Basin mountain torrent debris flow physical process simulation method for risk early warning

Abstract

The invention provides a drainage basin mountain torrent debris flow physical process simulation method for risk early warning, which comprises specific research and development contents and corresponding problems and achieves the following purposes: constructing a drainage basin unit database, clarifying drainage basin and channel characteristics, and providing data support based on physical process refined simulation; and carrying out basin hydrological process simulation research on the basis of the SWAT distributed model for improving glacier melt water simulation. A mountain torrent and debris flow disaster whole-process coupling model is constructed, a dynamic data chain is used for connecting watershed hydrology and a channel water and sediment dynamic process, full-link simulation from rainfall to disaster modeling is achieved, a disaster forming mechanism is accurately revealed, a visualization system is integrated through the model, channel disaster dynamic evolution evaluation and risk zoning functions are provided, and the reliability of channel disaster dynamic evolution evaluation is improved. A forecasting system designed in an object-oriented development mode can be seamlessly accessed to a provincial early warning platform, and a systematic solution is provided for early warning of watershed or regional disasters.

Description

Technical Field

[0001] The present invention relates to the technical field of disaster monitoring and early warning, and in particular to a method for simulating the physical process of mountain torrents and debris flows in a watershed for risk early warning. Background Art

[0002] Flash floods and debris flows often result from a chain reaction, typically triggered by heavy rainfall, snowmelt, or a combination of both. These events, driven by the basin's hydrological system, carry large amounts of sediment into channels. This dynamic action then triggers the rapid downstream movement of riverbed and bank material, ultimately breaking free from the channel at some point and causing flash floods and debris flows. From a fundamental perspective, the transition from precipitation / meltwater to channel runoff is a macroscopic process within the basin's hydrological cycle, encompassing the "four water transformations." The final formation of the disaster within the channel, however, stems from the evolution of water and sediment in the river channel, a more microscopic process involving channels and slopes. Furthermore, the two processes differ significantly in their timescales. The transition from basin precipitation to channel runoff typically occurs on a timescale of hours to days, while the transition from river confluence to disaster formation often occurs on a timescale of minutes to hours.

[0003] Currently, both hydrological models for simulating rainfall and runoff within a watershed and hydrodynamic models for simulating the evolution of solid-liquid two-phase flow within channels are relatively mature. However, from the perspective of the flash flood and debris flow chain, due to the insurmountable scale mismatch between the watershed hydrological processes and the evolution of water and sediment in the channels, both in time and space, there is a lack of systematic understanding of the entire process of flash flood and debris flow occurrence. This problem has prevented the current implementation of truly detailed simulations of the entire flash flood and debris flow disaster process in a specific single channel within the watershed unit, and is one of the main reasons for the difficulty in accurately assessing the specific distribution and causes of disasters within the region. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In response to the shortcomings of the existing technology, the present invention provides a method for simulating the physical processes of flash floods and debris flows in a watershed for risk early warning, focusing on solving the problems of unclear disaster mechanisms of flash floods and debris flows at the watershed scale due to different disaster environments and evolution processes, as well as inaccurate assessments of risk intensity, impact range, and affected objects.

[0006] Technical Solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a method for simulating the physical process of mountain torrents and debris flows in a watershed for risk warning, including the specific research and development content, corresponding problems, and the goals to be achieved as follows:

[0008] (1) Build a watershed unit database to clarify watershed and channel characteristics and provide data support for refined simulation based on physical processes;

[0009] (2) Carry out basin hydrological process simulation research based on the improved SWAT distributed model for glacial meltwater simulation, and provide the water and sediment inflow process of all channel cross-section nodes;

[0010] (3) Coupled with the channel-scale water-sediment dynamic model, simulate the initiation and transport of solid-liquid two-phase flow in the channel bed and bank slope during the channel evolution process, and provide forecasts of flash flood and debris flow disasters;

[0011] (4) Develop functional modules and integrate them to form a refined simulation platform for mountain torrents and debris flow processes in watershed units, and carry out demonstration applications in demonstration areas.

[0012] Preferably, the specific description of step (1) is as follows:

[0013] ① Collect and organize the important remote sensing data on topography, land use, soil type, etc. in the basin, and extract the river network distribution and connectivity in the basin based on comprehensive spatial analysis methods;

[0014] ② Collect and organize historical disaster information in the basin, conduct on-site disaster investigations, determine the locations of the main calculation nodes of the channel based on the disaster occurrence points and protected objects, and construct the river network topology relationship in the basin for simulation calculations;

[0015] ③ Carry out measurement of channel node cross-sectional morphology, investigation of riverbed composition, bank slope structure and other source distribution conditions, and on-site investigation of threat objects.

[0016] Preferably, the specific implementation of step (2) is as follows:

[0017] ① Improved water production simulation: Develop a dynamically changing glacier meltwater module based on the modified temperature index method and embed it into the SWAT model through an adapter interface for dynamic data interaction; simulate the physical hydrological processes of the watershed, including precipitation, snowmelt, vegetation interception, infiltration, surface runoff, subsurface flow, evaporation loss, and other water cycle elements, and determine the amount of precipitation / meltwater collected at channel nodes in the watershed;

[0018] ② Sediment production simulation: Based on the hydrological response units defined by topography, land use, and soil conditions, the erosion within the response units is calculated using a universal soil and water loss equation after considering the combined runoff from effective precipitation and meltwater.

[0019] ③ Calculate the hydraulic indicators of channel node sections: Analyze the heterogeneous distribution of runoff and sediment yields on the slope of the basin and the influencing factors, clarify the water and sediment inflow process of all calculation nodes in the river network, and calculate and determine the hydraulic indicators such as flow rate, flow velocity, water depth, and sediment content of the section nodes based on the channel section data, providing sub-hourly process information.

[0020] Preferably, the specific implementation of step (3) is as follows:

[0021] ① Model construction: Delineate the maximum threat range of flash flood debris flows in a single channel and use the finite volume method to discretize the model using an unstructured grid with a resolution no greater than 5m. A two-dimensional unsteady flow module for the Saint-Venant equation, a sediment transport module, and a Bingham fluid solid-liquid two-phase flow module are constructed to simulate the evolution of flash flood debris flows and the initiation and transport of channel material.

[0022] ② Model coupling: Automatically read the water and sediment indicators of sub-hourly river section nodes provided by the hydrological model, automatically conduct water and sediment dynamics simulations for all channels that exceed the warning flow / water level and have disaster risks, and set the read water and sediment indicators as dynamic initial control conditions; achieve coupling with the basin-scale hydrological model through dynamic data link connection;

[0023] ③ Disaster prediction: Analyze the spatiotemporal evolution of flow field, dynamic field, solid volume fraction, etc. during the evolution of water and sand in the channel. According to the damage such as inundation range, blockage and collapse, etc. that occurs during the evolution process, forecast the flash flood and mudslide disaster through the visualization of the dynamic evolution process.

[0024] Preferably, the specific implementation of step (iv) is as follows:

[0025] ① Module development: Through secondary development of the source code, the constructed SWAT model is recompiled and packaged to form a watershed hydrological simulation module; using Python third-party libraries, remote call and driver modules are developed for the constructed hydrodynamic model; based on Python, a pre-processing module for reading and writing early warning meteorological data is independently developed, as well as a post-processing module for reading simulation results and automatically generating disaster information;

[0026] ② System integration: According to the basic forecasting process of data reception, analysis and processing, model selection, forecasting operation and output of results, create a software system interface, design module interface and communication mechanism, integrate data, functional modules, visualization interface and users, and build an integrated platform for refined numerical simulation of mountain torrents and debris flows from watershed to channel.

[0027] (2) Beneficial effects

[0028] The present invention provides a method for simulating the physical process of mountain torrents and debris flows in a river basin for risk early warning. It has the following beneficial effects:

[0029] 1. Through dynamic data linking, the system couples the two key processes of watershed hydrology and channel water and sediment dynamics during flash floods and debris flows. This system simulates the entire process, from precipitation / meltwater, vegetation interception, runoff and infiltration, slope erosion, water and sediment collection, channel material mobilization, water and sediment evolution, inundation and scouring, and ultimately, disaster evolution, to reveal the mechanisms of flash floods and debris flows within a watershed unit.

[0030] 2. Through integrated development of coupled models, a visual representation of the dynamic evolution of flash flood and debris flow disasters in each channel is provided within a true watershed unit, enabling accurate assessment of flash flood and debris flow channel risks, impact inundation ranges, and potential disaster victims.

[0031] 3. The constructed forecast system adopts an object-oriented integrated development model, which can achieve the goal of model integration and access to the provincial monitoring and early warning platform at the basin or regional level. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the SWAT model of a method for simulating the physical process of mountain torrents and debris flows in a watershed for risk early warning proposed in the present invention; DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example:

[0035] like Figure 1 As shown, the embodiment of the present invention provides a method for simulating the physical process of mountain torrents and debris flows in a watershed for risk warning, including the specific research and development content, the corresponding problems, and the goals achieved as follows:

[0036] (1) Build a watershed unit database to clarify watershed and channel characteristics and provide data support for refined simulation based on physical processes;

[0037] (2) Carry out basin hydrological process simulation research based on the improved SWAT distributed model for glacial meltwater simulation, and provide the water and sediment inflow process of all channel cross-section nodes;

[0038] (3) Coupled with the channel-scale water-sediment dynamic model, simulate the initiation and transport of solid-liquid two-phase flow in the channel bed and bank slope during the channel evolution process, and provide forecasts of flash flood and debris flow disasters;

[0039] (4) Develop functional modules and integrate them to form a refined simulation platform for mountain torrents and debris flow processes in watershed units, and carry out demonstration applications in demonstration areas.

[0040] The specific description of step (1) is as follows:

[0041] ① Collect and organize the important remote sensing data on topography, land use, soil type, etc. in the basin, and extract the river network distribution and connectivity in the basin based on comprehensive spatial analysis methods;

[0042] ② Collect and organize historical disaster information in the basin, conduct on-site disaster investigations, determine the locations of the main calculation nodes of the channel based on the disaster occurrence points and protected objects, and construct the river network topology relationship in the basin for simulation calculations;

[0043] ③ Carry out measurement of channel node cross-sectional morphology, investigation of riverbed composition, bank slope structure and other source distribution conditions, and on-site investigation of threat objects.

[0044] The specific implementation of step (2) is as follows:

[0045] ① Improved water production simulation: Develop a dynamically changing glacier meltwater module based on the modified temperature index method and embed it into the SWAT model through an adapter interface for dynamic data interaction; simulate the physical hydrological processes of the watershed, including precipitation, snowmelt, vegetation interception, infiltration, surface runoff, subsurface flow, evaporation loss, and other water cycle elements, and determine the amount of precipitation / meltwater collected at channel nodes in the watershed;

[0046] ② Sediment production simulation: Based on the hydrological response units defined by topography, land use, and soil conditions, the erosion within the response units is calculated using a universal soil and water loss equation after considering the combined runoff from effective precipitation and meltwater.

[0047] ③ Calculate the hydraulic indicators of channel node sections: Analyze the heterogeneous distribution of runoff and sediment yields on the slope of the basin and the influencing factors, clarify the water and sediment inflow process of all calculation nodes in the river network, and calculate and determine the hydraulic indicators such as flow rate, flow velocity, water depth, and sediment content of the section nodes based on the channel section data, providing sub-hourly process information.

[0048] The specific implementation of step (three) is as follows:

[0049] ① Model construction: Delineate the maximum threat range of flash flood debris flows in a single channel and use the finite volume method to discretize the model using an unstructured grid with a resolution no greater than 5m. A two-dimensional unsteady flow module for the Saint-Venant equation, a sediment transport module, and a Bingham fluid solid-liquid two-phase flow module are constructed to simulate the evolution of flash flood debris flows and the initiation and transport of channel material.

[0050] ② Model coupling: Automatically read the water and sediment indicators of sub-hourly river section nodes provided by the hydrological model, automatically conduct water and sediment dynamics simulations for all channels that exceed the warning flow / water level and have disaster risks, and set the read water and sediment indicators as dynamic initial control conditions; achieve coupling with the basin-scale hydrological model through dynamic data link connection;

[0051] ③ Disaster prediction: Analyze the spatiotemporal evolution of flow field, dynamic field, solid volume fraction, etc. during the evolution of water and sand in the channel. According to the damage such as inundation range, blockage and collapse, etc. that occurs during the evolution process, forecast the flash flood and mudslide disaster through the visualization of the dynamic evolution process.

[0052] The specific implementation of step (four) is as follows:

[0053] ① Module development: Through secondary development of the source code, the constructed SWAT model is recompiled and packaged to form a watershed hydrological simulation module; using Python third-party libraries, remote call and driver modules are developed for the constructed hydrodynamic model; based on Python, a pre-processing module for reading and writing early warning meteorological data is independently developed, as well as a post-processing module for reading simulation results and automatically generating disaster information;

[0054] ② System integration: According to the basic forecasting process of data reception, analysis and processing, model selection, forecasting operation and output of results, create a software system interface, design module interface and communication mechanism, integrate data, functional modules, visualization interface and users, and build an integrated platform for refined numerical simulation of mountain torrents and debris flows from watershed to channel.

[0055] The technical indicators obtained from the simulation method are as follows:

[0056] (1) Simulation refinement index

[0057] Through data link connection, the coupled simulation of the watershed water production process and the river channel water and sediment evolution process is completed, achieving a refined expression of the entire physical process including precipitation / meltwater, vegetation interception, runoff and infiltration, slope erosion, water and sediment collection, channel material initiation, water and sediment evolution, inundation and scouring damage, and disaster evolution;

[0058] At the basin scale, distributed water and sediment production simulations are carried out with the hydrological response unit as the smallest calculation unit to accurately depict the impact of spatial heterogeneity in the basin's topography, land use and soil conditions. At the channel scale, the finite volume method is used to discretize unstructured grids with a maximum spatial resolution of 5m and a minimum spatial resolution of 0.5m to achieve refined simulation of the water and sediment evolution process in the channel and within the influence range on both sides.

[0059] (2) Indicators for generating disaster warning information

[0060] Water and sediment production are simulated uniformly within the watershed, while water and sediment evolution is simulated simultaneously using different hydrodynamic models within the channel. Parallel computation of multiple hydrodynamic models ensures that the time from receiving meteorological warning information to generating a disaster alert is no more than 15 minutes. Dynamic updates are synchronized with weather forecasts, with a maximum time span of seven days generated based on data from the weather forecast network. Spatial coverage enables disaster forecasts for every section of all channels within the watershed.

[0061] (3) Accuracy index of early warning information

[0062] The coupled hydrological model and hydrodynamic model have a good application foundation around the world. The accuracy of SWAT in forecasting basin runoff flood events is over 70%, and the restoration rate of the hydrodynamic model in simulating single mountain torrents and debris flow disasters is over 90%.

[0063] Considering that this scheme can reduce the uncertainty of the model in terms of data completeness, the final application can ensure that the accuracy of the simulation of mountain torrent and debris flow disasters in the basin is not less than 75%, and the false alarm rate is not less than 15%.

[0064] (IV) Other indicators

[0065] The integrated early warning platform is based on modular integrated development and can read weather forecast data of different structural types such as sites and grids during data acquisition;

[0066] Disaster information including the disaster evolution process can be connected to the specific needs of the disaster relief platform.

[0067] Physical process-based simulations can also provide results for the analysis of the mechanisms of flash flood and debris flow disasters, including dynamic changes in glacier snow, evaporation loss, soil moisture content, surface water and groundwater recharge, slope erosion, mud and sand content in channel sections, dynamic fields and flow field distribution, riverbed and bank slope erosion, and other hydrological and hydrodynamic factors.

[0068] The SAWT improvement method is:

[0069] Improved water production simulation: Specifically, the glacier meltwater simulation is added to enable SWAT to meet the characteristics of "rain, snow, and ice" runoff in mountainous areas in water production simulation. A dynamically changing glacier meltwater module is developed using the modified temperature index method and embedded into the SWAT model through an adapter interface for dynamic data interaction. The specific model diagram is as follows: Figure 1 .

[0070] Figure 1 The overall classification of the SWAT model is:

[0071] Hydrological processes: precipitation, glacial input, rainfall, snowfall, freezing, snow sublimation, vegetation interception, interception evaporation, snowmelt, icemelt, infiltration, surface interception, soil water movement, runoff loss, soil evaporation, subsoil flow, infiltration, water withdrawal, evaporation, seepage, and baseflow.

[0072] Water storage forms: ice storage, snow accumulation, soil water storage, river runoff, shallow aquifers, and deep aquifers.

[0073] and Figure 1 The overall process of the SWAT model is:

[0074] Precipitation part:

[0075] Precipitation occurs primarily in the form of rain and snow. During rainfall, some rainwater is intercepted by vegetation and stored on the surface of branches and leaves. It then evaporates and re-enters the atmosphere. Snowfall forms snowpack, which can sublimate, transforming directly from a solid to a gaseous state and returning to the atmosphere. Alternatively, it can melt under rising temperatures, forming snowmelt, which contributes to subsequent flows such as surface runoff.

[0076] Surface runoff and infiltration stages

[0077] Surface runoff: Precipitation that is not intercepted by vegetation and snowmelt will gather on the surface to form surface runoff. Surface runoff will flow to low-lying areas, such as into rivers to form river runoff. At the same time, there may be runoff losses during the flow process.

[0078] Infiltration: Some water will seep downward into the soil under the influence of gravity and other factors, increasing the soil water storage capacity. Soil water storage will further cause soil water movement, such as soil evaporation or soil flow and infiltration into deeper soil layers.

[0079] Soil water movement and groundwater stages

[0080] When soil water infiltrates to a certain depth, it reaches shallow aquifers. While this water can be used by people, it can also evaporate and seep deeper, forming underground baseflow. Some of this shallow aquifer water continues to infiltrate deeper aquifers, while underground baseflow merges with river runoff.

[0081] Glacier input section:

[0082] The ice input from glaciers and the frozen part after snowfall will be stored as ice. As the temperature rises and other conditions change, the stored ice will melt. The water from the melted stored ice will also participate in subsequent links such as surface runoff together with the water produced by the melted snow.

[0083] The dynamic data link integration includes:

[0084] This technology uses a hydrological model and a hydrodynamic model to simulate flash floods and debris flows at the channel scale within the basin. The two-scale models are coupled and integrated through a dynamic data link. Specifically:

[0085] ①The system automatically reads meteorological data;

[0086] ② Update the driving data set of the SWAT model after processing;

[0087] ③ Generate runoff data of channel sections after SWAT simulation;

[0088] ④ Then, based on the collected large-section data, convert the runoff data into hydraulic element data such as water depth and flow velocity;

[0089] ⑤Transfer hydraulic element data to the HEC-RAS model to simulate flooding at the channel scale;

[0090] ⑥ Generate the final disaster information such as flooding range, flooding duration, flooding depth, etc. The above steps are executed regularly and updated dynamically according to the update frequency of weather forecast data.

[0091] The research and development direction starts from the simulation description of the whole process of the formation of mountain torrent and mud-rock flow disasters, provides a systematic understanding of the disaster, and develops a forecast platform according to the forecast process of data reception, analysis and processing, model selection, forecast operation and results output.

[0092] The SWAT model involved is an open source model that can be compiled and packaged twice; Python provides a third-party library to drive hydrodynamic simulation operations. The conditions for conducting coupled simulations of two-scale models are basically mature, making the integrated development of a refined simulation platform from data acquisition to forecast information release completely feasible.

[0093] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for simulating the physical process of mountain torrents and debris flows in a river basin for risk early warning, characterized by: The specific research and development contents, corresponding problems and goals to be achieved are as follows: (1) Build a watershed unit database to clarify watershed and channel characteristics and provide data support for refined simulation based on physical processes; (2) Carry out basin hydrological process simulation research based on the improved SWAT distributed model for glacial meltwater simulation, and provide the water and sediment inflow process of all channel cross-section nodes; (3) Coupled with the channel-scale water-sediment dynamic model, simulate the initiation and transport of solid-liquid two-phase flow in the channel bed and bank slope during the channel evolution process, and provide forecasts of flash flood and debris flow disasters; (4) Develop functional modules and integrate them to form a refined simulation platform for mountain torrents and debris flow processes in watershed units, and carry out demonstration applications in demonstration areas.

2. The method for simulating the physical process of mountain torrents and debris flows in a watershed for risk warning according to claim 1, characterized in that: The specific description of step (1) is as follows: ① Collect and organize the important remote sensing data on topography, land use, soil type, etc. in the basin, and extract the river network distribution and connectivity in the basin based on comprehensive spatial analysis methods; ② Collect and organize historical disaster information in the basin, conduct on-site disaster investigations, determine the locations of the main calculation nodes of the channel based on the disaster occurrence points and protected objects, and construct the river network topology relationship in the basin for simulation calculations; ③ Carry out measurement of channel node cross-sectional morphology, investigation of riverbed composition, bank slope structure and other source distribution conditions, and on-site investigation of threat objects.

3. The method for simulating the physical process of mountain torrents and debris flows in a watershed for risk warning according to claim 1, characterized in that: The specific implementation of step (2) is as follows: ① Improved water production simulation: Develop a dynamically changing glacier meltwater module based on the modified temperature index method and embed it into the SWAT model through an adapter interface for dynamic data interaction; simulate the physical hydrological processes of the watershed, including precipitation, snowmelt, vegetation interception, infiltration, surface runoff, subsurface flow, evaporation loss, and other water cycle elements, and determine the amount of precipitation / meltwater collected at channel nodes in the watershed; ② Sediment production simulation: Based on the hydrological response units defined by topography, land use, and soil conditions, the erosion within the response units is calculated using a universal soil and water loss equation after considering the combined runoff from effective precipitation and meltwater. ③ Calculate the hydraulic indicators of channel node sections: Analyze the heterogeneous distribution of runoff and sediment yields on the slope of the basin and the influencing factors, clarify the water and sediment inflow process of all calculation nodes in the river network, and calculate and determine the hydraulic indicators such as flow rate, flow velocity, water depth, and sediment content of the section nodes based on the channel section data, providing sub-hourly process information.

4. The method for simulating the physical process of mountain torrents and debris flows in a watershed for risk warning according to claim 1, characterized in that: The specific implementation of step (3) is as follows: ① Model construction: Delineate the maximum threat range of flash flood debris flows in a single channel and use the finite volume method to discretize the model using an unstructured grid with a resolution no greater than 5m. A two-dimensional unsteady flow module for the Saint-Venant equation, a sediment transport module, and a Bingham fluid solid-liquid two-phase flow module are constructed to simulate the evolution of flash flood debris flows and the initiation and transport of channel material. ② Model coupling: Automatically read the water and sediment indicators of sub-hourly river section nodes provided by the hydrological model, automatically conduct water and sediment dynamics simulations for all channels that exceed the warning flow / water level and have disaster risks, and set the read water and sediment indicators as dynamic initial control conditions; achieve coupling with the basin-scale hydrological model through dynamic data link connection; ③ Disaster prediction: Analyze the spatiotemporal evolution of flow field, dynamic field, solid volume fraction, etc. during the evolution of water and sand in the channel. According to the damage such as inundation range, blockage and collapse, etc. that occurs during the evolution process, forecast the flash flood and mudslide disaster through the visualization of the dynamic evolution process.

5. The method for simulating the physical process of mountain torrents and debris flows in a watershed for risk early warning according to claim 1, characterized in that: The specific implementation of the step (four) is as follows: ① Module development: Through secondary development of source code, the constructed SWAT model is recompiled and packaged to form a watershed hydrological simulation module; through Python third-party libraries, remote call and driver modules are developed for the constructed hydrodynamic model; Independently develop a pre-processing module for reading and writing early warning meteorological data based on Python, as well as a post-processing module for reading simulation results and automatically generating disaster information; ② System integration: According to the basic forecasting process of data reception, analysis and processing, model selection, forecasting operation and output of results, create a software system interface, design module interface and communication mechanism, integrate data, functional modules, visualization interface and users, and build an integrated platform for refined numerical simulation of mountain torrents and debris flows from watershed to channel.

Images