Impacts of Land cover changes on rainfall-runoff and sediment transport processes in the Kelani River, Sri Lanka

Dissanayaka Mudiyanselage Pavithra Sudeshika*, Yoshiyuki Imamura, Daisuke Harada, Shinji Egashira

Abstract

The present study examines the impacts of land use change on rainfall-runoff, and sediment transportation together with occurrences of landslides in the Kelani River Basin, using MODIS Global yearly land cover data, a physically based distributed rainfall-sediment-runoff model, and a sediment erodibility/ landslide index model. It was realized that the predominant land-use types within the basin were identified as woody savannas, forest, cropland, and built-up areas, and the forest area decreased by 15% and 8.3% of the total basin in 2010 and 2022, respectively, compared to 2001. These alterations in land use correspond to changes in the peak flow discharge and sediment transport rates. This study highlights that the sediment hydrograph changes more sensitively compared to the changes in the flood hydrograph caused by land cover alterations, as the bedload rate is proportional to flow discharge raised to the power of 3/2.

Keywords: MODIS land cover, rainfall-sediment-runoff model, Sediment transport rates, flood flow

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