I would like to thank all of ...

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I would like to thank all of you for your valuable inputs. However, I have some words to say about Groynes and use of Vetiver grass as tools of erosion control. Erosion control of river Ganga requires both the application of mechanical/civil  engineering and ecosystem management. Hence, both application of Groynes and Vetiver system shall be required.

In the case of Ganga, considering current situation, control measures can be divided into two categories- corrective measure (i.e. in immediate need to control the erosion) and preventive measure (which will provide preventive control measure to protect both the river banks from erosion in future). The mechanical engineering solution (e.g. Groynes) shall fit in this corrective control measure category whereas the ecosystem based river management (e.g. Vetiver system) may fit into the preventive measure category.

Sharing some facts about lower stream of Ganga- the breadth of the river is approximately 25km at estuary and decreases to 6 km to the head end, with innumerable tidal bars, tidal island, mudflats, sandflats, coastal dunes, creeks, inlets and existence of mangrove forests at the estuary. Semi-diurnal tides are seen in this river and influence of tidal flows are felt up to 300km upwards from estuary. Tidal waves are so strong that they destroy even smaller boats. Tidal currents are relatively uniform while residual currents varies from 0.1 to 0.4 m/s. Annual sediment load is about 20 x 106 t (Mukhopadhyay,2007). Now the concern is whether Groynes system can work effectively in the lower stream of Ganga.

Use of Vetiver grass ( Chrysopogon zizanioid es) shall result into an effective solution for sure. Also, being an Indian species there is no fear of invasive species. Also Vetiver based river management has similarity to the Ganga management system (discussed in the discussion page). This system will work for sure but in the beginning a mechanical/civil engineering solution may be in need keeping in mind of urban structures and population pressure at the Ganga river banks.

Farakka barriage is one of the causes of sediment load in river Ganga. But the barrage cannot be dismantled because it will cause drying up of entire south Bengal including the megacity Calcutta (Kolkata).

A detailed modelling for erosion management  is very much required. Infact, what was discussed  in Ganga Management System (see discussion page), a detail streamwise (upper, middle, lower) aspect-impact analysis is required in the beginning.  

 

2 Comments

we all agree it is a Complicated  Problem.In 2000 I saw the Bhramaputhra is flowing about one Km. width in Arunanchalpradesh but the next year the river is following in another way .The people are suffering Like this the erosion will change the ROUTE of River Ganga. Here one easy way is to INTERLINKING THE RIVER GANGA to other rivers and reduce the STRENGTH of FLOW in all times in summer and Rainy season this will give FERTILE to 98 Districts of DROUGHT DISTRICTS of INDIA.The river banks can be protected any way we have to safe guard the FLOW of River GANGA.If it Changes the route every thing is in waste .SO years study and How many times it Changed and where the EROSION is happening more CONDUCT study,Research and ONLY start For a solution.

The Dredging to deepen the river,Making islands, cultivating VETIVER grass ,Steel guarding to Banks are depending upon the FLOW OF RIVER.An apt decision to Protect the Life valuables of Human beings is needed.

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I agree, it is really complicated to find one solution for a river with 25 km width. It has to be multiple solutions. It is possible to have one solution per location. There are many measures used before and now as mentioned here asap. In my mine this the steps which  might be considered:

Modelling of the hydrodynamic and morphodynamic behaviour of this river.

Classify the erodible locations in the river. For instance the hydrodynamic conditions and the soil characteristics.

Apply all the possible measures to see their effects. Measures like groynes, fixed layer, sediment nourishment, and sediment dredging and bank revetment. It is important to know how to design the measure like the length and the angle of a groyne for instance at a certain location.

Evaluate the measures per location socially, economically and environmentally

The non-structural measures have to follow the same track.

Eventually, you may mitigate the bank erosion in some locations, eliminate it from other locations and makes the bank erosion in totally new locations. The cycle is on and on…sustainability. And definitely the situation will be better than now and proactive approach “early warning system of bank erosion” will be under operation .

But they need to start, the journey towards sustainable river management starts from  a comprehensive study and well knowledge to the system

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