FLOOD ESTIMATION. IN SMALL CATCHMENTS

Abstract

Estimation of design flood for hydrologic design of various water resource structures, particularly for medium and major water resources schemes, has been one of the most active areas of research for the hydrologists and water resources engineers. Wherever it happens in either large or small catchment flood always bring harm to the society. Thus, estimation of design flood is very important component of planning, design and operation of water resources projects. There are various methods to estimate the flood. Some of them are Hydro Meteorological method or Synthetic Unit Hydrograph method, Statistical method or Flood Frequency method, Flood Formulae method, and Regional Flood Frequency method. The main problem in estimation of flood is the lack of data required for estimation. Synthetic Unit Hydrograph or Rational Method is used for flood estimation in catchments that have lack of data. In this study two study area are chosen for estimation of flood. The locations of study area are in India (Sub zone 3c Upper Narmada and Tapi sub zones) and in Indonesia (Jaya Pura). Central Water Commission (CWC) of Government of India has carried out extensive study on derivation of synthetic unit hydrographs for various regions in India, divided into 26 hydro meteorological homogeneous sub zones. In this study attempt has been made to compare representative UHfor Umar River with the synthetic UH derived for the Zone 3 (c) utilizing data for all the 18 bridge sites, and alternately and for 6 bridge sites which are near to Umar River. Assumption of hydro meteorological homogeneity becomes more realistic when only data of six sub basins is considered instead of using data of 18 sub basins which are widespread. In Indonesia flood especially in Jaya Pura occur in small areas. Due to the lack of data the calculation of flood estimation in ungauged small catchment usually using rational method or SUH Nakayasu method for develop synthetic unit hydrograph. SUH Nakayasu Method is more applicable in Indonesia for small rivers or for ungauged small catchment. In this study, catchment areas divide in 3 zone area according to geographic characteristic: zone I (hilly area without river) using rational method, zone II (plan area with a small river) using rational method and SUH Nakayasu method and zone Ill (hilly area with small rivers) is using SUHNakayasu method.