Hydrology Model for Determination on the Flood Index Based Analysis of Flood Discharge for Asahan River Management

Asahan river is a river whose headwaters of Lake Toba and flow into the waterway whose length is approximately 147 km. The existence of Asahan river as part of the hydrologic system becomes a very important thing to be kept. Frequent flooding in Asahan river is one hydrological events. This paper proposes a form of hydrology model for determination on the flood index based analysis of flood discharge. Secondary data include data from relevant agencies such as rainfall data, flow data, land use data, and then analyzed with Gumbel and log Pearson method . Furthermore, the calculation of flood discharge using Rational method, Nakayasu, and flooding in the downstream surface calculation also uses a combination of methods HEC-RAS. The main purpose of this paper is to produce a model of hydrology flood index determination that can be used as a benchmark would be flooding and manage sustainable Asahan river. Inundation in the downstream area index average of 0.32 and an index obtained in downstream flooding average obtained at 0.52. With hydrological modeling based index flood discharge in Asahan river against rainfall and land can be mapped if there was a flood in the region.