the aforementioned electronic device; or it may exist independently and not assembled into the electronic device.

[0255] The aforementioned computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to perform the aforementioned watershed sediment estimation method.

[0256] Computer program code for performing the operations of this invention can be written in one or more programming languages ​​or a combination thereof. These programming languages ​​include object-oriented programming languages—such as Java, Smalltalk, C++, and Python—as well as conventional procedural programming languages—such as the "C-" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0257] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0258] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0259] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0260] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0261] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0262] Those skilled in the art will understand that implementing all or part of the steps of the methods in the above embodiments can be accomplished by instructing related hardware through a program. The developed program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0263] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0264] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A method for estimating watershed sediment load, characterized in that, include: Step S1: Collect basic data of the target watershed, including rainfall, soil, vegetation, topography, orthophotos and hydrological data. Organize the various basic data into a grid and perform unified spatial registration. Set the watershed boundary as the spatial unit for sediment estimation. Based on the watershed boundary, spatially divide the various basic data. Based on the time scale requirements of sediment estimation, divide the various basic data at the watershed scale into time periods. Step S2: For each small watershed, calculate the erosion amount according to different erosion types, namely gravity erosion, debris flow erosion, gully erosion, and slope erosion, to obtain the spatiotemporal distribution of various erosion amounts and the total erosion amount within the target watershed; among which, To address gravity erosion, T is identified through multi-period orthophotos of the watershed. j The newly added landslide area during the period, based on the statistics of the landslide area T j Small watershed B in a certain time period i The total volume of material released by the collapse and landslide within the area, as T j Small watershed B in a certain time period i Gravitational erosion (E) G ) ij T j The time unit is determined based on the estimated sediment demand, and the duration ΔT is the same for each time period; To address debris flow erosion, the first step is to obtain data from small watershed B based on rainfall data. i During time period T j Information on all valid rainfall events within the timeframe, including the duration and average intensity of each event, is used to determine whether each event triggers a debris flow based on a rainfall threshold trigger condition. If an event is determined not to trigger a debris flow, its outflow volume is set to 0; if it is determined to trigger a debris flow, its outflow volume is calculated. The T-value is then statistically analyzed. j Small watershed B in a certain time period i The total volume of debris ejected by the mudslide is taken as T. j Small watershed B in a certain time period i Debris flow erosion (E D ) ij ; To address gully erosion, T j Small watershed B in a certain time period i The gully is divided into several gully segments. The gully erosion rate of each segment is calculated, and T is calculated based on the gully erosion rate. j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij ; To address slope erosion, the T value for each grid cell was calculated by modifying the general soil loss equation RUSLE. j The soil erosion modulus within a given time period is multiplied by the grid area to obtain the grid scale T. j Soil erosion over a period of time; small watershed B i T is obtained by summing the soil erosion of each grid within the range. j Small watershed B in a certain time period i Slope erosion (E) S ) ij ; The summation of the four types of erosion measurements yields T. j Small watershed B within the time period i Total erosion (E) ij ; Step S3: For gravity erosion, calculate the sediment yield based on the amount of material input into the river from the landslides connected to the water system, and subtract the sediment yield from the gravity erosion amount to obtain the sedimentation amount of gravity erosion at the small watershed scale. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is first calculated separately. Then, the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. Specifically, the sediment transport ratio at the small watershed scale for debris flow erosion is calculated based on the bulk density, flow rate, and inflow angle of the debris flow and the main river. The sediment transport ratio at the small watershed scale for gully erosion and slope erosion is calculated based on the sediment connectivity index at the grid scale within each small watershed. The spatiotemporal distribution of sediment yield and sedimentation in the target watershed is obtained based on the sediment yield and sedimentation of various types of erosion at the small watershed scale. Step S4: Based on the sediment yield of all sub-basins in the target basin calculated in Step S3, calculate the suspended sediment transport of the sub-basins in the main river system segment by segment according to the upstream and downstream relationship of the confluence rivers of each sub-basin in the target basin. Combine the sand dredging, reservoir siltation, and the input and output of suspended sediment in the river section to obtain the distribution of suspended sediment transport along the flow direction of the main river system.

2. The watershed sediment estimation method according to claim 1, characterized in that, The basic data collected in step S1 includes rainfall data with a temporal resolution of no less than 3 hours, soil data including the organic matter content in sand, silt, and clay of the topsoil, vegetation data including the normalized difference vegetation index and vegetation type, topographic data using a digital elevation model with a spatial resolution of no less than 30 meters, and hydrological data including river system data, flow, runoff, and sediment transport information within the target watershed. The basic data also includes land use types for calculating dimensionless soil and water conservation factors. The spatial resolution used for unified spatial registration of basic data for various grid types is consistent with the spatial resolution of the digital elevation model. The sub-basin is the basin corresponding to the smallest order of rivers in Horton's Law. Based on the digital elevation model, the target basin is divided into I sub-basins B1, B2, ... B1. i ,…B I The area, topographic elevation difference, average slope, channel length, channel width, and channel slope of each small watershed were statistically analyzed.

3. The watershed sediment estimation method according to claim 1, characterized in that, T is calculated according to the following formula. j Small watershed B in a certain time period i Gravitational erosion (E) G ) ij : In the formula, ρ G The density of the collapsed and landslide material; (V) G ) k For T j Small watershed B in a certain time period i The mass of material released by the k-th landslide, where K is T. j Small watershed B in a certain time period i Total number of internal collapses and landslides; volume V of material released by a single collapse or landslide. G Calculate according to the following formula: In the formula, A G The area of ​​a single landslide is denoted by α and γ, where α is 0.05 ± 0.02, γ is 1.1 to 1.3 for soil landslides, and γ is 1.3 to 1.6 for rock landslides. The small watershed B i During time period T j All valid rainfall events within the area can be obtained using the following steps: First, the rainfall data after spatial division is used to calculate the rainfall in each time period t of the small watershed according to the following formula. τ Average rainfall within: In the formula, For small watershed B i During time period t τ Average rainfall within, t τ M represents the temporal resolution of the rainfall data, and M represents the watershed B. i The total number of grid cells within, For small watershed B i The m-th grid cell in the time period t τ The amount of rainfall; Small watershed B i During time period t τ average rainfall Divide by the time period t τ As a small watershed B i During time period t τ The average rainfall intensity; Iterate through each time period T j We obtained the time series matrix of rainfall intensity for each small watershed, and then determined the intensity of each small watershed in each time period T in chronological order. j The rainfall intensity is used to determine the start of a valid rainfall event. A valid rainfall event begins when the rainfall intensity exceeds a first preset value, and ends when the rainfall intensity falls below the first preset value but continues for at least a second preset value. A valid rainfall event is defined as the period during which the rainfall intensity continuously exceeds the first preset value. The duration D and average rainfall intensity of each valid rainfall event are recorded. Thus, obtain small watershed B i During time period T j Information on all valid rainfall events within the region; The method of determining whether each effective rainfall event triggers a debris flow based on rainfall threshold triggering conditions is as follows: Let the rainfall threshold be I c The following formula is used to calculate the results on a small watershed basis: I c =a D D -β In the formula, α D Both β and β are constants; When the average rainfall intensity of an effective rainfall event At that time, it was considered that no mudslide would be triggered; When the average rainfall intensity of an effective rainfall event At that time, it was considered that a debris flow was triggered, and the statistics of small watershed B were compiled. i In T j Rainfall data for each event that could trigger mudslides during the specified period. Where l represents the rainfall event number that will trigger a mudslide, with a total of L events, D l and Small watershed B i In T j The duration and average rainfall intensity of the l-th rainfall event that will trigger debris flows within the time period are determined, and the volume of debris ejecta V of each debris flow is calculated using the following formula. D : In the formula, Q D γ is the peak flow rate of the debris flow; D The density of debris flow; γ W The density of pure water; γ S Q is the bulk density of solid materials in a debris flow. P For torrential rain and flood flow; K P F is the confluence coefficient; i For small watershed B i D. C The congestion coefficient is represented by T, the duration of a mudslide, and L. D U represents the length of the main debris flow channel; D S represents the velocity of the debris flow; S represents the slope of the gully bed. The T j Small watershed B in a certain time period i Debris flow erosion (E D ) ij Calculate according to the following formula: In the formula, ρ D Density of debris ejected from the debris flow; (V) D ) l For T j Small watershed B in a certain time period i The volume of ejecta from the first debris flow in the inner zone; The T j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij Calculate according to the following formula: (E g ) ij =(G g ) ij ·ΔT In the formula, L s r is the length of the s-th segment of the channel; s Let be the average annual erosion rate of the slope of the gully section, and be the average annual rate of change of the cross section of the gully section; ρ is the density of eroded sediment; ΔT is the temperature of T. j Duration of the period; The T j Small watershed B within the time period i Slope erosion (E) S ) ij Calculate according to the following formula: In the formula, A g A represents the area of ​​a single grid cell. m For small watershed B i The soil erosion modulus of the m-th grid within the range; M is the watershed B. i The total number of grid cells within.

4. The watershed sediment estimation method according to claim 1, characterized in that, In step S3, Regarding sediment production and deposition from gravity erosion, if the landslide location is not connected to a river system, the sediment production and deposition from gravity erosion caused by the landslide are both zero. If the landslide location is connected to a river system, then the T... j Small watershed B in a certain time period i Deposition amount due to internal gravity erosion (D) G ) ij Calculate according to the following formula: (D G ) ij =(E G ) ij -T′ G T G =k G ·ρ·w G ·L G ·h h=cQ f In the formula, (E G ) ij For T j Small watershed B in a certain time period i The amount of gravitational erosion; p and P are respectively T j Small watershed B in a certain time period i Numbering and total number of landslides connected to the river system within the area; T G The mass of material input into a river from a single landslide; w G L represents the average distance a single landslide extends from the riverbank into the water, obtained based on historical remote sensing imagery or field surveys. G k represents the length of the river segment affected by a single landslide. G ρ is the correction factor; h is the density of eroded sediment; ρ is the density of L. G The average water depth of the corresponding river section; Q is the flow rate of the main river at a single landslide location; c and f are both coefficients; T G ′ for T j Small watershed B in a certain time period i The amount of sediment yield corresponding to the amount of gravity erosion; To determine the sediment production and deposition from debris flow erosion, T is first calculated using the following formula. j Small watershed B in a certain time period i Sediment transport ratio (SDR) of internal debris flow erosion D ) ij : In the formula, θ is T j Small watershed B in a certain time period i The angle at which the main ditch flows into the main river; γ m and γ D T respectively j Small watershed B in a certain time period i The bulk density of the main river and debris flows; q m and q D T respectively j Small watershed B in a certain time period i The unit width discharge of the main river and the debris flow are given. The unit width discharge of the main river is obtained from hydrological data, and the unit width discharge of the debris flow is calculated as q. D =Q D / w D w D For T j Small watershed B in a certain time period i The width of the debris flow channel, Q D For T j Small watershed B in a certain time period i Peak flow rate of debris flow; Then based on the sediment transport ratio (SDR) D ) ij Calculate T j Small watershed B in a certain time period i Debris flow erosion results in sediment yield and deposition: (T D ) ij =(E D ) ij ·(SDR D ) ij (D D ) ij =(E D ) ij -(T D ) ij In the formula, (T) D ) ij For T j Small watershed B in a certain time period i The amount of sediment produced by debris flow erosion, (D D ) ij For T j Small watershed B in a certain time period i The amount of sediment eroded by debris flows; To address sediment production and deposition in gully and slope erosion, T is first calculated based on the sediment connectivity index at the grid scale within each small watershed. j Small watershed B in a certain time period i Sediment transport ratio (SDR) of gully erosion or slope erosion IC ) ij : In the formula, (SDR) max ) ij It is T j Small watershed B in a certain time period i The theoretically achievable maximum sediment transport ratio is related to the topsoil texture; IC ij For T j Small watershed B in a certain time period i The average sediment connectivity index is taken as T. j Small watershed B in a certain time period i The mean value of the sediment connectivity index at each grid scale within the grid; IC0 and k are correction factors for calculating the sediment transport ratio; Then based on the sediment transport ratio (SDR) IC ) ij Calculate T j Small watershed B in a certain time period i The sediment yield and deposition corresponding to gully erosion, and the sediment yield and deposition corresponding to slope erosion: (T g ) ij =(E g ) ij ·(SDR IC ) ij (D g ) ij =(E g ) ij -(T D ) ij (T S ) ij =(E S ) ij ·(SDR IC ) ij (D S ) ij =(E S ) ij -(T S ) ij In the formula, (E g ) ij For T j Small watershed B in a certain time period i The amount of gully erosion, (T g ) ij and (D) g ) ij T respectively j Small watershed B in a certain time period i The corresponding sediment yield and deposition amount for gully erosion; (E S ) ij For T j Small watershed B in a certain time period i The amount of slope erosion, (T) S ) ij and (D) S ) ij T respectively j Small watershed B in a certain time period i The amount of sand production and deposition corresponding to the amount of slope erosion.

5. The watershed sediment estimation method according to claim 4, characterized in that, Let IC be the sediment connectivity index at the grid scale within a small watershed, and calculate it according to the following formula: IS m =RI m +C·P In the formula, D up The upslope component of a small watershed reflects the upstream sediment yield potential; The average impedance factor of the upslope catchment area of ​​a small watershed represents the resistance of surface roughness to water and sediment flow. A represents the average slope of the uphill catchment area of ​​a small watershed. up D represents the area of ​​the upslope catchment area of ​​a small watershed; dn d represents the downslope component of a small watershed, reflecting the path resistance of sediment reaching its destination; m W represents the length of the flow path along the steepest downhill direction for the m-th grid cell within a small watershed; m Let SS be the impedance factor of the m-th grid within a certain small watershed; m IS represents the slope gradient of the m-th grid cell within a small watershed; max IS represents the maximum surface index of the small watershed where the raster is located. m RI is the surface index of the m-th grid cell within a small watershed. m Let f be the roughness index of the m-th grid cell within a certain small watershed; To calculate RI m Used A raster moving scan pane, x m x represents the elevation of a certain grid cell. s For the area around a certain grille The average elevation of each grid cell; C is the dimensionless vegetation cover factor; P is the dimensionless soil and water conservation measure factor.

6. The watershed sediment estimation method according to claim 1, characterized in that, Step S4 specifically includes: Based on the distribution of slope, river width, and river type along the course, the rivers in the target basin are divided into X river segments R1, R2, ... R... x ,…R X The regulations stipulate that at most one reservoir or lake shall be provided in each section of the river, and that the reservoir or lake shall be located at the inlet of the river section. Calculate the suspended sediment transport in the target basin for each river segment, for T j Any section R within the time period x Its output suspended sediment load (SS) out )x j for: In the formula, (SS) in ) xj For T j River section R during the period x The amount of suspended sediment input into the main river from upstream; (I T ) n River section R x The amount of suspended sediment input into the main river from the nth tributary, where n and N are the river section R, respectively. x The internal tributary numbers and total number are then... T represents j River section R during the time period x The amount of suspended sediment input into the main river from all tributaries within the river section R x The amount of suspended sediment I input from a tributary into the main river T The sediment yield of the small watershed obtained in step S3 is calculated; (E) B ) xj For T j River section R during the time period x The particle size in the riverbank erosion is consistent with the mass of suspended sediment, calculated based on the work done by the water flow; (O F ) xj For T j River section R during the time period x The amount of suspended sediment deposited on the floodplain, based on T j River section R during the time period x The average discharge, average settling velocity of suspended sediment, and average area of ​​the floodplain were calculated. (O) D ) xj For T j River section R during the time period x The amount of suspended sediment transported away in irrigation or water diversion projects, based on T j River section R during the time period x The average output flow rate and average sediment content of the output water flow are calculated in irrigation or water diversion projects; (O R ) xj For T j River section R during the time period x The amount of suspended sediment deposited in reservoirs or lakes is obtained based on hydrological sediment observation data, or based on T... j River section R during the period x Suspended sediment load (SS) input into the main river from upstream in ) xj It is calculated based on the average sediment retention rate of reservoirs or lakes.

7. The watershed sediment estimation method according to claim 6, characterized in that, The amount of suspended sediment (I) input into the main river from a tributary within a single river segment is calculated using the following formula. T : I T =T G ′·(Δ s ) G +T D ·(Δ s ) D +T g ·(Δ s ) g +T S In the formula, T G ′ for T j Small watershed B in a certain time period i The amount of sediment yield corresponding to the amount of gravity erosion; T D T represents the sediment yield corresponding to the debris flow erosion volume of a specific tributary within a single river section, in a specific watershed. g T represents the sediment yield corresponding to the erosion of a specific tributary within a single river section in a small watershed; S This refers to the sediment yield corresponding to the slope erosion of a specific tributary within a single river section, specifically for a small watershed; (Δ) s ) G 、(Δ s ) D 、(Δ s ) g T respectively G ′、T D and T g The proportion of suspended sediment was obtained by extracting the characteristic particle size proportion of suspended sediment in the target watershed from the gradation curves of landslide deposits, debris flow fan deposits, and gully slope materials. T is calculated according to the following formula. j River section R during the time period x The particle size of the riverbank erosion is consistent with the mass of suspended sediment (E). B ) xj : (E B ) xj =b(ρ w g(Q B ) xj S xj )(h B ) xj (L B ) xj (r B ) xj (B) xj ((D s ) B ) xj In the formula, b is the adjustment parameter; the variable with the subscript x represents the river segment R. x Average value, where the subscript j represents the time period number; ρ w Where is the density of pure water; g is the acceleration due to gravity; Q B S is the discharge at the river's flat beach; S is the river's slope; h B L represents the height of the riverbank. B ρ is the length of the river segment; B The density of the material on the shoreline; (Δ s ) B The proportion of suspended sediment in the material along the riverbank; T is calculated according to the following formula. j River section R during the time period x The amount of suspended sediment deposited on the floodplain (O F ) xj : In the formula, (O f ) xj For T j River section R during the time period x The average discharge of the inland river flowing through the floodplain, i.e., T j In all floods during a given period where the peak flow in the river segment exceeded the average flow at the floodplain, the peak flow exceeded the average of the average flow. xj For T j River section R during the time period x Average settling velocity of suspended sediment; (A) f ) xj For T j River section R during the time period x The average area of ​​the floodplain within the area; T is calculated according to the following formula. j River section R during the time period x The amount of suspended sediment transported away in irrigation or water diversion projects (O D ) xj : (Oh D ) xj =(Q D ) xj ·ΔT·(C D ) xj In the formula, (Q D ) xj For T j River section R during the time period x The average output flow rate in irrigation or water diversion projects, (C D ) xj For T j River section R during the time period x The average sediment content of the output water flow in irrigation or water diversion projects; For situations where there is no hydrological and sediment monitoring data at the inlet or outlet of a reservoir or lake, T is calculated using the following formula. j River section R during the time period x Suspended sediment deposition in reservoirs or lakes (O R ) xj : (Oh R ) xj =(SS in ) xj ·THE xj In the formula, TE xj For T j River section R during the time period x The average sediment retention rate of a reservoir or lake; C R The effective storage capacity of a reservoir or lake; I R This refers to the average annual runoff of a reservoir or lake.

8. A watershed sediment estimation device, characterized in that, include: The basic data acquisition module is configured to collect basic data of the target watershed, including rainfall, soil, vegetation, topography and hydrological data, organize various basic data into grid form and perform unified spatial registration, set the small watershed boundary as the spatial unit for sediment estimation, spatially divide various basic data based on the small watershed boundary, and divide various basic data at the small watershed scale into time periods based on the time scale requirements of sediment estimation. The erosion calculation module is configured to calculate erosion for each small watershed according to different erosion types, namely gravity erosion, debris flow erosion, gully erosion, and slope erosion, obtaining the spatiotemporal distribution of various erosion amounts and total erosion within the target watershed; among which... To address gravity erosion, T is identified through multi-period orthophotos of the watershed. j The newly added landslide area during the period, based on the statistics of the landslide area T j Small watershed B in a certain time period i The total volume of material released by the collapse and landslide within the area, as T j Small watershed B in a certain time period i Gravitational erosion (E) G ) ij T j The time unit is determined based on the estimated sediment demand, and the duration ΔT is the same for each time period; To address debris flow erosion, the first step is to obtain data from small watershed B based on rainfall data. i During time period T j Information on all valid rainfall events within the timeframe, including the duration and average intensity of each event, is used to determine whether each event triggers a debris flow based on a rainfall threshold trigger condition. If an event is determined not to trigger a debris flow, its outflow volume is set to 0; if it is determined to trigger a debris flow, its outflow volume is calculated. The T-value is then statistically analyzed. j Small watershed B in a certain time period i The total volume of debris ejected by the mudslide is taken as T. j Small watershed B in a certain time period i Debris flow erosion (E D ) ij ; To address gully erosion, T j Small watershed B in a certain time period i The gully is divided into several gully segments. The gully erosion rate of each segment is calculated, and T is calculated based on the gully erosion rate. j Small watershed B in a certain time period i The amount of gully erosion (E) g ) ij ; To address slope erosion, the T value for each grid cell was calculated by modifying the general soil loss equation RUSLE. j The soil erosion modulus within a given time period is multiplied by the grid area to obtain the grid scale T. j Soil erosion over a period of time; small watershed B i T is obtained by summing the soil erosion of each grid within the range. j Small watershed B in a certain time period i Slope erosion (E) S ) ij ; The summation of the four types of erosion measurements yields T. j Small watershed B within the time period i Total erosion (E) ij ; The sediment yield and deposition calculation module is configured to calculate the sediment yield and deposition corresponding to various erosion amounts at the small watershed scale. Specifically, for gravity erosion, the sediment yield is calculated based on the amount of material input into the river from landslides connected to the water system, and the deposition amount of gravity erosion at the small watershed scale is obtained by subtracting the sediment yield from the gravity erosion amount. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is calculated first, and then the sediment yield and deposition amount at the small watershed scale are calculated based on various sediment transport ratios. For debris flow erosion, the sediment transport ratio at the small watershed scale is calculated based on the bulk density, flow rate, and inflow angle of debris flow and the main river. For gully erosion and slope erosion, the sediment transport ratio at the small watershed scale is calculated based on the sediment connectivity index at the grid scale within each small watershed. Based on the sediment yield and deposition amounts of various erosions at the small watershed scale, the spatiotemporal distribution of sediment yield and deposition amounts in the target watershed is obtained. The suspended sediment transport calculation module is configured to calculate the suspended sediment transport in the main river system segment by segment based on the sediment yield of all sub-basins in the target watershed at each time period. It calculates the suspended sediment transport in the sub-basins in the main river system segment by segment according to the upstream and downstream relationship of the confluence rivers of each sub-basin in the target watershed. It also combines the sand dredging, reservoir siltation, and the input and output of suspended sediment in the river section to obtain the distribution of suspended sediment transport along the flow direction of the main river system.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the watershed sediment estimation method according to any one of claims 1 to 7.

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