A successful water resource management consists of a better provision for flood control and the water quality issues, and the investigation of the influence of riverside structures and dam by analyzing the climate, river, water quality alteration. A mathematical model is provided for the analysis of water resource having great variability, and its influence should be predicted before. Therefore, the loss process of rainfall evaporation, runoff, infiltration, and atmospheric cycle, subsurface water vegetation, and soil moisture have to be taken in consideration.
The hydro meteorological data and the overland data are needed for carrying out the rainfall-runoff model. The overland data are fundamentally controlled by the overland flow system. As published in the grid-based distributed rainfall-runoff model and the previous research’s results, the selection policy of roughness factor is the most sensitive parameter in runoff response, and influences directly the arithmetic model results.
This research work investigates specific parameters of vegetation influencing directly the rainfall-runoff model simulation results. Besides, the vegetation heterogeneity impact on the rainfall-runoff model results is treated as well. Useful guidelines, giving methods to select the average of vegetation heterogeneity, are expected herein.
In this research, the basin area is about 930, and the total area is of 1,164. The investigations are carried out on the rainfall-runoff model for the Yongdam dam basin which is in the upstream area of Geum river basin located between 36° 00‘ ~ 35° 55’ north latitude, 127° 20‘ ~ 127° 45’ east longitude. With the grid-based physical model developed at Colorado University in the United States, the FLO-2D model that is capable of clarifying flood-runoff hydrograph and rainfall-runoff curve on the overland and inside stream channel was performed.
For performing rainfall-runoff model, the meteorological data have been taken from 8 rainfall stations for Yongdam dam basin, whereas the overland data were taken from 3 different institutions. The medium classification of land covering map with the scale of 1:25000 was made by the Ministry of Environment, the sea map data of a 5m dam was taken from National Geographic Information Institute, and the Ministry of Land, Infrastructure and Transport. The data of detailed soil map with the scale of 1:25000 was taken from the Ministry of Construction and National Institute of Agricultural Science and Technology.
While performing the rainfall-runoff model, the FLO-2D grid size was set to 50m, the map dimensions were established as follow: width = 45.6km, length = 60.6km, area = 2700 , and the grid number was 1105344. A grid of the established FLO-2D model will contain every 100 data in 5m on the land covering map data. One hundred data of overland characteristics are applied in one grid of the FLO-2D, when it comes to determining the parameters, each of the following methods were applied. The arithmetic average, integrated average and predominant average methods were carried out. Using the results of the overland characteristics found from each of these methods, the vegetation parameters were determined. Then after, these parameters were applied in the FLO-2D model, and when the results of the observed water flow were compared, excellent result came out from the integrated average method. Due to the variation in scale, based on the physical theory of the integrated average method which improves the numerical model about expressing vegetation in terms of determining the representative value of its heterogeneity, the integrated mean method was decided to be useful.