Long-term sediment pattern of Selangor River Basin, Malaysia Impacted by land use and climate changes

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Siti Nurhidayu Abu Bakar, Mohamad Azhar Mohamad Zin, Mohammad Faizalhakim Ahmad Safuan

Friday 3 july 2015

11:15 - 11:30h at South America (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) Basin-wide sediment management

Parallel session: 15J. Sediment - Basin

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Rapid development (urbanisation and land use conversion) and climate change (Southern Oscillation) accelerates sediment production in an impacted tropical river basin. The land use changes data from the most developed river basin, Selangor River Basin (SRB) in Malaysia together with rainfall records from an adjacent hydrological station and Southern Oscillation Index (SOI) were used to describe the long term sediment pattern. The highest annual mean sediment were recorded at Rantau Panjang (1976-2008; 1450 km2) was in 14.58t/ha/year in 2006 (SOI=+0.3) whereas of 0.0154t/ha/year at Rasa (1978-2000; 321km2) in 1981 (SOI=+1.8). The lowest of both catchments were observed in 1998 and 2000, respectively of 0.0016 (SOI=-1.1) and 0.0004 t/ha/year (SOI+7.8), respectively. The Rasa catchment mostly converted to tin mining (9185ha in 1997) and 600ha of Selangor Dam was constructed in 1999 to 2005 which involve vegetation clearance which might increase the sediment from the basin. The sediment record for SRB was escalated starting from 1991 onwards might be resulted from urbanization and land opening for oil palm plantation within the basin. The relationship between sediment and land use change showed that the decreasing of forest area (-82.7%) and increasing of oil palm area (+551.6%) from 1966 to 1997 had a great impact to the basin sediment with R values of 0.732 and 0.867, respectively. The increasing of newly cleared area (+215.9%) and urbanisation (+494.8%) from 1966 to 1997 within SRB resulted fluctuation in annual mean sediment for both stations (R=1.000 and 0.734, respectively). The results indicated the sediment pattern for SRB was not largely influenced by SOI (R=0.2147) or total annual rainfall (R=0.1911) but largely impacted by land use conversion. More effective land use planning method by considering the impacts of accelerated sediment from converted land use is needed in ensure environmental protection in the developed river basin for sustainable development.