Threshold analysis of digital river network in Shanxi Province under different DEM resolutions
[Objective]In order to explore the optimal catchment area thresholds for extracting river networks using DEM data of different resolutions and to study the impact of thresholds on watershed hydrological information,[Methods]the DEM data with four different resolutions(12.5 m,30.0 m,90.0 m and 1 000.0 m)in Shanxi Province was used to extract the river networks and divide the watersheds using ArcGIS.The study determines the optimal thresholds through the river network density method and superimposed analysis with the actual river network and then investigates the impact of thresholds on the hydrological informa-tion of the watersheds.[Results]The result show that:(1)With 12.5 m DEM,when the threshold exceeds 10.000 km2,the river network level,the number of channels,and the length of channels at all levels stabilize,[Results]ing in the river network being classified into 6 levels,consistent with the actual river network.When the threshold value is 18.75 km2,the total length of the rivers is about 29 024 km,which is basically consistent with the actual river network.(2)The optimal thresholds determined for the four resolutions are 18.750 km2,22.500 km2,28.350 km2 and 40.000 km2,[Results]ing in the extracted river network closely resembling the actual river network.[Conclusion]The findings indicate the following:(1)Increasing the threshold leads to a sparser river network,[Results]ing in varying reductions in the number of river sources,river channels,and total channel length.If the threshold is too large,it may lead to the absence of main river channels and a shortened river network,failing to accurately represent the river network situation.(2)River network extraction is less impacted by DEM resolution but significantly affected by the thresholds.(3)Compared to the 90.0 m and 1 000.0 m DEMs,the river networks extracted by the 12.5 m and 30.0 m DEMs in the optimal thresholds match better with the actual river networks.Therefore,more accurate river networks in-formation requires higher resolution DEMs.(4)The thresholds also greatly influence watershed delineation.As the thresholds increase,the number of sub-watersheds decreases,the area of sub-watersheds increases,sub-watershed boundaries become simpler,and the total watershed area decreases.Therefore,the selection of the optimal thresholds should be based on the spe-cific application purpose and adjusted through comparison.Different resolutions of DEM data require the use of corresponding op-timal thresholds to ensure that the extraction result closely reflect the actual situation.
DEM resolutionGISdigital river networkcatchment area thresholdriver network density methodShanxi Prov-incerunoff
万方数据
维普
