Giha Lee

Interaction between Topographic and Process Parameters due to the Spatial Resolution of DEMs in Distributed Rainfall-Runoff Modeling

Selecting an appropriate digital elevation model (DEM) resolution is an essential part of distributed rainfall-runoff modeling since the resolution affects parameter values and, in turn, leads to predictive uncertainty. Moreover, the DEM resolution directly determines the computational workload required for model simulation. This study conducted several experiments to clarify the interaction between topographic and process parameters due to the spatial resolution of DEMs in distributed rainfall-runoff modeling. First, five different spatial resolutions (from 50 m to 1 km) were used to analyze the effects of DEM resolution on the topographic and process parameters of a distributed rainfall-runoff model [kinematic wave method for subsurface and surface runoff (KWMSS)]. Second, parameter compatibility was tested with regard to the sensitivity of model performance to optimal parameter values for each DEM, by applying the best-performing parameter combinations for each resolution to the models based on differi...

Comparative Analysis of Geomorphologic Characteristics of DEM-Based Drainage Networks

Identifying the optimal drainage network based on digital elevation models (DEMs) is a fundamental task in rainfall-runoff modeling. Rapidly improving geographic information system technology enables hydrologists to use a variety of DEM-based hydrologic models that yield spatially concrete outputs. However, reliable drainage networks are still difficult to represent due to insufficient information about the dynamic behavior of water movement on catchment hillslopes. This study proposes an efficient method for drainage network identification through a comparative analysis of geomorphologic characteristics, such as drainage density, length of hillslope flow path, source area, etc., using area threshold and slope-area threshold criteria that incorporate scaling properties between the local slope and the contributing area. The results demonstrate that both criteria yield different drainage networks from “blue lines” based on topographic map from the Korean National Geographic Information Institute. Although t...

Estimation of the Nash Model Parameters Based on the Concept of Geomorphologic Dispersion

This study presents a new method to estimate the Nash model parameters on the basis of the concept of geomorphologic dispersion stemming from spatial heterogeneity of flow paths within a catchment. The proposed method is formulated by including physically meaningful characteristic velocities for channel and hillslope and also takes account of the effect of complex interactions between channel and hillslope hydrological behaviors on catchment responses. We applied the proposed formulas to the Bocheong watershed, an experimental area established under the International Hydrological Programme (IHP) in Korea, with several storm events to assess the individual effect of channel and hillslope on hydrological responses in the study site. The characteristic velocities were estimated by topographic data based on a 20×20  m digital elevation model (DEM) from a 1∶25000-scaled topographic map and statistical features of the historical events. We then calculated the Nash model parameters by substituting the estimated ...