Author(s): U. De S. Jayawardena
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Abstract: The land surface is reducing due to the processes of weathering and erosion and transportation either by naturally or man made. The separated materials or sediments are deposited in the lower basins or joins with the sea sediments. This river sedimentation may be high in tropical countries because rock weathering is most intense in the humid region. Sri Lanka is a country in the tropical region and therefore the rate of weathering may be high comparatively. Hence a study on the rock weathering, river sedimentation and landscape reduction in Sri lanka are very important. The objective of this basic research is to find out the weight losses and the rate of the landscape reduction with the increase of weathering and erosion in Sri Lankan rocks. About 300 samples from 72 locations were used to find out the bulk density and porosity of fresh and weathered rocks. The results show the decrease of bulk density and the increase of porosity with the increase of weathering. The reduction of bulk density of rocks indicated that total loss of material is about 20% by weight. The total dissolved ions and total suspended materials in surface waters are a result of the chemical weathering of rocks in the entire region of the river basin. The available data on the runoff of the total river basins in Sri Lanka and chemical analysis of river waters in different localities were collected from the various references. The calculation of total dissolved solids and total suspended solids in the river waters of the entire country indicates the average rate of landscape reduction is about44mm per 1,000 years period.
Year: 2004