EIACP (PC-RP) on Environmental Problems of Mining

River Sand Inflow Assessment and Optimal Sand Mining Policy Development

Binoy Aliyas Mattamana¹, Shiney Varghese², Kichu Paul³

^1,2Professor, ³Assistant Professor, M.A. College of Engineering, Civil Engineering Department, Kothamangalam, Kerala, India

Abstract— The indiscriminate and unscientific sand mining has become a serious environmental threat to the river systems of Kerala. The present study focuses on the determination of sand inflow in different stretches of the Periyar River and thereby optimizing the sand removal by considering several socio-economic and topographical features. For the determination of this sand inflow, an analytical method using Bed Load Transport model is used. Among the different Bed load transport models, The Mayer- Peter’s Formula is used in the present study. For this, the sample of sand from different critical locations, flow data, and other river characteristics were used. The values of different parameters in the model are calculated using lab and field test results and also with data collected. The model is applied for 22 years from 1983 to 2004. An average of the rate is taken as the daily rate of sediment transport for different months. Considering several uncertainties associated, the sand inflow is calculated which is then converted into Truck Loads Per Day (tlpd). An equilibrium policy is adopted to determine the optimal amount of removable sand. If the sand removal is done in accordance with the sand inflow, then the river can attain a steady bed profile. For this, the study area is divided into five stretches on the basis of topographical and geographical differences and also with change in grain size of sand. The minimum sand inflow, from the various kadavus of the stretch is taken as the monthly inflow in that particular stretch. In order to compensate the past indiscriminate mining practices, 50% of the minimum sand inflow is used for replenishment and is equally distributed to other months. The amount after replenishment is added with this extra amount of sand. This value is taken as the optimal amount of removable sand from each stretch. Dividing this value with the number of existing kadavus in the region, the optimal amount of mineable sand from each kadavu is obtained.

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