Author(s): Abd Jalil Hassan, Norhan Abd Rahman, Sobri Haron, Tarmizi Ismail
Linked Author(s): Abd Jalil Hassan
Keywords: Runoff estimation, distributed model, time of concentration, flood modelling
Abstract: Runoff estimation depends on many factors and parameters which requires calibration. However, majority of catchments are ungauged and cause calibration to bea difficult task to achieve. Calibration is always required as standard practise but can be abused only to show a good match between observed and simulation. One issue which requires attention is that calibration should only be applied on paramater that cannot be measured prior to all measured data had been input correctly. Development of computer model that enables the combination of hydrologic and hydraulics component in a single model have changed the way flood analysis is carried out. However, the unguided use of model development could lead to the wrong way of modelling the hydrologic component which then leads to wrong estimation of runoff from the catchment. The Lumped model is very much similar to a black box model as it simplifies many parameters when converting rainfall into runoff. Parameters such as time of concentration (Tc), rainfall spatial distribution and landuse are lumped together as one input. This paper is about the development of hydrologic model by adopting a distributed hydrodynamic model. In this situation, the component of hydraulic mainly river channel and flood plain are introduced to the hydrologic model which shall reduce the dependency to various hydrologic parameters. Sg Ketil is one of the tributaries of Sg Muda Basin, Kedah which was used for the distributed model development. Three levels of hydrologic models were built to represent the catchment from one single catchment to one hundred fifty one subcatchment representing the tributeries using the readily available data from Department of Survey and Mapping Malaysia and landuse information from Google Map. Four method of Tc were tested and the simulations results show that the level III model give very similar runoff estimation regardless of the Tc method used. The flood plain was introduced to capture the storage effect. This results conclude that the distributed model which deployed the dynamic wave equation is able to reduce errors of the hydrologic model for computing runoff from subcatchment
Year: 2017