The Flat-Area Issue in Digital Elevation Models and Its Consequences for Rainfall-Runoff Modeling

When analyzing a digital elevation model, flat areas originating from the standard pit removal procedure can affect the characterization of flow paths and subsequent hydrologic or hydraulic analysis. In the present work, six case-study areas were selected, and two different methodologies for rainfall-runoff modeling were investigated within the framework of the Width Function Instantaneous Unit Hydrograph (WFIUH). One methodology is "standard," while the other is an "advanced" approach. The methodologies basically differ with regard to pit and flatarea treatment and flow-routing determination. In both approaches continuous rainfall-runoff modeling was applied and annual maximum hydrographs were compared. The results show that when using the "standard" approach a shorter WFIUH and a resultant hydrograph characterized by higher peak discharge and shorter duration are obtained.