Author(s): Aksara Putthividhya; Sasin Jirasirirak; Pakkasem Thongchai
Linked Author(s):
Keywords: Rainfall-runoff; Runoff-sediment; Land use dynamics; Water balance; Sediment load; Double mass curve
Abstract: This research studies the land use dynamics and its effects on rainfall-runoff and runoff-sediment relationships in Yom river basin of Thailand. The study compares land use land coverage change (LULCC), rainfall -runoff pattern, and sediment load in the main river course from 1980s to 1990s and to 2014. A land use map updated from different periods (Land Development Department, Thailand) in combination with digital elevation model (DEM) and satellite imageries have been carried out as inputs for land use change coverage analysis. Double mass curve with trend curve analysis is employed to evaluate the effects of LULCC on rainfall-runoff and runoff-sediment yield relationships. The results indicate that from 1990 to 2014, many forests in Yom river basin have been significantly transformed into farmland and irrigation area, especially in high-slope locations relatively further away from the main river course. This change of land use pattern has consecutively altered the rainfall-runoff and runoff-sediment relationships, and lead to more pronounced slope of trend curve (STC) of annual rainfall-runoff and runoff-sediment mass curves in 1990s compared to 2000s, implying that more soil and water loss yield in 2000s. One can logically suggest that the runoff-sediment load obtained during 1990s is higher than 2000s with similar rainfall/runoff, which can further be explained by the historic landuse dynamics. With the new water allocation scheme for flood risk reduction in the lower Chaophraya river basin, agricultural practices have spatio-temporally changed and parts of Yom river basin have been used for flood retention areas, significant alteration in rainfall-runoff and runoff-sediment patterns has been observed (i.e., in Bangrakam and Kongkrailart Districts). Continuous reduction of forest fraction results in soil loss, landslide, river bank erosion, and flood occurrence results in a more degrading river water quality and potential decrease in river capacity for flood protection, all involved stakeholder such as local authorities, communities, farmers, and policy makers should pay attention to apply appropriate land use and watershed management and flood risk reduction practices.
Year: 2020