Interaction of Spatio-Temporal Resolution of Rainfall Observations and a Semi-Distributed Runoff Model for Flood Forecasting: A Case Study from Dallas Fort Worth Region

This study examinesthe interplay of the spatial-temporal resolutions of radar rainfall observations and a runoff model for flood forecasting, specifically for the CASA Dallas Fort Worth (DFW) test-bed. ModClark model developed by HEC (Hydrologic Engineering Center in US Army Corps of Engineers) is used to apply QPE radar rainfall data (Peters and Easton 1996; HEC 1996; Kull and Feldman 1998). The contents of this study are as follows. Firstly, this study examines an effect of spatial resolutions of the runoff model on flood forecasting. In the process of effective rainfall in a distributed runoff model, grid sizes of the runoff model affects simulation results because parameters related to the model are estimated from topographical data which have spatial resolution for each grid. In case of ModClark used to maps such as land-use and soil for estimating the runoff curve number of SCS (Soil Conservation Service) method as the parameter for each grid, the parameter tends to decrease when grid size is increasing. Thus, the examination is necessary to find the quantitative magnitude of the effect on flood forecasting. Secondly, an effect of the spatial resolutions of rainfall input data was examined. There is the smearing effect on the rainfall amount when the grid size of radar rainfall is relatively increasing. The effect generates a relative error arising from different grid sizes for radar rainfall, and it will lead to error in runoff simulation results. Lastly, this study examines an effect of spatial-temporal resolutions of radar rainfall observations and the runoff model depending on the watershed scale on the flood forecasting. For this topic, various scales of watersheds were applied to two topics above mentioned. Also, this research examines the interplay of the spatial-temporal resolutions of radar rainfall observations and the runoff model. To study these three topics, this research was done over the Fort-Worth area in Texas as part of the CASA DFW test-bed.Scale range of areas from 92to 328 sq. kmwas used. 0.5~10.0 km was considered as the spatial resolutions of radar rainfall data and ModClark model. This study applied temporal resolutions were studied from 1 to 60 minutes.