GENERATING DESIGN HYDROGRAPHS BY DEM ASSISTED GEOMORPHIC RUNOFF SIMULATION - A CASE-STUDY

The geomorphic instantaneous unit hydrograph (GIUH) may be one of the most successful methodologies for predicting flow characteristics in u ngauged watersheds. However, one difficulty in applying the GIUH model is determination of travel time, and the other difficulty is the larg e amount of geomorphologic information required in the study watershed . Recently, using the kinematic-wave theory, Lee and Yen (1997) have a nalytically determined the travel times for overland and channel flows in watersheds. The limitation of using an empirical velocity equation to estimate the runoff travel time for a specified watershed is then relaxed. To simplify the time-consuming work involved in geomorphic pa rameter measurement on topographic maps, the GIUH model is linked with geographic information systems to obtain geomorphic parameters from d igital elevation models. In this paper, a case study performed for pea k flow analysis in an ungauged watershed is presented. The geomorphic characteristics of the study watershed were analyzed using a digital e levation model and were used to construct the runoff simulation model. The design storm was then applied to the geomorphic runoff simulation model to obtain the design hydrograph. The analytical procedures prop osed in this study can provide a convenient way for hydrologists to es timate hydrograph characteristics based on limited hydrologic informat ion.