Controlling Riverbank Erosion with Jute Geotextiles
Rivers flowing across unconsolidated terrain are susceptible to erosion of the banks in their effort to find the most convenient course. Besides, erodibility of bank soil and fluctuation of water level contribute largely to bank erosion. This chapter elab
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Controlling Riverbank Erosion with Jute Geotextiles
Abstract Rivers flowing across unconsolidated terrain are susceptible to erosion of the banks in their effort to find the most convenient course. Besides, erodibility of bank soil and fluctuation of water level contribute largely to bank erosion. This chapter elaborates technical as well as economical advantages of using treated Jute Geotextiles (JGT) over the conventional granular filter for controlling riverbank erosion. The perception of low effective life of JGT and its assumed ineffectiveness in riverbank erosion control has been countered with reasons. The chapter explains the elements of design with focus on aspects of soil retention, permeability, and transmissivity of JGT and clogging. Parameters for design of riprap overlying JGT have also been indicated. Installation procedure of JGT has been explained with sketches. Keywords Granular filter • Erodibility of bank soil • Soil tightness • Unidirectional flow • Hydraulic conductivity of bank soil • Coefficient of uniformity • Gradient ratio test • Hydraulic conductivity ratio test • Riprap • AOS of JGT
Bank erosion is a common phenomenon in rivers flowing through areas that are yet to attain stability from geological and geotechnical considerations. The GangaBrahmaputra delta (West Bengal, Assam, Bangladesh) is one such region which has grown on alluvial deposition. Before deciding on the remedial measure, it is important to ascertain the causes(s) of erosion. High velocity of flow hugging the bank and exerting a tractive force on it, vortices at the toe of the bank, waves induced by wind and big vessels on move, large fluctuation in water level, and erosion proneness (erodibility) of bank soil are the contributory factors to bank erosion. Rivers moving along unsettled terrain often follow tortuous courses developing meanders of varying sinuosity in their attempt to follow the most “convenient” course. The concave end of any meander is prone to erosion, while the convex end on its opposite experiences accretion of sediment. The process of meandering of a river is complex. We desist from elaborating the causes here. Understandably mere bank protective measures may not provide a long-term solution in cases where the influencing parameters causing erosion are several and variable. In such cases there is need to adopt appropriate structural measures such as spurs, apron, and the like for counteracting the erosive forces of a river in © Springer Science+Business Media Singapore 2017 T. Sanyal, Jute Geotextiles and their Applications in Civil Engineering, Developments in Geotechnical Engineering, DOI 10.1007/978-981-10-1932-6_7
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7 Controlling Riverbank Erosion with Jute Geotextiles
conjunction with bank protective measures. For instance repelling spurs can push the direction of flow away from the bank, submerged spurs can neutralize the vortices near the bank toe, and apron can reduce the chances of bank-toe collapse. In majority of the cases of localized riverbank erosion, the prime cause of bank er
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