Flood causes due to some geological aspect : a case study in Kota Bharu, Kelantan, Malaysia.

Floods are a natural phenomenon that occur when a great flow of water into the river overflows the river banks and floods the nearby land. Floods in the study area were mainly caused by heavy rainfall brought by the Northeast Monsoon, and were also affected by several factors such as the engineering and structure of the drainage system also town planning management. Geological factors also contribute to flooding, and aspects studied in this research were sediment in the river, geomorphology of the river banks and the infiltration rate of the ground soil. In order to reduce the risk of flooding, a method to enhance the efficiency of the process for evacuation during the flood event needs to be created and priority must be focused on high risk areas. But until now, a specific evacuation model was not available. Hence, the research objectives were to determine the causes of flooding from hydrological and geological aspects and to produce a flood hazard map. The two parameters used to study the sediment in the river were turbidity and total suspended solid. Software Envi, Erdas and ArcGIS were used for river geomorphology analysis of satellite images. Particle size distribution analysis and double ring field test were used to determine the permeability of the study area. As a result, turbidity results after flood increased six times compared to before flood while total suspended solid results after flood increased 1.5 times compared to before flood. Analysis of the geomorphology of the Kelantan River banks shows geomorphological processes have extensively occurred and modified the river pattern, while infiltration analysis of ground soil shows that 70% of the area was categorized as low permeability, 15% as moderate to high permeability and 5% as very high permeability. A flood hazard map was produced by using ArcGIS version 10 where 217.41 km2 of the study area was categorized as low hazard, 137.22 km2 as medium hazard, and 47.14 km2 as high hazard. This study shows that effective mitigation measures should be planned in order to reduce the risk of flooding, which will also reduce the loss to people living in the study area and enhance their standard of living.