Impact of urbanization on stream structure and flood hazard in the plain river network region

Urbanization is one of the most intensive processes of human activities which have changed the earth´s surface, and is also one of the important factors influencing the hydrologic process. Base on the high resolution image and topographic map, this paper conducts a case study on the flood response to river system change under urbanization in a typical plain river network region of Fenghuajiang River basin. The result showed that the proportion of urban area was increased from 13.2% to 34.1% during the past 20 years, which was mainly gained from cropland and water bodies; the increase of impervious surface tended to produce more surface runoff, and also decrease the drainage density and water surface rates. The submerge simulation showed that the decreasing in storage capacity would cause higher stage and cause more serious risk especially for suburban region with lower elevation in all designed storm scenarios, and the response was most pronounced for a recurrence intervals equaling to 20 years. The research has rich theoretical research on stream structure in plain area, and provides decision-making and reference for flood management in the study area.