Case Studies

Bank Protection work and Flood Control measure for Madhumati and Bonar Nallah

Techfab India Industries Ltd
Bandipora District @ 60 km from Srinagar

In 2015, Both Nallah had experienced severe bank erosion due to melting of ice at high altitude and release of water from the Kisha ganga Hydro Electric Power Project (KGHEP).

In 2015, Both Nallah had experienced severe bank erosion due to melting of ice at high altitude and release of water from the Kisha ganga Hydro Electric Power Project (KGHEP).

Bank Protection work and Flood Control measure for Madhumati and Bonar Nallah

Introduction

The work was extremely challenging in terms taking material to site due to steep gradient, high water level & surrounded by locality. The temporary access road was constructed & water from nallah was diverted to facilitate gabion work. The gabions were placed in situ by varying foundation depth 1m to 3m. We have given extensive training for proper implementation of gabion at site. The contractor started the work simultaneously at various locations due to its urgency and timeline fixed in the contract. The series of gabion retaining wall: spur & energy dissipater were being constructed along Bonar & Madhumati Nallah.

The work was extremely challenging in terms taking material to site due to steep gradient, high water level & surrounded by locality..

Problem Description

This region is surrounded by high slope mountain and due to steep gradient, the velocity of water is quite high causing erosion of the bank and bed of the channel. It is observed that there is erosion at various location along the nallah thus posing threat to the community staying along the banks.

Solution Proposed

The advantage of Gabion wall & other form of energy conservative structures was adopted for it’s easy construction; economy & flexibility. The gabion structures go easy with surrounding & maintain ecological balance by allowing growth of flora and fauna of the regime.

 The permeable nature of the Metal Gabion eliminates buildup of hydrostatic pressure behind the retaining structure and uplifts caused by turbulent flows.

The flexibility of the double twisted hexagonal mesh helps in withstanding differential settlement without fracturing the structure particularly when a structure is installed on unstable and uneven ground or in an area where scours from waves or current can undermine.

Metal Gabion structures are heavy monolithic gravity units able to withstand earth's thrust. Its efficiency increases instead of decreasing with age since further consolidation takes place as silt and soil collect on the voids and vegetation establishes itself

Execution On Site

• Setting out the area as per drawing • Mobilisation of Geotextilebags and soil to the project site. • The excavated soilwas disposed of by tippers to a suitable distance from bank side to reduce overburden of bank. • The slope formation was done with necessary ramming to remove any undulations and corrected to the desired slope before laying nonwoven geotextile. • The geotextile was laid across the dressed slope over which sand filled geotextile bags were placed. • The bags were filled with locally available River Sand; the sand used as filling was as per technical specification of the project. • After sand filling was completed, the geotextile bag was weighed to confirm the desired weight as per technical requirement. • After confirmation of weight, bag wasstitched by special hand held stitching machine. • For the convenience bags were stored in batches or any suitable multiples as per available space at site. • The dumping/laying of geotextile bags for launching apron was carried out when river was dry or with the help of small boats to complete the activity on time. • Laying of bags was done under supervision of the site in charge.Laying work was inspected time to timeby authority. • Laying of porcupine concrete element was carried out as per drawings and installation guidelines for spur construction.

CONCLUSIONS

It is observed that Completed Geotextilebags structure withstood recent flood of 2019 without any major damage of the properties, loss of land and without loss of any cattle or people.The protection is serving as desired by the authority., It is also observed that the river has changed its course @ 9-10 m from its existing flow profile and deposition of the sand at multiple locations.

Related Products

TechFab Metal Gabion