Geomorphology and Hydrology of 2014 Kelantan Flood

Abstract

The December 2014 Kelantan floods were the worst on records in terms of depth and extent of inundation as well as damages to properties and infrastructure. Therefore, a comprehensive and integrated flood monitoring, forecasting, and warning methods are needed to allow planning of responses to potential future floods by the government and related environmental agencies. The Kelantan state has been affected by floods every year in modern times. Meteorological and hydrological records have shown that the Kelantan River often overflows during the NE monsoon season. This preliminary due to heavy rainfall, causing an almost annual recurrence of floods to the state between the end of November till March (DID 2014/2015). Excessive land use changes such as deforestation (i.e. logging and clearing for agriculture) and increased precipitation intensity and frequency are the possible causes for this change. However, little research has been conducted to understand and quantify how these factors contribute to changes in the magnitude and frequency of flooding in the area. This research will attempt to integrate geomorphological, hydrological and meteorological data and evaluate their impact on the recurrence of the annual flood in Kelantan. The main objective of this research project is to study all factors that contribute to the flooding events in Kelantan and propose a strategy to minimize the impact of future flooding events. The methodology planned to achieve the specific objectives for this research comprises of: (i) analysis of satellite imagery and remote sensing images to map general geomorphology of Kelantan; (ii) analysis of medium-term climatic data (temperature and rainfall data) to evaluate the impact of hydrology on the flooding events. From the Digital Elevation Model (DEM) map, the geomorphology of Kelantan can be clearly seen where at the southern part of Kelantan (Gua Musang and Kuala Krai area) is more hilly and highly elevated, and toward northern parts of Kelantan which cover area Kota Bharu, Pasir Puteh, Tumpat, Bachok, Pasir Mas, Tanah Merah, the elevation more gentle since it near to coastal region area. This lowland geomorphology allows becoming an escape route for the water and later transported to the nearby delta before escaping to the sea which is the main basin. The fluvial geomorphology at the Kelantan Delta area is meandering since it located at downstream area. More than that, the urbanization aggressively increases at floodplain area and also forces the flooding to occur. Meanwhile the data could also identify the water flow from rivers in southern upstream highland region (Lebir River and Galas River) to Kelantan Delta area. The existence of bottle necks in southern parts of Kelantan area such as Dabong, Manek Urai, and Kuala Krai can be identified under the image whereby the river flows through a narrow or obstructed section from catchment area. It could assist to decelerate the water flow to Kelantan River in the event of flood and long duration rainfall. However, river-bottle neck will accelerate the rise of flood level in southern upstream highland area. The Kelantan River Basin experiences the northeast (NE) monsoon climate which is responsible for the heavy rains that hits the east coast of the Peninsular Malaysia, such as the state of Kelantan, Terengganu, and Pahang, and frequently cause overflow of riverbank flooding. The flooding that occurred in 2014/2015 was caused by heavy rains brought by the northeast monsoon winds blown from November to March. Floods in 2014 showed the total rainfall in rural areas is more dense (>60 mm) than the coastal areas (DID 2014/2015). Heavy rain began to fall in the Gunung Gagau on December 16, 2014, in which a total of 6648.0 mm in the coastal areas have been covered by 6 new stations in Kota Bharu, Tumpat, Pasir Mas, Machang, Bachok, and Pasir Puteh while in rural areas of 7373.0 mm, which also includes 6 stations, namely Dabong, Jeli, Gua Musang, Laloh, Aring and Gunung Gagau for the month of December. Continuous heavy rains until early January as recorded stations involved. Based on the preliminary geomorphological and hydrological analysis, DEM and satellite data, future development plan of residential areas, reforestation and plantation, town planning, and river engineering projects for Kelantan state should incorporate the details of the studies. Several flood management strategies are proposed here. In the southern upstream areas, desilting of the river system needs to be carried out. The deforestation projects should be stopped in the areas which forms large rainfall catchment areas. The logging activities should be limited to non-catchment, intermediate, and lowland areas. In the lowland, Kelantan delta areas, urbanization and river engineering projects need to be re-evaluated. Construction of large monsoon drains may help to distribute the floodwaters more efficiently.