A calculation method for obtaining flood peak flow based on remote sensing images

Abstract

The present invention relates to a method for calculating peak flow rate based on remote sensing images, and belongs to the technical field of river channel measurement and peak flow monitoring. The key parameters of the river channel section are obtained through river channel section survey data; radar remote sensing image data is obtained, and the elevation information of the river channel section in the remote sensing image is extracted to obtain the elevation information H1 of the river channel section at the initial time T1 and the elevation information H2 of the river channel section at the end time T2, and the water depth h1 of the river channel section at the initial time and the water depth h2 of the river channel section at the end time are calculated; radar remote sensing is used to obtain the length L of the water flow path in the time period T2#imgabs0#T1; the water volume in the time period is regarded as the volume of a tetrahedron, and the flow rate in the unit time period is calculated to obtain the peak flow rate. The method of the present invention can respond quickly when dealing with sudden flood disasters, which can not only effectively reduce the investment of manpower and material resources, but also realize efficient, rapid and comprehensive normalized monitoring of the peak flow rate, and improve the efficiency of water resource management.

Description

Technical Field

[0001] The invention relates to a calculation method for obtaining flood peak flow based on remote sensing images, and belongs to the technical field of river channel measurement and flood peak monitoring. Background Art

[0002] Peak flow refers to the flow when the water level in a river or river reaches the highest peak within a certain period of time, usually in cubic meters per second. The formation of peak flow is mainly when the rainfall is heavy, the soil cannot fully absorb and store water, and the surface runoff will flow into the river in large quantities, causing the river water level to rise. It is a natural phenomenon in nature and has important significance and influence in rivers. If the rainfall continues to increase and exceeds the water-carrying capacity of the river, it will lead to the appearance of peak flow. The study of peak flow is of great significance to flood prevention and disaster reduction, water resources utilization and ecological environmental protection.

[0003] At present, the calculation methods of peak flow are mainly divided into direct observation and indirect measurement. Direct observation is mainly based on the buoy flow measurement method, which is easy to use and fast, but the entire test process requires personnel cooperation. The peak flow is often accompanied by a relatively bad weather environment, which requires a lot of manpower and material costs. Indirect observation is mainly based on hydrological model calculation. Through a certain mathematical model, the hydrological process and flood generation process are simulated to calculate the peak flow. However, the parameters of the hydrological model usually need to be set according to historical data or expert experience. This setting method may be affected by many factors, resulting in uncertainty in the model parameters. This uncertainty may affect the prediction accuracy and reliability of the model, and thus affect the accuracy of the peak flow estimation. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a calculation method for obtaining peak flow based on remote sensing images. Based on the river section survey data and combined with remote sensing images to calculate the peak flow, it can effectively reduce the waste of manpower and material resources and realize the normalized monitoring of peak flow. It can be applied to the calculation of multiple factors such as water flow resistance, water flow loss, and ecological water storage capacity of the river.

[0005] The technical solution adopted by the present invention is:

[0006] A method for calculating flood peak flow based on remote sensing images includes the following steps:

[0007] S1. Obtain key parameters of the river section through river section survey data, including riverbed elevation H0; riverbed width B, right bank slope coefficient m1, and left bank slope coefficient m2;

[0008] S2. Acquire radar remote sensing image data, extract elevation information of the river section in the remote sensing image, obtain elevation information H1 of the river section at the initial time T1, elevation information H2 of the river section at the end time T2, and calculate the water depth h1 of the river section at the initial time and the water depth h2 of the river section at the end time;

[0009] S3. Obtaining T2 using radar remote sensing The length of the water flow path in the T1 period is L;

[0010] S4. Based on the above radar remote sensing data and key parameters of the river section, T2 The water volume in the T1 time period is regarded as the volume of a tetrahedron, and the flow rate Q in the unit time period is calculated to obtain the peak flow rate:

[0011] .

[0012] In the above method,

[0013] The calculation formula of the water depth of the river section in step S2 is:

[0014] h1=H1-H0,

[0015] h2=H2-H0,

[0016] H0: river bottom elevation,

[0017] H1: river section elevation at the initial moment,

[0018] H2: river section elevation at the end time,

[0019] h1: water depth of the river section at the initial time T1,

[0020] h2: Water depth of river section T2 at the end time.

[0021] The method for obtaining the water flow path length L in the time period in step S3 is: use a drone or other platform equipped with a radar to scan the target river channel, obtain the flow velocity data on the river surface, and obtain the water flow path length L in the time period by integrating the flow velocity data with the time period.

[0022] ,

[0023] L: length of water flow path within the time period,

[0024] T1: initial time,

[0025] T2: Ending time,

[0026] V1: water flow velocity measured by radar at the initial moment,

[0027] V2: Water flow velocity measured by radar at the end time.

[0028] The calculation process of the peak flow in step S4 is:

[0029] (1) First calculate the water flow in each time period. The river section at the initial time T1 is a trapezoid. During the T1 period, the river section corresponding to the T2 time is also a trapezoid. The water volume in the T1 time period is regarded as the volume of a tetrahedron, and the water volume is calculated according to the tetrahedron volume formula:

[0030] ,

[0031] V: The volume of the pyramid, that is, the amount of water flowing through it.

[0032] S 上底 : The cross-sectional area of ​​the river at the initial time T1,

[0033] S 下底 : The cross-sectional area of ​​the river at the end time T2,

[0034] L: length of water flow path in the time period;

[0035] Where S 上底 The calculation process is:

[0036] The river section at the initial time T1, according to the definition of slope coefficient, b 左1 =m1×h1,b 右1 =m2×h1,

[0037] S 上底 = (2B+ m1h1+ m2h1)h1 / 2,

[0038] b 左1 : The horizontal projection length of the left slope of the river section at the initial time T1,

[0039] b 右1 : The horizontal projection length of the right slope of the river section at the initial time T1,

[0040] h1: water depth of the river section at the initial time T1;

[0041] S 下底 The calculation process is:

[0042] The river section at the end time T2, according to the definition of slope coefficient, b 左2 =m1×h2,b 右2 =m2×h2,

[0043] S 下底=(2B+ m1h2+ m2h2)h2 / 2,

[0044] b 左2 : The horizontal projection length of the left slope of the river section at the end time T2,

[0045] b 右2 : The horizontal projection length of the right slope of the river section at the end time T2,

[0046] h2: water depth of the river section at the end time T2;

[0047] The calculated S 上底 and S 下底 Substituting into the above formula V, we get:

[0048] ;

[0049] (2) The flow rate within a unit period is calculated as:

[0050] ,

[0051] Substituting the water flow rate V calculated in the above formula into the time period, we get:

[0052] ,

[0053] Q is the peak flow.

[0054] The beneficial effects of the present invention are:

[0055] The present invention can calculate the peak flow rate using radar satellite remote sensing data for some rivers with complex cross-section conditions, combined with basic data from river survey and measurement. Through remote sensing, it is possible to respond quickly to sudden flood disasters and provide strong support for flood control and drought relief. It can not only effectively reduce the investment in manpower and material resources, but also realize efficient, rapid and comprehensive normalized monitoring of peak flow rates, improve water resources management efficiency, and provide important data support and decision-making basis for flood control and drought relief. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a flow chart of the method of the present invention;

[0057] Figure 2 This is a model diagram for flow rate calculation in the method of the present invention. DETAILED DESCRIPTION

[0058] The following is further described in conjunction with specific embodiments.

[0059] Embodiment 1 A method for calculating flood peak flow based on remote sensing images comprises the following steps:

[0060] S1. Obtain key parameters of the river section through river section survey data, including riverbed elevation H0; riverbed width B, right bank slope coefficient m1, and left bank slope coefficient m2:

[0061] Through basic measurement information such as engineering design drawings and river section survey drawings, several key parameters of a river section can be known, including riverbed elevation H0, riverbed width B, right bank slope coefficient m1, and left bank slope coefficient m2.

[0062] According to the definition of slope coefficient:

[0063] ,

[0064] ,

[0065] b 左 : Projection length of the left slope in the horizontal direction (m),

[0066] b 右 : Projection length of the right slope in the horizontal direction (m),

[0067] h: water depth of river section (m).

[0068] S2. Obtain radar remote sensing image data, extract the elevation information of the river section in the remote sensing image, obtain the elevation information H1 of the river section at the initial time T1, the elevation information H2 of the river section at the end time T2, and calculate the water depth h1 of the river section at the initial time and the water depth h2 of the river section at the end time:

[0069] First, phase unwrapping is performed on the radar image data to eliminate phase ambiguity. Then, filtering and denoising are performed to improve the quality and accuracy of the data. Finally, an interference pattern is generated based on the processed data, and the elevation information of the surface is extracted using the conversion relationship from phase to elevation. A continuous DEM is constructed through interpolation and gridding. Further, the elevation information H1 of the river section at the initial time T1 is obtained, and the elevation information H2 of the river section at the end time T2 is obtained by radar remote sensing data. The water depth of the river section at the initial period and the water depth of the river section at the end period are:

[0070] h1=H1-H0,

[0071] h2=H2-H0,

[0072] T1: initial time (s),

[0073] T2: End time (s),

[0074] H0: river bottom elevation (m),

[0075] H1: river section elevation at the initial moment (m),

[0076] H2: river section elevation at the end time (m),

[0077] h1: water depth of the river section at the initial time T1 (m),

[0078] h2: Water depth of the river section at the end time T2 (m).

[0079] S3. Obtaining T2 using radar remote sensing The length of the water flow path L during the T1 period:

[0080] Radar remote sensing technology mainly relies on its non-contact measurement capability and high-precision data processing capability to obtain the length of the water flow path within a time period. The collected radar data needs to be preprocessed, including denoising, filtering, calibration and other steps to improve the accuracy and reliability of the data. Use a drone or other platform equipped with radar to scan the target river channel to obtain the flow velocity data on the river surface, and obtain the length of the water flow path L within the time period by integrating the flow velocity data with the time period.

[0081] For example, if the flow velocity is 2 m / s at T2=1s and 3 m / s at T1=2s, the path length is:

[0082] ,

[0083] T1: initial time (s),

[0084] T2: End time (s),

[0085] V1: water flow velocity measured by radar at the initial moment (m / s),

[0086] V2: Water flow velocity measured by radar at the end time (m / s).

[0087] S4. According to the radar remote sensing data and river section parameters, T2 The water volume in the T1 time period is regarded as the volume of a tetrahedron, and the flow rate Q in the unit time period is calculated to obtain the peak flow rate:

[0088] (1) First calculate the water flow in each time period. The river section at the initial time T1 is a trapezoid. During the T1 period, the river section corresponding to the T2 time is also a trapezoid. The volume of water in the T1 period is regarded as the volume of a tetrahedron (e.g. Figure 2 ), calculate the water flow rate according to the volume formula of the tetrahedron:

[0089] ,

[0090] V: The volume of the tetrahedron, i.e. the amount of water flowing through it, (m 3 )

[0091] S 上底 : The cross-sectional area of ​​the river at the initial time T1 (m 2 ),

[0092] S 下底 : The cross-sectional area of ​​the river at the end time T2 (m 2 ),

[0093] L: length of water flow path in the time period L (m);

[0094] Where S 上底 The calculation process is:

[0095] The river section at the initial time T1, according to the definition of slope coefficient, b 左1 =m1×h1,b 右1 =m2×h1,

[0096] S 上底 = (2B+ m1h1+ m2h1)h1 / 2,

[0097] b 左1 : The horizontal projection length of the left slope of the river section at the initial time T1 (m),

[0098] b 右1 : The horizontal projection length of the right slope of the river section at the initial time T1 (m),

[0099] h1: water depth of the river section at the initial time T1 (m);

[0100] S 下底 The calculation process is:

[0101] The river section at the end time T2, according to the definition of slope coefficient, b 左2 =m1×h2,b 右2 =m2×h2,

[0102] S 下底 =(2B+ m1h2+ m2h2)h2 / 2,

[0103] b 左2 : The horizontal projection length of the left slope of the river section at the initial time T1 (m),

[0104] b 右2 : The horizontal projection length of the right slope of the river section at the initial time T1 (m),

[0105] h2: water depth of the river section at the initial time T1 (m);

[0106] The calculated S 上底 and S 下底 Substituting into the above formula V, we get:

[0107] ,

[0108] (2) The flow rate within a unit period is calculated as:

[0109] ,

[0110] T1: initial time (s),

[0111] T2: End time (s),

[0112] Substituting the water flow rate V calculated in the above formula into the time period, we can get

[0113] ,

[0114] Q is the peak flow.

[0115] Example 1: When calculating and analyzing the peak flow of a river section, the basic hydrological survey data of the section is first obtained. According to the survey data of the section, the riverbed width of the lower section of the river section is B, which is 45m, the right bank slope coefficient m2 of the river section is 2.5, the left bank slope coefficient m1 of the river section is 2.5, and the riverbed elevation is 49m.

[0116] To obtain the remote sensing image covering the river section, the image data covering the section can be obtained by downloading radar remote sensing image data.

[0117] When the initial time (T2)-the end time (T1)=1s, the initial time period elevation information H1 and the end time period elevation information H2 are extracted from the image data.

[0118] The initial elevation information of the river section is extracted as H1, which is 50, and the final elevation information is extracted as H2, which is 50.2, and H0 is 49.8. h1=H1-H0 and h2=H2-H0 are used, h1=0.2, h2=0.4,

[0119] According to S3, the length of the river section L is extracted from the image data, and the length of the river section L is 2m, and T2 T1=1, and we can get

[0120] ,

[0121] Q=62.32

[0122] Therefore, the current peak flow of the river section is 62.32m 3 / s.

[0123] The above is a further description of the present invention in combination with the embodiments, and the protection scope of the present invention is not limited thereto.

Claims

1. A method for calculating flood peak flow based on remote sensing images, characterized in that: The steps include: S1. Obtain key parameters of the river section through river section survey data, including riverbed elevation H0; riverbed width B, right bank slope coefficient m1, and left bank slope coefficient m2; S2. Acquire radar remote sensing image data, extract elevation information of the river section in the remote sensing image, obtain elevation information H1 of the river section at the initial time T1, elevation information H2 of the river section at the end time T2, and calculate the water depth h1 of the river section at the initial time and the water depth h2 of the river section at the end time; S3. Obtaining T2 using radar remote sensing The length of the water flow path L in the time period T1; the method for obtaining the length of the water flow path L in the time period is: use a drone or other platform equipped with radar to scan the target river channel, obtain the flow velocity data on the river surface, and obtain the length of the water flow path L in the time period by integrating the flow velocity data with the time period. ， L: length of water flow path within the time period, T1: initial time, T2: Ending time, V1: water flow velocity measured by radar at the initial moment, V2: water flow velocity measured by radar at the end time; S4. Based on the above radar remote sensing data and key parameters of the river section, first calculate the river section area S at the initial time T1 上底 and the river cross-sectional area S at the end time T2 下底 Calculate S according to the trapezoidal area based on the right bank slope coefficient m1, the left bank slope coefficient m2, the river bottom width B and the river section water depth h1 at the initial time T1 上底 Calculate S according to the trapezoidal area based on the right bank slope coefficient m1, the left bank slope coefficient m2, the river bottom width B and the river section water depth h2 at the end time T2 下底 ; The river section at the initial time T1 is a trapezoid. During the T1 period, the river section corresponding to the T2 time is also a trapezoid. The water volume in the T1 time period is regarded as the volume of a tetrahedron, and the water flow V in the time period is calculated according to the tetrahedron volume formula; The flow rate Q in a unit time period is calculated using the water flow V in the time period, which is the peak flow rate. 。 2. The method for calculating flood peak flow based on remote sensing images according to claim 1 is characterized in that: The calculation formula of the water depth of the river section in step S2 is: h1=H1-H0, h2=H2-H0, H0: river bottom elevation, H1: river section elevation at the initial moment, H2: river section elevation at the end time, h1: water depth of the river section at the initial time T1, h2: Water depth of river section T2 at the end time.

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