Basin sediment rough calculation method and device and storage medium

Abstract

The invention provides a basin sediment budget calculation method, which comprises the following steps of: arranging various types of collected basic data of a target basin into a grid form, carrying out uniform space registration, and dividing the various types of basic data based on a small basin boundary serving as a space unit of sediment budget calculation; for each small watershed, respectively calculating gravitational erosion, debris flow erosion, channel erosion and slope erosion to obtain spatial and temporal distribution of various erosion amounts and the total erosion amount in the target watershed; respectively calculating the sediment yield and the deposition rate of the small watershed scale aiming at the four types of erosion; on the basis of the calculated sediment production, the sediment transport amount of the small watershed suspended load in the main river water system is calculated section by section according to the upstream and downstream relation of the convergence river position of each small watershed in the target watershed, and distribution of the sediment transport amount of the suspended load in the flowing direction of the main river water system is obtained in combination with sand digging, reservoir sedimentation and the input amount and the output amount of the suspended load in the river reach. According to the method, the sediment space-time distribution in the basin erosion and basin sand-producing river sediment transportation multi-physical process can be comprehensively quantified.

Description

Technical Field

[0001] The present invention belongs to the fields of watershed environmental management, soil and water conservation, mountain disasters and environment, remote sensing information technology, and in particular relates to a watershed sediment estimation method, device and storage medium. Background Art

[0002] Watershed erosion is a geomorphic process in which surface material in a watershed shifts under the influence of external forces. The material produced by watershed erosion enters the river system as sediment, which is transported downstream or deposited in the river channel. Watershed erosion and sediment transport are key physical processes in watershed geomorphic evolution and landform shaping, and they also have a profound impact on human economic and social activities within the watershed. Although erosion and sediment production, sediment transport, sediment deposition, and output from the watershed are continuous physical processes, current research on watershed erosion, 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, focusing primarily on erosion processes on slopes, while sediment transport is generally a focus of water conservancy projects and river geomorphology, and has a weaker connection to the sediment replenishment of river channels by slope erosion. However, with climate change and increased human activity, coupled water-sediment disasters are becoming increasingly common, and the need to understand the temporal and spatial distribution patterns of erosion and sedimentation at the basin level is growing stronger. For example, extreme basin-wide flood disasters are often linked to upstream processes such as extreme rainfall, runoff generation, flash floods, and debris flows, as well as flood evolution. Therefore, prevention and control cannot be limited to urban areas in the middle and lower reaches, but must encompass the entire basin. For another example, basin-wide erosion, sediment production, and sediment transport significantly impact the construction, operation, and maintenance of water conservancy and hydropower projects within and downstream of the basin, particularly reservoir siltation. Understanding the temporal and spatial distribution of erosion and sediment transport within the basin can effectively facilitate the identification of sediment sources and the design and implementation of targeted soil and water conservation measures.

[0003] Sediment estimation is a method for studying erosion, sediment transport, sediment deposition, and sediment distribution within a watershed. It organically integrates slope erosion processes with river sediment transport processes, breaking through the traditional disciplinary divide between soil and water conservation and water conservancy engineering. This method rapidly reveals the spatiotemporal distribution of erosion and sediment transport within a watershed, providing strong scientific support for watershed-scale soil and water conservation, river evolution, disaster prevention and mitigation, and sustainable development. However, existing sediment estimation methods suffer from the following problems: First, they primarily consider slope erosion, while paying less attention to gravity erosion (gravity-unloading processes such as collapses and landslides), debris flow erosion, and gully erosion, which are common and concentrated sediment-producing processes in the marginal regions of the Qinghai-Tibet Plateau. Quantitative descriptions are often lacking, or these descriptions rely heavily on field observations, which are both difficult and costly. Second, sediment yield calculations are primarily based on the sediment delivery ratio (the ratio of sediment transported at the watershed outlet to the total erosion in the watershed). However, this ratio is often empirically derived, exhibits significant local variation, and lacks a widely applicable quantitative calculation method. In view of the actual needs of the aforementioned basin sediment estimation and the problems existing in the existing methods, it is necessary to develop a special basin sediment estimation method. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings and deficiencies of existing basin sediment estimation methods and propose a method that comprehensively quantifies the spatiotemporal distribution of sediment across multiple physical processes, including basin erosion and sediment transport in sediment-producing rivers. This method comprehensively considers and quantifies different types of erosion, provides a method for calculating sediment transport ratios for each type of erosion, and ultimately quantifies the sediment transport process in rivers. This method can provide technical support for comprehensive basin management and has significant potential for widespread application.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A first aspect of the present invention provides a method for estimating sediment in a watershed, comprising:

[0007] Step S1: Collect basic data of the target watershed, including rainfall, soil, vegetation, topography, orthophotos, and hydrological data; organize various basic data into a grid format and perform unified spatial registration; set small watershed boundaries as the spatial unit for sediment estimation; spatially divide various basic data based on the small watershed boundaries; and divide various basic data at the small watershed scale into time periods based on the time scale requirements of sediment estimation;

[0008] 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, and obtain the spatiotemporal distribution of each type of erosion amount and the total erosion amount in the target watershed;

[0009] Step S3: For gravity erosion, the sediment yield is calculated based on the volume of river material input from landslides and collapses connected to the water system, and the sediment yield is subtracted from the gravity erosion volume to obtain the sedimentation volume 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. Then, the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. The small watershed-scale sediment transport ratio 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 small watershed-scale sediment transport ratios for gully erosion and slope erosion are calculated based on the grid-scale sediment connectivity index within each small watershed.

[0011] The temporal and spatial distribution of sediment yield and sedimentation in the target watershed is obtained based on the sediment yield and sedimentation of various erosion factors at the small watershed scale;

[0012] Step S4: Based on the sediment yield of all small watersheds in the target watershed calculated in step S3 during each time period, the suspended sediment transport of the small watersheds in the main river system is calculated section by section according to the upstream and downstream relationship of the locations where each small watershed in the target watershed flows into the river. The distribution of the suspended sediment transport along the flow direction of the main river system is obtained by combining dredging, reservoir siltation, and the input and output of suspended sediment in the river section.

[0013] In some embodiments, the basic data collected in step S1 include rainfall data with a temporal resolution of no less than 3 hours, soil data including organic matter content in sand, silt, and clay in the surface soil, vegetation data including normalized vegetation index and vegetation type, terrain 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 type for calculation of dimensionless soil and water conservation measures factors. The spatial resolution used in performing unified spatial registration on basic data in various grid forms is consistent with the spatial resolution of the digital elevation model.

[0014] The small watershed is the watershed corresponding to the smallest level river in Horton's law. Based on the digital elevation model, the target watershed is divided into I small watersheds B1, B2, ... B i ,…B I , and statistics on the area, terrain elevation difference, average slope, channel length, channel width and channel slope of each small watershed.

[0015] In some embodiments, in step S2,

[0016] For gravity erosion, T is identified through multi-period orthophotos of the watershed. j The newly added collapse and landslide area during the period is counted based on the collapse and landslide area. j Time period small watershed Bi The total volume of materials released by the collapse and landslide within the j Time period small watershed B i Gravity erosion (E G ) ij , T j It is a time unit determined according to the sediment estimation requirements, and the duration of each period ΔT is the same;

[0017] For debris flow erosion, first obtain the small watershed B according to rainfall data. i In period T j All effective rainfall event information in the data set, including the rainfall duration and average rainfall intensity of each effective rainfall event, is used to determine whether each effective rainfall event triggers a debris flow through the rainfall threshold trigger condition; when it is determined that an effective rainfall event does not trigger a debris flow, the volume of the outflow of the effective rainfall event is 0; when it is determined that an effective rainfall event triggers a debris flow, the volume of the outflow of the effective rainfall event is calculated; statistics T j Time period small watershed B i The total volume of debris flow outflow is taken as T j Time period small watershed B i The amount of debris flow erosion (E D ) ij ;

[0018] For channel erosion, T j Time period small watershed B i The channel in the channel is divided into several channel segments, and the channel erosion rate of each channel segment is calculated respectively. Based on the channel erosion rate, T is calculated. j Time period small watershed B i The amount of channel erosion (E g ) ij ;

[0019] For slope erosion, the modified universal soil loss equation RUSLE is used to calculate the T of each grid. j The soil erosion modulus within the time period is then multiplied by the grid area to obtain the grid scale T j The amount of soil erosion in the period; the amount of soil erosion in the small watershed B i The soil erosion amount of each grid within the range is accumulated to obtain T j Time period small watershed B i The amount of slope erosion (E S ) ij ;

[0020] Sum the four types of erosion to get T j Small watershed B during the period i Total erosion (E) ij .

[0021] In some embodiments, T is calculated according to the following formula: j Time period small watershed B i Gravity erosion (E G ) ij :

[0022]

[0023] Where, ρ G is the density of the collapse and landslide material; (V G ) k T j Time period small watershed B i The volume of material released by the kth collapse and landslide in T j Time period small watershed B i The total number of internal collapse and landslides; the volume of material released by a single collapse and landslide V G Calculate according to the following formula:

[0024]

[0025] Where A G is the area of ​​a single collapse landslide; α and γ are coefficients, α is 0.05±0.02, γ is 1.1~1.3 for soil landslide, and γ is 1.3~1.6 for rock landslide;

[0026] The small watershed B i In period T j All valid rainfall events in the data are obtained by following the steps below:

[0027] First, the rainfall data after spatial division is calculated according to the following formula: τ Average rainfall in:

[0028]

[0029] Where, Small watershed B i In time period t τ Average rainfall in t τ is the temporal resolution of rainfall data, M is the temporal resolution of the small watershed B i The total number of grids within Small watershed B i The mth grid in the time period t τ of rainfall;

[0030] Small watershed B i In time period t τ Average rainfall Divide by time period t τ As a small watershed B i In time period tτ Average rainfall intensity;

[0031] Traverse each time period T j Obtain the rainfall intensity time series matrix of each small watershed, and determine the rainfall intensity of each small watershed in each period T in chronological order. j When the rainfall intensity is greater than the first set value, it is considered that a valid rainfall event has started. When the rainfall intensity is less than the first set value and continues for not less than the second set value, it is considered that the valid rainfall event has stopped. The period of time when the rainfall intensity is continuously greater than the first set value is considered as a valid rainfall event, and the rainfall duration D and average rainfall intensity of the valid rainfall event are recorded. Thus, we can obtain the small watershed B i In period T j All valid rainfall events information within;

[0032] The rainfall threshold trigger condition is used to determine whether each effective rainfall event triggers a debris flow, specifically:

[0033] Assume that the rainfall threshold is I c , according to the following formula with small watershed as the unit:

[0034] I c =α D D -β

[0035] Where, α D and β are both constants;

[0036] When the average rainfall intensity of an effective rainfall event When , it is considered that no debris flow is triggered;

[0037] When the average rainfall intensity of an effective rainfall event When the debris flow is triggered, the statistics of small watershed B i In T j Rainfall data for each event that will trigger a debris flow during the time period Where l is the number of rainfall events that will trigger debris flow, the total number is L events, D l and Small watershed B i In T j The duration and average rainfall intensity of the first rainfall event that will trigger a debris flow within the time period are used to calculate the volume of debris flow discharge V of each event using the following formula: D :

[0038]

[0039] Where Q D is the peak flow rate of debris flow; γ Dis the bulk density of debris flow; γ W is the bulk density of clean water; S is the bulk density of solid matter in debris flow; Q P is the storm flood flow; K P is the confluence coefficient; F i Small watershed B i The drainage area; D C is the congestion coefficient; T is the duration of a debris flow; L D is the length of the main ditch of debris flow; U D is the speed of debris flow; S is the slope of gully bed;

[0040] The T j Time period small watershed B i The amount of debris flow erosion (E D ) ij Calculate according to the following formula:

[0041]

[0042] Where, ρ D is the density of debris flow outflow material; (V D ) l T j Time period small watershed B i The volume of debris discharged from the first debris flow;

[0043] The T j Time period small watershed B i The amount of channel erosion (E g ) ij Calculate according to the following formula:

[0044] (E g ) ij =(G g ) ij ΔT

[0045]

[0046] Where, L s is the length of the s-th channel; r s is the annual average erosion rate of the slope of the channel section, which is taken as the annual average change rate of the cross section of the channel section; ρ is the density of eroded sediment; ΔT is T j the duration of the session;

[0047] The T j Small watershed B during the period i The amount of slope erosion (E S ) ij Calculate according to the following formula:

[0048]

[0049] Where A g is the area of ​​a single grid; A m Small watershed B i Soil erosion modulus of the mth grid within the range; M is the soil erosion modulus of the small watershed B i The total number of grid cells within.

[0050] In some embodiments, in step S3,

[0051] Regarding the sand production and sedimentation caused by gravity erosion, if the collapse and landslide location is not connected to the river system, the sand production and sedimentation caused by gravity erosion caused by the collapse and landslide are both 0. If the collapse and landslide location is connected to the river system, the T j Time period small watershed B i Sedimentation 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] Where, (E G ) ij T j Time period small watershed B i The amount of gravity erosion; p and P are T j Time period small watershed B i Number and total number of collapse and landslides connected to the river system; G The mass of material input to the river for a single landslide; w G is the average distance that a single landslide extends from the river bank into the water, based on historical remote sensing images or field surveys; L G is the length of the river section affected by a single collapse and landslide; k G is the correction coefficient; ρ is the density of eroded sediment; h is L G The average water depth of the corresponding river section; Q is the flow rate of the main river at the location of a single collapse and landslide; c and f are coefficients; T G ′ is T jTime period small watershed B i The amount of sediment produced corresponding to the amount of gravity erosion;

[0057] Regarding the sand production and deposition caused by debris flow erosion, first calculate T according to the following formula: j Time period small watershed B i Sediment transport ratio (SDR) of internal debris flow erosion D ) ij :

[0058]

[0059] Where θ is T j Time period small watershed B i The angle at which the main ditch enters the main river; γ m and γ D T j Time period small watershed B i The bulk density of the main river and debris flow; q m and q D T j Time period small watershed B i The unit-width flow of the main river and debris flow is obtained based on the hydrological data, and the unit-width flow of the debris flow is calculated as q D =Q D / w D , w D T j Time period small watershed B i The width of the debris flow channel, Q D T j Time period small watershed B i Peak debris flow discharge;

[0060] Then based on the sediment delivery ratio (SDR D ) ij Calculate T j Time period small watershed B i Sediment yield and sedimentation caused by debris flow erosion:

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

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

[0063] Where, (T D) ij T j Time period small watershed B i The amount of sediment produced by debris flow erosion (D D ) ij T j Time period small watershed B i the amount of sediment eroded by debris flows;

[0064] For the sediment production and deposition of gully erosion and slope erosion, the T is first calculated based on the grid-scale sediment connectivity index in each small watershed. j Time period small watershed B i Sediment transport ratio (SDR) of gully erosion or slope erosion IC ) ij :

[0065]

[0066] Where, (SDR max ) ij It's T j Time period small watershed B i The theoretical maximum sediment transport ratio is related to the surface soil texture; IC ij T j Time period small watershed B i The average sediment connectivity index is taken as T j Time period small watershed B i The mean value of the sediment connectivity index at each grid scale; IC0 and k are the correction coefficients for calculating the sediment transport ratio;

[0067] Then based on the sediment delivery ratio (SDR IC ) ij Calculate T j Time period small watershed B i The sediment yield and deposition corresponding to the gully erosion, and the sediment yield and deposition corresponding to the 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] Where, (E g ) ij T j Time period small watershed B i The amount of channel erosion, (T g ) ij and (D g ) ij T j Time period small watershed B i The amount of sediment production and deposition corresponding to the amount of gully erosion; (E S ) ij T j Time period small watershed B i The amount of slope erosion, (T S ) ij and (D S ) ij T j Time period small watershed B i The amount of sediment production and deposition corresponding to the amount of slope erosion.

[0073] In some embodiments, the grid-scale sediment connectivity index within a small watershed is denoted as IC and is calculated as follows:

[0074]

[0075] IS m =RI m +C·P

[0076]

[0077] Where D up is the upslope component of a small watershed, reflecting the sediment production potential of the upstream; is the average impedance factor of the upslope catchment area of ​​a small watershed, representing the resistance of surface roughness to the flow of water and sediment; is the average slope of the upslope catchment area of ​​a small watershed; A up is the upslope catchment area of ​​a small watershed; D dn is the downslope component of a small watershed, reflecting the path resistance of sediment to the target; d mis the length of the flow path of the mth grid in a small watershed along the steepest downslope direction; W m is the impedance factor of the mth grid in a small watershed; SS m IS is the slope gradient of the mth grid in a small watershed; max IS is the maximum surface index of the small watershed where the grid is located; m is the surface index of the mth grid in a small watershed; RI m is the roughness index of the mth grid in a small watershed; To calculate RI m Used in Grid moving scanning pane, x m is the elevation of a grid, x s For the surrounding of a certain grille is the average elevation of the grid; 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] According to the distribution of slope, river width and river type along the river, the river in the target basin is divided into X river sections R1, R2, ... R x ,…R X , stipulating that each river section shall have at most one reservoir or lake, and that the reservoir or lake shall be located at the entrance of the river section;

[0080] Calculate the suspended sediment load of the river in the target basin section by section. j Any river section R within the time period x The amount of suspended sediment output (SS out ) xj for:

[0081]

[0082] Where, (SS in ) xj T j River section R x The amount of suspended sediment input from upstream to the main river; (I T ) n For river section R x The amount of suspended sediment input from the nth tributary into the main river, n and N are the x The number and total number of internal tributaries, then Indicates T j Period River Section R x The amount of suspended sediment input from all tributaries into the main river is xThe amount of suspended sediment IT inputted into the main river by a certain tributary is calculated based on the sediment yield of the small watershed obtained in step S3; (E B ) xj T j Period River Section R x The particle size of the riverbank erosion is consistent with the mass of the suspended sediment, which is calculated based on the water flow work; (O F ) xj T j Period River Section R x The amount of suspended sediment deposited on the floodplain is based on T j Period River Section R x The average flow rate through the floodplain, the average settling velocity of suspended sediment and the average area of ​​the floodplain are calculated; (O D ) xj T j Period River Section R x The amount of suspended sediment transported in irrigation or water diversion projects is based on T j Period River Section R x The average output flow and the average sediment content of the output water in the irrigation or water diversion project are calculated; (O R ) xj T j Period River Section R x The amount of suspended sediment deposition in reservoirs or lakes is obtained based on hydrological sediment observation data, or based on T j River section R x The amount of suspended sediment (SS in ) xj It is calculated based on the average sediment retention rate of the reservoir or lake.

[0083] In some embodiments, the amount of suspended sediment input from a tributary into the main river in a single river section 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] Where, T G ′ is T j Time period small watershed B i The amount of sediment produced corresponds to the amount of gravity erosion; T Dis the sediment yield corresponding to the debris flow erosion of a small watershed corresponding to a tributary in a single river reach; T g is the sediment yield corresponding to the channel erosion of a small watershed corresponding to a tributary in a single river reach; T S is the sediment yield corresponding to the slope erosion of a small watershed corresponding to a tributary in a single river reach; (Δ s ) G 、(Δ s ) D 、(Δ s ) g T G ′、T D and T g The proportion of suspended sediment in the medium load is obtained by extracting the characteristic particle size proportion of suspended sediment in the target watershed from the gradation curves of collapse and landslide deposits, debris flow fan and channel slope materials;

[0086] Calculate T according to the following formula j Period River Section R x The particle size of the riverbank erosion is consistent with the mass of the 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] Where b is the adjustment parameter; the variable with subscript x represents the river section R x The average value, the subscript j represents the number of the time period; ρ w is the density of pure water; g is the acceleration due to gravity; Q B is the flow rate on the flat land of the river section; S is the slope of the river section; h B is the river bank height; L B is the length of the river section; ρ B is the density of the shore material; (Δ s ) B is the proportion of suspended sediment in the shore material;

[0089] Calculate T according to the following formula j Period River Section R x The amount of suspended sediment deposited on the floodplain (OF ) xj :

[0090]

[0091] Where, (O f ) xj T j Period River Section R x The average flow of inland flow through the floodplain, that is, T j The average value of peak flow exceeding amortized flow in all floods during the period when peak flow is greater than flat flow; v xj T j Period River Section R x Average settling velocity of suspended sediment; (A f ) xj T j Period River Section R x Average floodplain area within the

[0092] Calculate T according to the following formula j Period River Section R x The amount of suspended sediment transported in irrigation or water diversion projects (O D ) xj :

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

[0094] Where, (Q D ) xj T j Period River Section R x The average output flow in irrigation or water diversion projects, (C D ) xj T j Period River Section R x Average sediment content of output water from irrigation or water diversion projects;

[0095] In the case where there is no hydrological sediment observation data at the inlet or outlet of a reservoir or lake, T is calculated according to the following formula: j Period River Section R x The amount of suspended sediment in the reservoir or lake (O R ) xj :

[0096] (Q R ) xj =(SS in ) xj ·TExj

[0097]

[0098] In the formula, TE xj T j Period River Section R x The average sediment retention rate of the reservoir or lake; C R is the effective storage capacity of the reservoir or lake; I R It is the average multi-year runoff of a reservoir or lake.

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

[0100] A basic data acquisition module is configured to collect basic data of the target watershed, including rainfall, soil, vegetation, topography, and hydrological data, organize the various basic data into a grid format and perform unified spatial registration, set the boundaries of the small watershed as the spatial unit for sediment estimation, spatially divide the various basic data based on the small watershed boundaries, and divide the various basic data at the small watershed scale into time periods based on the time scale requirements of the 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 temporal and spatial distribution of each type of erosion and the total erosion in the target watershed;

[0102] The sediment yield and deposition calculation module is configured to calculate the sediment yield and deposition corresponding to various types of erosion at the small watershed scale. For gravity erosion, the sediment yield is calculated based on the volume of river material input from collapses and landslides connected to the water system, and the sediment deposition at the small watershed scale is obtained by subtracting the sediment yield from the gravity erosion. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is first calculated, and then the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. The small watershed-scale sediment transport ratio 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 small watershed-scale sediment transport ratio for gully erosion and slope erosion is calculated based on the grid-scale sediment connectivity index within each small watershed. The spatiotemporal distribution of sediment yield and deposition in the target watershed is obtained based on the sediment yield and deposition of various types of erosion at the small watershed scale.

[0103] The suspended sediment transport calculation module is configured to calculate the suspended sediment transport of small basins in the main river system section by section based on the sediment yield of all small basins in the target basin in each time period, according to the upstream and downstream relationship of the locations where each small basin in the target basin flows into the river, and combine 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, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the basin sediment estimation method according to any embodiment of the first aspect of the present invention.

[0105] The beneficial effects of the present invention are:

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

[0107] 2. Correlate the physical processes of erosion, sediment production, and deposition at the small watershed scale, and at the river system scale, correlate the physical processes of sediment production in the small watershed and sediment transport in the main river. This allows for a quantitative description of the number of erosion, sediment production, and sediment transport processes throughout the target watershed, and provides a temporal and spatial distribution within the target watershed. This allows for the rapid and precise location of the main erosion areas and sediment source areas within the watershed.

[0108] 3. The method system mainly relies on satellite images and hydrological data, has low requirements for on-site measurement and sampling, is easy to control the cost, quickly build models, and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Figure 1 This is an overall flow chart of a method for estimating sediment in a watershed provided by an embodiment of the first aspect of the present invention;

[0110] Figure 2 Schematic diagram of small watershed erosion and sediment transport involved in the embodiment of the first aspect of the present invention;

[0111] Figure 3 It is a schematic diagram of a calculation process of suspended load transport in a river section in a basin sediment estimation method provided by an embodiment of the first aspect of the present invention;

[0112] Figure 4 It is a structural diagram of an electronic device provided by an embodiment of the third aspect of the present invention. DETAILED DESCRIPTION

[0113] In order to make the purpose, technical solutions and advantages of this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0114] On the contrary, this application covers any alternatives, modifications, equivalents, and solutions made within the spirit and scope of this application as defined by the claims. Furthermore, to facilitate a better understanding of this application, certain specific details are described in detail below in the detailed description of this application. Those skilled in the art will be able to fully understand this application without these details.

[0115] See also Figure 1 、 Figure 2 The first embodiment of the present invention provides a method for estimating sediment in a watershed, comprising the following steps:

[0116] Step S1: Collect basic data of the target watershed, including rainfall, soil, vegetation, topography, and hydrological data. Organize the basic data into a grid format and perform unified spatial registration. Set the boundaries of the small watershed as the spatial unit for sediment estimation. Based on the boundaries of the small watershed, perform spatial division of the basic data. Based on the time scale requirements of the sediment estimation, divide the basic data of the small watershed 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, and obtain the spatiotemporal distribution of each type of erosion amount and the total erosion amount in the target watershed;

[0118] Step S3: For gravity erosion, the sediment yield is calculated based on the volume of river material input from landslides and collapses connected to the water system, and the sediment yield is subtracted from the gravity erosion volume to obtain the sedimentation volume 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. Then, the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. The small watershed-scale sediment transport ratio 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 small watershed-scale sediment transport ratios for gully erosion and slope erosion are calculated based on the grid-scale sediment connectivity index within each small watershed.

[0120] The temporal and spatial distribution of sediment yield and sedimentation in the target watershed is obtained based on the sediment yield and sedimentation of various erosion factors at the small watershed scale;

[0121] Step S4: Based on the sediment yield of all small watersheds in the target watershed calculated in step S3 during each time period, the suspended sediment transport of the small watersheds in the main river system is calculated section by section according to the upstream and downstream relationship of the locations where each small watershed in the target watershed flows into the river. The distribution of the suspended sediment transport along the flow direction of the main river system is obtained by combining dredging, reservoir siltation, and the input and output of suspended sediment in the river section.

[0122] In some embodiments, step S1 is to collect and pre-process basic data of the target watershed, specifically including:

[0123] Step S11: basic data collection.

[0124] Collect basic data such as rainfall, soil, vegetation, topography, and orthophotos for the target watershed. Rainfall data is raster data with a temporal resolution of 3 hours or higher; soil data primarily includes the organic matter content of sand, silt, and clay in the surface soil, and is raster data; vegetation data is raster data, including the Normalized Difference Vegetation Index (NDVI) and vegetation types (trees, shrubs, etc.); topographic data uses a digital elevation model (DEM) with a spatial resolution of at least 30 meters; in addition, basic data also includes land use types, which are used to calculate dimensionless soil and water conservation measures. All of these basic data are spatially aligned, and the spatial resolution is unified to match that of the DEM. Orthophotos of the target area must be collected from multiple periods, with consistent spatial resolution and unified spatial alignment.

[0125] Collect hydrological data for the target basin, including river system data within the target basin (this river system data can be extracted using a DEM or pre-extracted river system data for the target basin), flow, runoff, and sediment transport information from hydrological stations, with a temporal resolution as low as daily. If there are no hydrological stations within the target basin, find water and sediment data from the nearest hydrological station downstream. If hydrological data such as flow and depth are available for the target area, or data obtained from distributed hydrological model simulations, collect these data as well.

[0126] Step S12: basic data preprocessing.

[0127] Spatial scale division: The basin corresponding to the smallest level river in Horton's law is set as a small basin, which is used as the spatial unit for sediment estimation. Based on the DEM, the target basin is divided into I small basins B1, B2, ... B i ,…B I , and statistics were collected on the area, terrain elevation difference, average slope, channel length, channel width and channel slope of each small watershed.

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

[0129] Preprocessing of rainfall data: First, use GIS analysis tools to obtain the rainfall data of each small watershed B. iThe vector data file of the range is used to establish the mapping relationship between the small watershed and the raster rainfall data, and the spatial weighted average method is used to calculate the B i In each time period t τ The average rainfall in the area is calculated as follows:

[0130]

[0131] Where, Small watershed B i In time period t τ The average rainfall, t τ is the temporal resolution of rainfall data, usually 1h or 3h, and M is the B of the small watershed. i The total number of grids in A g is the area of ​​a single grid, Small watershed B i The mth grid in the time period t τ of rainfall.

[0132] Small watershed B i In time period t τ The average rainfall divided by t τ It is the average rainfall intensity of the small watershed during this period. j Obtain the rainfall intensity time series matrix of each small watershed, and determine the rainfall intensity of each small watershed in each period T in chronological order. j When the rainfall intensity is greater than 1 mm / h, it is considered that an effective rainfall begins. When the rainfall intensity is less than 1 mm / h and continues for at least 6 hours, it is considered that the effective rainfall stops. The period of time when the rainfall intensity is continuously greater than 1 mm / h is considered as an effective rainfall, and its rainfall duration D (unit: h) and average rainfall intensity are recorded. (Unit: mm / h) and other indicators to obtain small watershed B i In period T j All valid rainfall events information within.

[0133] In some embodiments, step S2 is to calculate the erosion amount at the small watershed scale according to different erosion types, and calculate T j The watershed erosion during the period is divided into four categories: gravity erosion, debris flow erosion, gully erosion and slope erosion. Figure 2 , the calculation process of each type of erosion amount is described as follows:

[0134] Step S21: Gravity erosion amount

[0135] Gravity erosion is mainly caused by collapse and landslides in the basin. The T jThe area of ​​new collapse and landslides during the period is then used to estimate the volume of material released by the collapse and landslides during the period based on the relationship between the area and volume of the collapse and landslides. For a single collapse and landslide, the volume of material released is calculated as:

[0136]

[0137] Where V G A is the volume of material released by a single collapse landslide, G is the area of ​​a single collapse landslide, α and γ are coefficients, α is generally taken as 0.05±0.02, γ is taken as 1.1~1.3 for soil landslide, and γ is taken as 1.3~1.6 for rock landslide.

[0138] Statistics T j Time period small watershed B i The total volume of materials released by the collapse and landslide within the G ) ij :

[0139]

[0140] Where, ρ G The density of the collapse and landslide material is generally 2.0 to 2.5 t / m 3 For soil landslide, the value is generally 1.6~2.3t / m 3 ; K is T j Time period small watershed B i The total number of collapses and landslides; k is T j Time period small watershed B i Number of internal collapse and landslide materials, (V G ) k T j Time period small watershed B i The volume of material released by the kth collapse and landslide.

[0141] Step S22: Debris flow erosion amount

[0142] The debris flow process strongly transports the material source in the small watershed, causing the channel to cut down and transporting a large amount of material to the gully mouth accumulation fan. Calculating the volume of debris flow outflow can approximate the amount of debris flow erosion in the small watershed. Since debris flow gullies are often narrow and deep, it is difficult to directly determine whether they have occurred through remote sensing images, and the time and cost of on-site investigation is too high. Considering that most debris flows are triggered by rainfall, the rainfall threshold trigger condition is used to determine whether a debris flow has occurred. The rainfall threshold is set to I c , calculated based on formula (4) with small watershed as the unit:

[0143] I c =α D D -β (4)

[0144] Where D is the duration of an effective rainfall event in the small watershed (h), α D and β are constants. For the Wenchuan earthquake area, α can be taken as D =66.36, β=-0.79.

[0145] Based on the set rainfall threshold I c Judge T j Time period small watershed B i Whether each effective rainfall event triggers a debris flow:

[0146] like It is considered that no debris flow is triggered and the volume of the discharged material is 0.

[0147] like It is considered that debris flow is triggered, and the statistics of small watershed B i In T j Rainfall data for each event that can trigger debris flow during the time period Where l is the number of rainfall events that can trigger debris flow, the total number is L events, D l and Small watershed B i In T j The duration and average rainfall intensity of the first rainfall event that can trigger a debris flow within the time period are used to calculate the volume V of the debris flow discharge using equations (5) to (9): D :

[0148]

[0149] Where Q D is the peak flow rate of debris flow (unit: m 3 / s); the coefficient 19 / 72 in formula (5) is the empirical coefficient given by the "Design Code for Investigation and Prevention of Debris Flows in Hydropower Projects" (NB / T 10139-2019); γ D is the bulk density of debris flow, which is determined through on-site investigation or regional debris flow characteristics; γ W γ is the clear water density. Generally, except for extremely strong sediment transport under extreme conditions, the main river density is unlikely to change significantly compared with the clear water density. Therefore, the main river density can be approximately determined by the clear water density, and the debris flow density can be determined by the regional debris flow density. S is the bulk density of solid matter in debris flow; Q P is the storm flood flow; K P is the confluence coefficient, and K is generally used for steep slopes in mountainous areas. P =0.7~0.9 (weak surface permeability, fast convergence speed), K is generally used in hilly areas P = 0.5~0.7 (medium infiltration and confluence conditions), plain or vegetation covered area KP =0.3~0.5 (strong penetration, slow convergence speed); F i Small watershed B i The drainage area; D C is the congestion coefficient, which can be obtained by referring to the Code for Calculation of Floods in Design of Water Conservancy and Hydropower Projects (Ministry of Water Resources of the People's Republic of China, 2006) (SL44-2006) in combination with on-site inspection; T is the duration of the debris flow (unit: s); L D is the length of the main ditch of debris flow; U D is the speed of debris flow; S is the slope of the gully bed.

[0150] Finally, statistics T j Time period small watershed B i The total volume of debris flow outflow is taken as T j Time period small watershed B i The amount of debris flow erosion (E D ) ij :

[0151]

[0152] Where, ρ D is the density of debris flow discharge, which is 1.3-1.8t / m for the area dominated by rare debris flow. 3 , in the area dominated by viscous debris flow, the rate is 2.0~2.4t / m 3 , the transitional debris flow dominant area takes 1.8~2.0t / m 3 ;(V D ) l T j Time period small watershed B i The volume of discharge from the first debris flow.

[0153] Step S23: Channel erosion amount

[0154] Gully erosion refers to the erosion of the gully caused by the flow of rainfall, including downcutting, lateral erosion and upstream erosion. j Time period small watershed B i , calculate the channel erosion rate (G g ) ij (t / y) is:

[0155]

[0156] In the formula, (G g ) ij T j Time period small watershed B i Channel erosion rate; L s is the length of the s-th channel, r sis the average annual erosion rate of the slope in the channel section (m 2 / y), which is the average annual change rate of the cross section of the channel section; ρ is the density of eroded sediment, which is generally taken as 1.6t / m 3 .

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

[0158] For the channel segments in a stable period (such as mountain torrent channels, debris flow channels, etc., and no major collapse, landslide and debris flow events occurred within the time range of concern), the annual average erosion rate of the channel segment slope is r s The value can be approximated as a constant, that is, whether obtaining the annual average erosion rate of the channel section slope through DEM or on-site monitoring, only data with a shorter time span is needed.

[0159] Calculate T according to the following formula j Time period small watershed B i The amount of channel erosion (E g ) ij :

[0160] (E g ) ij =(G g ) ij ·ΔT (12)

[0161] Step S24: Slope erosion amount

[0162] The slope erosion of the target watershed is calculated by using the modified universal soil loss equation (RUSLE) to calculate the T of each grid. j The soil erosion modulus within the time period is then multiplied by the grid area to obtain the grid scale T j Soil erosion amount in a certain period. i The soil erosion amount of each grid within the range is accumulated to obtain the slope erosion amount of the small watershed (E S ) ij . Specifically:

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

[0164] A=R·S·L·K·C·P (13)

[0165] Where A is the soil erosion modulus (t / (km 2 ·y); R is the rainfall erosivity factor (MJ / (km 2·y), calculated based on rainfall data; L and S are dimensionless terrain factors, L is the slope length factor, and S is the slope factor, both of which 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; and P is the dimensionless soil and water conservation measure factor, assigned according to slope gradient and land use type.

[0166] Calculate T according to the following formula j Small watershed B during the period i The amount of slope erosion (E S ) ij :

[0167]

[0168] Where A g is the area of ​​a single grid, A m Small watershed B i The soil erosion modulus of the mth grid within the range, M is B i The total number of grids within the small watershed.

[0169] Step S25: Total erosion amount and basin erosion distribution

[0170] T j Small watershed B during the period i Total erosion (E) ij is the sum of the above four erosion amounts, that is:

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

[0172] This also yielded T j The spatial distribution of total erosion, gravity erosion, channel erosion and slope erosion in the watershed within a period of time is calculated based on the small watershed. The above calculations are performed for different time periods to obtain the spatiotemporal distribution of various erosion amounts and total erosion in the target watershed.

[0173] The target basin is in T j The total erosion during the period is:

[0174]

[0175] This can be used to obtain the change of total erosion in the target area over time.

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

[0177] In some embodiments, step S3 calculates the sediment yield in 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 as follows:

[0178] Step S31: Sand production and deposition due to gravity erosion

[0179] First, calculate the mass of landslides entering the river. Two situations are considered here: First, if the landslide location is not connected to the river system, the gravity erosion caused by the landslide will not be converted into sediment that can be transported by the water flow. Subsequently, channel erosion and slope erosion will continue to occur. These will be calculated in the subsequent channel and slope erosion sections and do not need to be calculated again here. Second, if the landslide location is connected to the river system, the portion of the single landslide material entering the river is calculated according to the following formula:

[0180] T G =k G ·ρ·w G ·L G ·h (17)

[0181] h=cQ f (18)

[0182] Where, T G The mass of material input to the river for a single landslide; w G is the average distance that the landslide extends from the river bank to the water, L G is the length of the river section affected by the collapse and landslide. Both parameters can be obtained by extracting multiple satellite images of the landslide area; k G is the correction coefficient, which is generally 0.7-0.8; ρ is the density of eroded sediment; h is the difference between the main river and L G The average water depth of the corresponding river section; Q is the flow of the main river at the collapse and landslide location, obtained through hydrological data; c and f are coefficients, generally c = 0.25 ~ 0.55, f = 0.3 ~ 0.4.

[0183] Then T j Time period small watershed B i Sedimentation amount due to internal gravity erosion (D G ) ij for:

[0184]

[0185] Where, T G ′ is T j Time period small watershed B i The sediment yield corresponding to the gravity erosion; p and P are T j Time period small watershed B i The numbers and total number of collapses and landslides connected to the river system.

[0186] Step S32: Sand production and deposition caused by debris flow erosion

[0187] First calculate T j Time period small watershed B i The sediment transport ratio of internal debris flow erosion refers to the ratio of sediment carried by the river to the volume of debris flow outflow, which is calculated by the following formula:

[0188]

[0189] Where, (SDR D ) ij T j Time period small watershed B i The sediment transport ratio of internal debris flow erosion; θ is T j Time period small watershed B i The angle at which the main ditch flows into the main river is obtained through the river system data in the target basin; γ m and γ D T j Time period small watershed B i The bulk density of the main river and debris flow. The bulk density of the main river changes little with different periods and small watersheds and is generally taken as a constant value; q m and q D T j Time period small watershed B i The unit-width flow of the main river and debris flow is obtained based on the hydrological data, and the unit-width flow of the debris flow is calculated as q D =Q D / W D , W D T j Time period small watershed B i The width of the debris flow channel, Q D T j Time period small watershed B i Peak flow rate of debris flow.

[0190] Then, T is calculated based on the above sediment transport ratio. j Time period small watershed B i The sediment yield corresponding to the debris flow erosion (T D )ij and sedimentation (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: Sand production and deposition from gully erosion and slope erosion

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

[0195]

[0196] Where IC is the grid-scale sediment connectivity index within a small watershed. A larger value indicates higher sediment connectivity. up is the upslope component of a small watershed, reflecting the sediment production potential of the upstream; is the average impedance factor of the upslope catchment area of ​​a small watershed, representing the resistance of surface roughness to the flow of water and sediment; is the average slope of the upslope catchment area of ​​a small watershed (m / m); A up is the upslope catchment area of ​​a small watershed (m 2 );D dn is the downslope component of a small watershed, reflecting the path resistance of sediment to the target; d m is the length of the flow path along the steepest downslope direction of the mth grid in a small watershed (m); W m is the impedance factor (local surface roughness) of the mth grid in a small watershed; SS m is the slope gradient of the mth grid in a small watershed (m / m).

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

[0198]

[0199] Where IS maxis the maximum surface index of the small watershed where the grid is located; the surface index IS of each grid m Calculated as:

[0200] IS m =RI m +C·P (27)

[0201] Roughness index RI of the mth grid m Calculated as:

[0202]

[0203] Where, Used in calculations Grid moving scanning pane, x m is the elevation of a grid, x s For the surrounding of a certain grille The vegetation factors C and P are the same as the C and P factors calculated in the RUSLE method when calculating slope erosion (Equation 13).

[0204] Step S332: Calculate sediment transport ratio

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

[0206] For T j During this period, the sediment connectivity index IC was used to calculate the B i Sediment transport ratio of gully erosion or slope erosion:

[0207]

[0208] Where, (SDR IC ) ij It's T j Time period small watershed B i Sediment transport ratio of gully erosion or slope erosion; (SDR max ) ij It's T j Time period small watershed B i Theoretically, the maximum sediment transport ratio that can occur is related to the texture of the surface soil and can generally be taken as 1; IC ij T j Time period small watershed B i The average sediment connectivity index is taken as T j Time period small watershed B i The mean value of the sediment connectivity index at each grid scale within the grid; IC0 and k are correction coefficients for calculating the sediment transport ratio and need to be calibrated. ij =IC0, there is (SDRIC ) ij =0.5(SDR max ) ij , therefore, IC0 is (SDR max ) ij The sediment connectivity index value corresponding to half of the value is generally taken as (SDR max ) ij =1, then IC0 is (SDR max ) ij =0.5, which needs to be determined by trial calculation; l is generally greater than 0, so you can first take a value between k=1 and 2, substitute it in, and then determine the specific value by trial calculation. The trial calculation should be stopped if the calculated result is consistent with some sediment yield observation data at the outlet of the small watershed.

[0209] Step S333: Calculate sand production and deposition

[0210] Calculate T based on the above sediment transport ratio j Time period small watershed B i The amount of channel erosion (E g ) ij The corresponding sediment yield (T g ) ij and sedimentation (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 Time period small watershed B i The amount of slope erosion (E S ) ij The corresponding sediment yield (T S ) ij and sedimentation (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 yielded T j The spatial distribution of sediment yield and deposition corresponding to gravity erosion, debris flow erosion, gully erosion and slope erosion in the watershed within a period of time is calculated by performing the above calculations for different time periods to obtain the spatiotemporal distribution of various types of sediment yield and deposition in the target watershed.

[0217] It can be understood that step S3 quantifies the sediment yield and deposition corresponding to various erosion types in small watersheds, and obtains the spatiotemporal distribution characteristics of the sediment yield and deposition in the target watershed, thereby realizing the precise positioning of the sediment source in the watershed.

[0218] In some embodiments, step S4 is to calculate the amount of river sediment transport. After calculating the erosion, sediment yield, and deposition of all small watersheds in the target basin in each period, the sediment transport in the main river system is calculated section by section according to the upstream and downstream relationship of the location where the small watersheds flow into the river. Considering that the coarse bed load has a limited transport distance in the river system, step S4 mainly calculates the sediment transport for the finer suspended load, see Figure 3 , specifically including the following steps:

[0219] According to the distribution of slope, river width and river type along the river, the river in the target basin is divided into X river sections R1, R2, ... R x ,…R X The slope, river width and river shape in each river section do not change significantly. There is at most one reservoir or lake in each river section, and the reservoir or lake is located at the entrance of the river section.

[0220] Calculate the suspended sediment load of the river in the target basin section by section. j Any river section R in the period x The amount of suspended sediment output (SS out ) xj for:

[0221]

[0222] Where, (SS in ) xj T j River section R x The amount of suspended sediment input from upstream to the main river; (IT ) n For river section R x The amount of suspended sediment input from the nth tributary into the main river, n and N are the x The number and total number of internal tributaries, then Indicates T j Period River Section R x The amount of suspended sediment input into the main river by all tributaries within the river; (E B ) xj T j Period River Section R x The particle size of the riverbank erosion is consistent with the mass of the suspended sediment; (O F ) xj T j Period River Section R x The amount of suspended sediment deposited on the floodplain; (O M ) xj T j Period River Section R x The amount of artificial dredging shall be determined according to the actual scale of dredging in the river; (O D ) xj T j Period River Section R x The amount of suspended sediment transported in irrigation or water diversion projects; (O R ) xj T j Period River Section R x The amount of suspended sediment deposited in a reservoir or lake.

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

[0224] Among them, combined with the calculation of sediment yield of small watersheds in step S3, the amount of suspended sediment input from a tributary into the main river in a single river section is I T Calculated as:

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

[0226] Where, T G′ is the sediment yield corresponding to the gravity erosion of a small watershed corresponding to a tributary in a single river reach, which is taken as the sum of the mass of materials input into the river by all collapses and landslides connected to the river system in a small watershed; T D is the sediment yield corresponding to the debris flow erosion of a small watershed corresponding to a tributary in a single river reach; T g is the sediment yield corresponding to the channel erosion of a small watershed corresponding to a tributary in a single river reach; T S is the sediment yield corresponding to the slope erosion of a small watershed corresponding to a tributary in a single river reach; (Δ s ) G 、(Δ s ) D 、(Δ s ) g T G ′、T D and T g The proportion of suspended sediment is obtained by extracting the proportion of characteristic particle size (e.g. 0.05 mm) of suspended sediment in the target watershed from the gradation curves of collapse and landslide deposits, debris flow fans and channel slope materials.

[0227] T j Period River Section R x The particle size of the riverbank erosion is consistent with the mass of the suspended sediment (E B ) xj The calculation based on water flow work is:

[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] Where b is the adjustment parameter used to adjust the calculation results to suit the actual situation; the variable with the subscript x represents the river section R x The average value, the subscript j represents the number of the time period; ρ w is the density of pure water; g is the acceleration due to gravity; Q B is the flow rate on the flat land of the river section. In the absence of measured data, the flood flow rate with a return period of 1 to 2 years can be used as an approximation; S is the slope of the river section, ρ w g(Q B ) xj S xj That is Tj Period River Section R x The water flow work; h B is the river bank height, L B is the length of the river section, ρ B is the density of the shore material, (Δ s ) B It is the proportion of suspended sediment in the shore material.

[0230] T j Period River Section R x The amount of suspended sediment deposited on the floodplain (O F ) xj Calculated as:

[0231]

[0232] Where, (Q f ) xj T j Period River Section R x The average flow of inland flow through the floodplain, that is, T j The average value of peak flow exceeding amortized flow in all floods during the period when peak flow is greater than flat flow; v xj T j Period River Section R x Average settling velocity of suspended sediment; (A f ) xj T j Period River Section R x The average floodplain area within the area.

[0233] T j Period River Section R x The amount of suspended sediment transported in irrigation or water diversion projects (O D ) xj Calculated as:

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

[0235] Where, (Q D ) xj T j Period River Section R x The average output flow in irrigation or water diversion projects, (C D ) xj T j Period River Section R xThe average sediment content of the output water in the irrigation or water diversion project. Both values ​​are obtained through the actual operation of the irrigation or water diversion project.

[0236] If there is hydrological sediment observation data at the entrance or exit of a reservoir or lake, the amount of sedimentation can be directly obtained from the data as T j Period River Section R x The amount of suspended sediment in the reservoir or lake (O R ) xj If not, then T j Period River Section R x The amount of suspended sediment in the reservoir or lake (O R ) xj Calculated as:

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

[0238] In the formula, TE xj T j Period River Section R x The average sediment retention rate of a reservoir or lake is calculated as:

[0239]

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

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

[0242] A second embodiment of the present invention provides a watershed sediment estimation device, comprising:

[0243] A basic data acquisition module is configured to collect basic data of the target watershed, including rainfall, soil, vegetation, topography, orthophotos, and hydrological data, organize the various basic data into a grid format and perform unified spatial registration, set the boundaries of the small watershed as the spatial unit for sediment estimation, spatially divide the various basic data based on the small watershed boundaries, and divide the various basic data at the small watershed scale into time periods based on the time scale requirements of the 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 temporal and spatial distribution of each type of erosion and the total erosion in the target watershed;

[0245] The sediment yield and deposition calculation module is configured to calculate the sediment yield and deposition corresponding to various types of erosion at the small watershed scale. For gravity erosion, the sediment yield is calculated based on the volume of river material input from collapses and landslides connected to the water system, and the sediment deposition at the small watershed scale is obtained by subtracting the sediment yield from the gravity erosion. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is first calculated, and then the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. The small watershed-scale sediment transport ratio 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 small watershed-scale sediment transport ratio for gully erosion and slope erosion is calculated based on the grid-scale sediment connectivity index within each small watershed. The spatiotemporal distribution of sediment yield and deposition in the target watershed is obtained based on the sediment yield and deposition of various types of erosion at the small watershed scale.

[0246] The suspended sediment transport calculation module is configured to calculate the suspended sediment transport of small basins in the main river system section by section based on the sediment yield of all small basins in the target basin in each time period, according to the upstream and downstream relationship of the locations where each small basin in the target basin flows into the river, and combine 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 above explanations of the embodiment of the method for estimating the watershed sediment are also applicable to the device for estimating the watershed sediment in this embodiment, and will not be repeated here.

[0248] In order to implement the above embodiment, the embodiment of the present invention further proposes a computer-readable storage medium on which a computer program is stored. The program is executed by a processor to execute the basin sediment estimation method of the above embodiment.

[0249] Reference below Figure 4 , which shows a schematic diagram of the structure of an electronic device suitable for implementing an embodiment of the present invention. It should be noted that the electronic devices in the embodiments of the present invention may include, but are not limited to, mobile terminals such as mobile phones, laptop computers, 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 only an example and should not limit the functions and scope of use of the embodiments of the present invention.

[0250] like Figure 4 As shown, the electronic device may include a processing device (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. Various programs and data required for the operation of the electronic device are also stored in the RAM 103. The processing device 101, the ROM 102, and the RAM 103 are connected to each other via a bus 104. An input / output (I / O) interface 105 is also connected to the bus 104.

[0251] Typically, the following devices may be connected to the I / O interface 105: an input device 106 including, for example, a touch screen, a touchpad, a keyboard, a mouse, a camera, a microphone, etc.; an output device 107 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; a storage device 108 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 109. The communication device 109 may allow the electronic device to communicate with other devices wirelessly or by wire to exchange data. Figure 4 The electronic device is shown with various devices, but it should be understood that it is not required to implement or possess all of the devices shown. More or fewer devices may be implemented or possessed instead.

[0252] In particular, according to an embodiment of the present invention, the process described above with reference to the flowchart can be implemented as a computer software program. 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 executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network via the communication device 109, or installed from the storage device 108, or installed from the ROM 102. When the computer program is executed by the processing device 101, the above-mentioned functions defined in the method of the embodiment of the present invention are performed.

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

[0254] The computer-readable medium may be included in the electronic device, or may exist independently without being incorporated into the electronic device.

[0255] The computer-readable medium carries one or more programs. When the one or more programs are executed by the electronic device, the electronic device executes the watershed sediment estimation method.

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

[0257] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0259] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application belong.

[0260] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the 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 (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program 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 the following: an electrical connection having one or more wires (electronic devices), a portable computer disk cartridge (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). Furthermore, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or otherwise processing it in a suitable manner if necessary, and then storing it in a computer memory.

[0261] It should be understood that various parts of the present 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 a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0262] Those skilled in the art will understand that all or part of the steps carried out in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the developed program can be stored in a computer-readable storage medium. When the program is executed, it includes one of the steps of the method embodiment or a combination thereof.

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

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

Claims

1. A method for estimating sediment in a watershed, characterized by: include: Step S1: Collect basic data of the target watershed, including rainfall, soil, vegetation, topography, orthophotos, and hydrological data; organize various basic data into a grid format and perform unified spatial registration; set small watershed boundaries as the spatial unit for sediment estimation; spatially divide various basic data based on the small watershed boundaries; and divide various basic data at the small watershed scale into time periods based on the time scale requirements of sediment estimation; 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, and obtain the spatiotemporal distribution of each type of erosion amount and the total erosion amount in the target watershed; Step S3: For gravity erosion, the sediment yield is calculated based on the volume of river material input from landslides and collapses connected to the water system, and the sediment yield is subtracted from the gravity erosion volume to obtain the sedimentation volume 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. Then, the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. The small watershed-scale sediment transport ratio 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 small watershed-scale sediment transport ratios for gully erosion and slope erosion are calculated based on the grid-scale sediment connectivity index within each small watershed. The temporal and spatial distribution of sediment yield and sedimentation in the target watershed is obtained based on the sediment yield and sedimentation of various erosion factors at the small watershed scale; Step S4: Based on the sediment yield of all small watersheds in the target watershed calculated in step S3 during each time period, the suspended sediment transport of the small watersheds in the main river system is calculated section by section according to the upstream and downstream relationship of the locations where each small watershed in the target watershed flows into the river. The distribution of the suspended sediment transport along the flow direction of the main river system is obtained by combining dredging, reservoir siltation, and the input and output of suspended sediment in the river section.

2. The basin sediment estimation method according to claim 1 is characterized in that: Among the basic data collected in step S1, the temporal resolution of rainfall data is not less than 3 hours; the soil data includes the organic matter content in sand, silt, and clay in the surface soil; the vegetation data includes the normalized vegetation index and vegetation type; the terrain data uses a digital elevation model with a spatial resolution of not less than 30 meters; the hydrological data includes river system data, flow, runoff, and sediment transport information within the target watershed; the basic data also includes land use type, which is used for the calculation of dimensionless soil and water conservation measure factors; the spatial resolution used when performing unified spatial registration on basic data in various grid forms is consistent with the spatial resolution of the digital elevation model; The small watershed is the watershed corresponding to the smallest level river in Horton's law. Based on the digital elevation model, the target watershed is divided into I small watersheds B1, B2, ... B i ,…B I , and statistics on the area, terrain elevation difference, average slope, channel length, channel width and channel slope of each small watershed.

3. The basin sediment estimation method according to claim 1 is characterized in that: In step S2, For gravity erosion, T is identified through multi-period orthophotos of the watershed. j The newly added collapse and landslide area during the period is counted based on the collapse and landslide area. j Time period small watershed B i The total volume of materials released by the collapse and landslide within the j Time period small watershed B i Gravity erosion (E G ) ij , T j It is a time unit determined according to the sediment estimation requirements, and the duration of each period ΔT is the same; For debris flow erosion, first obtain the small watershed B according to rainfall data. i In period T j All effective rainfall event information in the data, including the rainfall duration and average rainfall intensity of each effective rainfall event, is used to determine whether each effective rainfall event triggers a debris flow through the rainfall threshold trigger condition; When it is determined that an effective rainfall event does not trigger a debris flow, the volume of the outflow of the effective rainfall event is 0. When it is determined that an effective rainfall event triggers a debris flow, the volume of the outflow of the effective rainfall event is calculated. Statistics T j Time period small watershed B i The total volume of debris flow outflow is taken as T j Time period small watershed B i The amount of debris flow erosion (E D ) ij ; For channel erosion, T j Time period small watershed B i The channel in the channel is divided into several channel segments, and the channel erosion rate of each channel segment is calculated respectively. Based on the channel erosion rate, T is calculated. j Time period small watershed B i The amount of channel erosion (E g ) ij ; For slope erosion, the modified universal soil loss equation RUSLE is used to calculate the T of each grid. j The soil erosion modulus within the time period is then multiplied by the grid area to obtain the grid scale T j The amount of soil erosion in the period; the amount of soil erosion in the small watershed B i The soil erosion amount of each grid within the range is accumulated to obtain T j Time period small watershed B i The amount of slope erosion (E S ) ij ; The sum of the four types of erosion obtained is T j Small watershed B during the period i Total erosion (E) ij .

4. The basin sediment estimation method according to claim 3 is characterized in that: Calculate T according to the following formula j Time period small watershed B i Gravity erosion (E G ) ij : Where, ρ G is the density of the collapse and landslide material; (V G ) k T j Time period small watershed B i The volume of material released by the kth collapse and landslide in T j Time period small watershed B i The total number of internal collapse and landslides; the volume of material released by a single collapse and landslide V G Calculate according to the following formula: Where A G is the area of ​​a single collapse landslide; α and γ are coefficients, α is 0.05±0.02, γ is 1.1~1.3 for soil landslide, and γ is 1.3~1.6 for rock landslide; The small watershed B i In period T j All valid rainfall events in the data are obtained by following the steps below: First, the rainfall data after spatial division is calculated according to the following formula: τ Average rainfall in: Where, Small watershed B i In time period t τ Average rainfall in t τ is the temporal resolution of rainfall data, M is the temporal resolution of the small watershed B i The total number of grids within Small watershed B i The mth grid in the time period t τ of rainfall; Small watershed B i In time period t τ Average rainfall Divide by time period t τ As a small watershed B i In time period t τ Average rainfall intensity; Traverse each time period T j Obtain the rainfall intensity time series matrix of each small watershed, and determine the rainfall intensity of each small watershed in each period T in chronological order. j When the rainfall intensity is greater than the first set value, it is considered that a valid rainfall event has started. When the rainfall intensity is less than the first set value and continues for not less than the second set value, it is considered that the valid rainfall event has stopped. The period of time when the rainfall intensity is continuously greater than the first set value is considered as a valid rainfall event, and the rainfall duration D and average rainfall intensity of the valid rainfall event are recorded. Thus, we can obtain the small watershed B i In period T j All valid rainfall events information within; The rainfall threshold trigger condition is used to determine whether each effective rainfall event triggers a debris flow, specifically: Assume that the rainfall threshold is I c , according to the following formula with small watershed as the unit: I c =a D D -β Where, α D and β are both constants; When the average rainfall intensity of an effective rainfall event When , it is considered that no debris flow is triggered; When the average rainfall intensity of an effective rainfall event When the debris flow is triggered, the statistics of small watershed B i In T j The rainfall data P of each event that will trigger a debris flow during the period l (D l , ), where l is the number of rainfall events that will trigger debris flow, the total number is L events, D l and Small watershed B i In T j The duration and average rainfall intensity of the first rainfall event that will trigger a debris flow within the time period are used to calculate the volume of debris flow discharge V of each event using the following formula: D : Where Q D is the peak flow rate of debris flow; γ D is the bulk density of debris flow; γ W is the bulk density of clean water; S is the bulk density of solid matter in debris flow; Q P is the storm flood flow; K P is the confluence coefficient; F i Small watershed B i The drainage area; D C is the congestion coefficient; T is the duration of a debris flow; L D is the length of the main ditch of debris flow; U D is the speed of debris flow; S is the slope of gully bed; The T j Time period small watershed B i The amount of debris flow erosion (E D ) ij Calculate according to the following formula: Where, ρ D is the density of debris flow outflow material; (V D ) l T j Time period small watershed B i The volume of debris discharged from the first debris flow; The T j Time period small watershed B i The amount of channel erosion (E g ) ij Calculate according to the following formula: (E g ) ij =(G g ) ij ·ΔT Where, L s is the length of the s-th channel; r s is the annual average erosion rate of the slope of the channel section, which is taken as the annual average change rate of the cross section of the channel section; ρ is the density of eroded sediment; ΔT is T j the duration of the session; The T j Small watershed B during the period i The amount of slope erosion (E S ) ij Calculate according to the following formula: Where A g is the area of ​​a single grid; A m Small watershed B i Soil erosion modulus of the mth grid within the range; M is the soil erosion modulus of the small watershed B i The total number of grid cells within.

5. The basin sediment estimation method according to claim 3 is characterized in that: In step S3, Regarding the sand production and sedimentation caused by gravity erosion, if the collapse and landslide location is not connected to the river system, the sand production and sedimentation caused by gravity erosion caused by the collapse and landslide are both 0. If the collapse and landslide location is connected to the river system, the T j Time period small watershed B i Sedimentation 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 Where, (E G ) ij T j Time period small watershed B i The amount of gravity erosion; p and P are T j Time period small watershed B i Number and total number of collapses and landslides connected to the river system; T G The mass of material input to the river for a single landslide; w G is the average distance that a single landslide extends from the river bank into the water, based on historical remote sensing images or field surveys; L G is the length of the river section affected by a single collapse and landslide; k G is the correction coefficient; ρ is the density of eroded sediment; h is L G The average water depth of the corresponding river section; Q is the flow rate of the main river at the location of a single collapse and landslide; c and f are coefficients; T G ′ is T j Time period small watershed B i The amount of sediment produced corresponding to the amount of gravity erosion; Regarding the sand production and deposition caused by debris flow erosion, first calculate T according to the following formula: j Time period small watershed B i Sediment transport ratio (SDR) of internal debris flow erosion D ) ij : Where θ is T j Time period small watershed B i The angle at which the main ditch enters the main river; γ m and γ D T j Time period small watershed B i The bulk density of the main river and debris flow; q m and q D T j Time period small watershed B i The unit-width flow of the main river and debris flow is obtained based on the hydrological data, and the unit-width flow of the debris flow is calculated as q D =Q D / w D , w D T j Time period small watershed B i The width of the debris flow channel, Q D T j Time period small watershed B i Peak debris flow discharge; Then based on the sediment delivery ratio (SDR D ) ij Calculate T j Time period small watershed B i Sediment yield and sedimentation caused by debris flow erosion: (T D ) ij =(ED) ij ·(SDR D ) ij (D D ) ij =(E D ) ij -(T D ) ij Where, (T D ) ij T j Time period small watershed B i The amount of sediment produced by debris flow erosion (D D ) ij T j Time period small watershed B i the amount of sediment eroded by debris flows; For the sediment production and deposition of gully erosion and slope erosion, the T is first calculated based on the grid-scale sediment connectivity index in each small watershed. j Time period small watershed B i Sediment transport ratio (SDR) of gully erosion or slope erosion IC ) ij : Where, (SDR max ) ij It's T j Time period small watershed B i The theoretical maximum sediment transport ratio is related to the surface soil texture; IC ij T j Time period small watershed B i The average sediment connectivity index is taken as T j Time period small watershed B i The mean value of sediment connectivity index at each grid scale; IC0 and k are correction factors for calculating sediment transport ratio; Then based on the sediment delivery ratio (SDR IC ) ij Calculate T j Time period small watershed B i The sediment yield and deposition corresponding to the gully erosion, and the sediment yield and deposition corresponding to the 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 Where, (E g ) ij T j Time period small watershed B i The amount of channel erosion, (T g ) ij and (D g ) ij T j Time period small watershed B i The amount of sediment production and deposition corresponding to the amount of gully erosion; (E S ) ij T j Time period small watershed B i The amount of slope erosion, (T S ) ij and (D S ) ij T j Time period small watershed B i The amount of sediment production and deposition corresponding to the amount of slope erosion.

6. The basin sediment estimation method according to claim 5 is characterized in that: Assume that the grid-scale sediment connectivity index in a small watershed is IC, which can be calculated as follows: IS m =RI m +C·P Where D up is the upslope component of a small watershed, reflecting the sediment production potential of the upstream; is the average impedance factor of the upslope catchment area of ​​a small watershed, representing the resistance of surface roughness to the flow of water and sediment; is the average slope of the upslope catchment area of ​​a small watershed; A up is the upslope catchment area of ​​a small watershed; D dn is the downslope component of a small watershed, reflecting the path resistance of sediment to the target; d m is the length of the flow path of the mth grid in a small watershed along the steepest downslope direction; W m is the impedance factor of the mth grid in a small watershed; SS m IS is the slope gradient of the mth grid in a small watershed; max IS is the maximum surface index of the small watershed where the grid is located; m is the surface index of the mth grid in a small watershed; RI m is the roughness index of the mth grid in a small watershed; To calculate RI m Used in Grid moving scanning pane, x m is the elevation of a grid, x s For the surrounding of a certain grille is the average elevation of the grid; C is the dimensionless vegetation cover factor; P is the dimensionless soil and water conservation measure factor.

7. The basin sediment estimation method according to claim 1 is characterized in that: Step S4 specifically includes: According to the distribution of slope, river width and river type along the river, the river in the target basin is divided into X river sections R1, R2, ... R x ,…R X , stipulating that each river section shall have at most one reservoir or lake, and that the reservoir or lake shall be located at the entrance of the river section; Calculate the suspended sediment load of the river in the target basin section by section. j Any river section R in the period x The amount of suspended sediment output (SS out ) xj for: Where, (SS in ) xj T j River section R x The amount of suspended sediment input from upstream to the main river; (I T ) n For river section R x The amount of suspended sediment input from the nth tributary into the main river, n and N are the x The number and total number of internal tributaries, then Indicates T j Period River Section R x The amount of suspended sediment input from all tributaries into the main river is x The amount of suspended sediment that a tributary inputs into the main river I T , calculated based on the sediment yield of the small watershed obtained in step S3; (E B ) xj T j Period River Section R x The particle size of the riverbank erosion is consistent with the mass of the suspended sediment, which is calculated based on the water flow work; (O F ) xj T j Period River Section R x The amount of suspended sediment deposited on the floodplain is based on T j Period River Section R x The average flow rate through the floodplain, the average settling velocity of suspended sediment and the average area of ​​the floodplain are calculated; (O D ) xj T j Period River Section R x The amount of suspended sediment transported in irrigation or water diversion projects is based on T j Period River Section R x The average output flow and the average sediment content of the output water in the irrigation or water diversion project are calculated; (O R ) xj T j Period River Section R x The amount of suspended sediment deposition in reservoirs or lakes is obtained based on hydrological sediment observation data, or based on T j River section R x The amount of suspended sediment (SS in ) xj It is calculated based on the average sediment retention rate of the reservoir or lake.

8. The basin sediment estimation method according to claim 7 is characterized in that: The amount of suspended sediment input from a tributary into the main river in a single river section is calculated according to the following formula: T : I T =T G ′·(Δ s ) G +T D ·(Δ s ) D +T g ·(Δ s ) g +T S Where, T G ′ is T j Time period small watershed B i The amount of sediment produced corresponds to the amount of gravity erosion; T D is the sediment yield corresponding to the debris flow erosion of a small watershed corresponding to a tributary in a single river reach; T g is the sediment yield corresponding to the channel erosion of a small watershed corresponding to a tributary in a single river reach; T S is the sediment yield corresponding to the slope erosion of a small watershed corresponding to a tributary in a single river reach; (Δ s ) G 、(Δ s ) D 、(Δ s ) g T G ′、T D and T g The proportion of suspended sediment in the medium load is obtained by extracting the characteristic particle size proportion of suspended sediment in the target watershed from the gradation curves of collapse and landslide deposits, debris flow fan and channel slope materials; Calculate T according to the following formula j Period River Section R x The particle size of the riverbank erosion is consistent with the mass of the 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 ((D s ) B ) xj Where b is the adjustment parameter; the variable with subscript x represents the river section R x The average value, the subscript j represents the number of the time period; ρ w is the density of pure water; g is the acceleration due to gravity; Q B is the flow rate on the flat land of the river section; S is the slope of the river section; h B is the river bank height; L B is the length of the river section; ρ B is the density of the shore material; (Δ s ) B is the proportion of suspended sediment in the shore material; Calculate T according to the following formula j Period River Section R x The amount of suspended sediment deposited on the floodplain (O F ) xj : Where, (Q f ) xj T j Period River Section R x The average flow of inland flow through the floodplain, that is, T j The average value of peak flow exceeding amortized flow in all floods during the period when peak flow is greater than flat flow; v xj T j Period River Section R x Average settling velocity of suspended sediment; (A f ) xj T j Period River Section R x Average floodplain area within the Calculate T according to the following formula j Period River Section R x The amount of suspended sediment transported in irrigation or water diversion projects (O D ) xj : (Oh D ) xj =(Q D ) xj ·ΔT·(C D ) xj Where, (Q D ) xj T j Period River Section R x The average output flow in irrigation or water diversion projects, (C D ) xj T j Period River Section R x Average sediment content of output water from irrigation or water diversion projects; In the case where there is no hydrological sediment observation data at the entrance or exit of a reservoir or lake, T is calculated according to the following formula: j Period River Section R x The amount of suspended sediment in the reservoir or lake (O R ) xj : (Oh R ) xj =(SS in ) xj ·THE xj In the formula, TE xj T j Period River Section R x The average sediment retention rate of the reservoir or lake; C R is the effective storage capacity of the reservoir or lake; I R It is the average multi-year runoff of a reservoir or lake.

9. A basin sediment estimation device, characterized in that: include: A basic data acquisition module is configured to collect basic data of the target watershed, including rainfall, soil, vegetation, topography, and hydrological data, organize the various basic data into a grid format and perform unified spatial registration, set the boundaries of the small watershed as the spatial unit for sediment estimation, spatially divide the various basic data based on the small watershed boundaries, and divide the various basic data at the small watershed scale into time periods based on the time scale requirements of the 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, and obtain the temporal and spatial distribution of each type of erosion and the total erosion in the target watershed; The sediment yield and deposition calculation module is configured to calculate the sediment yield and deposition corresponding to various types of erosion at the small watershed scale. For gravity erosion, the sediment yield is calculated based on the volume of river material input from collapses and landslides connected to the water system, and the sediment deposition at the small watershed scale is obtained by subtracting the sediment yield from the gravity erosion. For debris flow erosion, gully erosion, and slope erosion, the sediment transport ratio at the small watershed scale is first calculated, and then the sediment yield and deposition at the small watershed scale are calculated based on the various sediment transport ratios. The small watershed-scale sediment transport ratio 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 small watershed-scale sediment transport ratio for gully erosion and slope erosion is calculated based on the grid-scale sediment connectivity index within each small watershed. The spatiotemporal distribution of sediment yield and deposition in the target watershed is obtained based on the sediment yield and deposition of various types of erosion at the small watershed scale. The suspended sediment transport calculation module is configured to calculate the suspended sediment transport of small basins in the main river system section by section based on the sediment yield of all small basins in the target basin in each time period, according to the upstream and downstream relationship of the locations where each small basin in the target basin flows into the river, and combine 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.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the watershed sediment estimation method according to any one of claims 1 to 8.

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