Research On Flow Paths Algorithms And Its Application Based On Grid DEM

With more and more floods and other natural disasters occurring frequently in recentyears, the research object of watershed analysis based on DEM has been paid more and moreattention, the substance of the watershed analysis is morphological characteristic analysis ofthe terrain, and the focal point of the watershed analysis is the extraction of the morphologicalcharacteristic line of the terrain, besides, the simulation methods of extracting themorphological characteristic line of the terrain through calculating the regional catchmentarea are called flow paths algorithms. In the current common and mainstream flow pathsalgorithms based on grid DEM, the single flow direction algorithm has some shortcomingssuch as the low accuracy of flow direction, the single flow direction, the uneven distributionof water flow and the rest, which may lead to some errors on calculating the regionalcatchment area; although the multiple flow direction algorithm has considered the divergenceof water and the continuity of the flow direction, the flow direction is sole and single in somelocal special terrain locations such as narrow ditches and so on, that is, all water of the currentpoint should flow into the only grid point which locates on the lower place of the currentpoint. At this time, using the multiple flow direction algorithm may lead to some greatererrors in the calculation of the flow direction, which may also affect the accurate calculationof the regional catchment area.In order to solve this problem, a flow path algorithm is proposed, a piece of partialsurface is established through9grid points which act as the neighbors of the center grid pointand locate in the range of the3×3window, and through the contour curvature of the currentcenter grid point of the partial surface, the right single flow direction algorithm or the multipleflow direction algorithm will be determined which will be used to calculate the flow directionof the current grid point and its distribution ratio of the water flow. Meanwhile, consideringthe randomness of the water may also bring about some effect on aspects of the accuratecalculation of the flow direction and so on through using this flow path algorithm, the proposed flow path algorithm is improved with new control parameters which are thetangential curvature and the flow-path curvature, what’s more, some relevant accuracyevaluation of the improved flow path algorithm is made on the theoretical level.Finally, good results trough using this improved flow path algorithm in the calculation ofthe flow direction and the accumulation of the water are proved in watershed analysis, theextracted channel points meet the requirements, and this method also provides a solution forthe accurate extraction of the channel links and the divide links as well as the segmentation ofthe watershed terrain in the grid DEM region to a certain extent.