Research On Simulation Of Rainwater High Flood Level To Small And Medium-Sized Reservoir Based On 3D Virtual Scene

The flood disaster is one of the important ways to maintain energy balance for the nature.Humans build a variety of impoundment projects in order to seek the profits and avoid the damages from flood.However,our small and medium-sized reservoirs built during "the great leap forward" period failure frequently,and become potential safety hazards for the downstream masses.It is caused by their low construction standards,poor product quality,and lack of flood forecasting and dispatching system.Due to the economic and technical constraints,small and medium-sized reservoirs'ability to grasp the hydrological and meteorological data is far weaker than large reservoirs and rivers.Therefore,it is difficult to use relatively developed hydrological models directly.While after the catchments receiving rainstorm in flood season,traditional technical means based on storage capacity curve,regional flood risk map and 2D scale plate could not give a vivid expression on the potential flood threat in the effective period of future,especially the inundation shape on different part of dam.Therefore,targeted and adaptable flood warning methods for small and medium-sized reservoirs and a fast&intuitive simulation of water level for the reservoir area in 3D virtual scene could provide optimized decision support for the formation of flood scheduling scheme.It also has significant importance for the improvement of our reservoirs' flood forecasting&dispatching system,as well as the information management level.Under the conditions of less measured data,this paper develops an accumulative inflow flood volume calculation model for small and medium-sized reservoirs,which aims at heavy rainfall in flood season.Demonstration is the main traditional usage of building 3D models for the artificial construction.However,this paper builds a 3D virtual scene by seamlessly integrating dam model and the 3D GIS terrain in the reservoir area.The real and continuous underlying surface in the virtual scene benefits the flood inundation simulation and calculation of water level-reservoir capacity relationship.Based on the reckon of cumulative inflow capacity and optimized 3D virtual scene of the reservoir area,this paper realizes the visualization of high flood level both on terrain and dam construction.The research has some innovative results in the theories and methods for building the 3D GIS virtual scene and spatial analysis.It also provides a new computation&expression environment for flood risk and optimized scheduling to small and medium-sized reservoirs after heavy rainfall in flood season.The main research and results are as follows:(1)The catchment basins of small and medium-sized reservoirs in the lower-middle reaches of the Yangtze River have some certain characteristics,which are humid climate,rich vegetation,and relatively small area.A heavy rain in flood season could form a rapid convergence into the reservoir and threaten the entire area.This paper builds a double-layer early soil moisture model and runoff calculation model,which form the accumulative inflow flood volume calculation model for small and medium-sized reservoirs as a result.The upper soil of model receives rainfall and evaporation to take the surface runoff into being;the lower soil receives the leakage from above to shape the underground runoff;and the cumulative inflow capacity until the next day could be obtained by the runoff summation from both surface and underground.The relevant parameters for the HengShan reservoir are reckoned by the historical measured data of rainfall and water level in front of the dam.Select the single-day cumulative rainfall data greater than heavy rain to validate the model.The result shows that the calculation is relatively accurate for heavy rainstorm and above in flood season.On this basis,the model is applied to other small and medium-sized reservoirs to verify its applicability.They are also in the lower-middle reaches of the Yangtze River and have a substantially same environment on hydrological and meteorological conditions.With a clear target and less parameters,this model has some practical value in the flood prevention for small and medium-sized reservoirs in the lower-middle reaches of the Yangtze River.(2)This paper merges the GIS terrain and 3D dam model to form an integrated 3D virtual scene.It proposes a method to build a complete collection of discrete elevation points for the reservoir area on the basis of multi-source spatial data.This method preserves topographical features of the coast and islands.After analyzing the 3D model of artificial architectures,it draws a conclusion that the models have no internal topological relations,while the problems of vertex redundancy,surface cracks and voxels intersection exist.It designs a method to amend the dam model to a reasonable height in right proportion and posture through establishing adjective characteristic elevation planes.By extracting the fusion boundary,and eliminating the internal elevation points,terrain triangulation with holes is built in order to merge the dam model.This study solves the relatively independent and cracks&cross-cutting issues in building terrain and hydraulic constructions of traditional 3D virtual scene to reservoir area.Meanwhile,it provides a computation and visualization environment for fine simulation of water level in small and medium-sized reservoirs.(3)This paper designs an inundation algorithm for the 3D virtual scene based on the determined water level.The terrain submerged area is defined by adjacency iterative expansion;and inundated shape on the water side of the dam model is delimited by elevation comparison and intersection judgment on axis-aligned bounding boxes of discrete voxels.Thus,it provides a method to determine the water level-reservoir capacity relationship,which takes the surface morphology of important hydraulic constructions into account.This method effectively extends the capacity curve created by traditional methods.An optimization method for 3D virtual scene is designed for efficient-submerged simulation.Discretion of underlying surface topography and determine times of water level are controlled by accuracy and efficiency weight settings.Thereby,it provides simplified scenes for different water levels which improve the efficiency for water inundated simulation and rendering.This study broadens the applications of traditional 3D architectural models,and provides a guideline for spatial analysis involving artificial constructions and other special underlying surface morphology.(4)Take the HengShan reservoir in YiXing city as an example,this paper develops a prototype system of rainwater flood high level simulation to the small and medium-sized reservoir,and applies it into practical work of decision support on flood discharge and dispatch.After discussing its architecture,functional modules,core data structures and 3D visualization technology,this paper proves the accuracy and feasibility of the system through the calculation of accumulative inflow flood volume and simulation of rainwater flood high level during the heavy rainstorm happened on August 8th,which is in flood season of 2012.