A GIS-assisted distributed watershed model for simulating flooding and inundation

A distributed watershed model combining kinematic wave routing, 1-D dynamic channel-flow routing, and 2-D diffusive overland-flow routing has been dev eloped to simulate flooding and inundation levels of large watersheds. The study watershed was linked to a GIS database and was divided into an upstre am mountainous area and a downstream alluvial plain. A kinematic wave routi ng was adopted at the mountainous area to compute the dlischarge flowing in to the alluvial plain. A 1-D dynamic channel routing solving the St. Venant equations by the Preissmann method was performed for the main channel of t he alluvial plain, whereas a 2-D overland-flow routing solving the diffusio n wave equation with the Alternating Direction Explicit scheme was used for floodplains. The above two routings were connected by weir-link discharge formula. The parameters in the model were calibrated and independently veri fied by single-event storms. An example application of flooding/inundation analysis was conducted for the Taichung station and the Woozi depot (Taiwan High Speed Rail). Suggested inundation-proofing measures - including raisi ng ground surface elevation of the station and depot and building a waterpr oofing exterior wall and their combination - were investigated. It was conc luded that building the waterproofing exterior wall had a strong tendency t o decrease peak inundation depth.