Study on the performance of geobags as an alternative approach to river bank and bed protection

Abstract

In order to prevent or minimize the loss of valuable land, several stretches of the river banks might need suitable protection against erosion. So the design of protection structures requires suitable methods and materials to mitigate erosion. Usually in many protective works, stones, rocks or c.c. blocks are used in the past. Bangladesh lacks stones, bank protection works with concrete blocks and stones are expensive to build and maintain. So it is required to explore an alternative low cost material to serve the purpose. At present, a new technique with sand filled geobags is being used to protect the bank and bed in many projects. Commonly sand filled geobags are used in emergencies but not for long lasting and large scale bank protection. Now these are used as a stable protective element. But very limited investigations were carried out to evaluate the performance of geobags as a protective measure for erosion in Bangladesh. Considering the above viewpoint, the present study has been undertaken to study the perfonnance of geobags as bank and bed protection material. Protective works which have recently been implemented at Pabna, Chandpur, Rajshahi and Faridpur were chosen to be visited for this study. Based on collected field data and observation, present conditions of the works have been analyzed. Sizes of the C.C. blocks, stones have been determined by applying commonly used formulas and those were compared with the sizes actU<lllyprovided in the field for a given project. Adequacies of blocks in terms of size and weight have also been assessed following this procedure. Results found from different analysis and field observations to analyze the performance of geobags are very good. Geobags have been identified as effective, appropriate, adequate and sustainable protective material against erosion at the projects of Pabna, Chandpur, Rajshahi and Faridpur. Also the sizes of the slope protection materials and quantities of the works have been found satisfactory. Although, the overall performances of the stability of geobags need more time to analyze, geobags are identified as cost effective, available, easily movable and suitable material for bank protection works in Bangladesh.