Logo South Asian Disaster Knowledge Network
Site Search Google   GO
Bullet Flood
Home » Hydro Meterological Disasters » Flood

Structural Measures

This has been one of the major structural approach in which the river is restricted to its existing course and prevented from overflowing the banks. Usually embankments are constructed with earth but at some places masonry and concrete walls are also used. However what is important is to note here that embankments are designed to provide a degree of protection against flood of a certain frequency and intensity or a maximum recorded flood depending on the location and economic justification.
During recent times, divergent views have emerged concerning effectiveness of embankment. While there are serious concerns over their usefulness over a long time frame, there have also been arguments in favor such as providing only road communication during flood seasons and shelter in low lying areas. Studies on effectiveness of embankments conducted around the world, have pointed out some of the problems such as poor congestion in protected areas, silting of rivers which not only means rising river bed level and consequent decrease in carrying capacity but also depriving neighboring agricultural land from fertile soil and ground water recharge. There have also been concerns on the issue of embankment capacity to withstand erosion.

Dams, Reservoirs and other Water Storage Mechanism
Basically Dams, reservoirs and other such water storage mechanism store excess flood water that can be released after flood threat has receded. This also helps in use of such stored water for irrigation, power generation and meeting drinking water, industrial needs.

Channel Improvements
The aim of Channel Improvements is to increase the area of flow or velocity of flow or both to increase carrying capacity. Normally this measure involves high cost and there are also problems of topographical constraints to execute such a measure.

De-silting and Dredging of Rivers
The de silting approach is still to be perfected in the sense that various committees and expert groups appointed by Government of India are yet to recommend this measure as an effective mitigation strategy. However selective de silting and dredging of rivers at outfalls/confluences or local reaches can be adopted.

Drainage Improvement
This aims at construction of new channels or improving capacity of existing channels to decongest and prevent flooding. However what is important is to ensure that such an approach do not cause congestion and flooding in downstream area.

Diversion of Flood Water
This involves diverting all or part of flood water into a natural or artificial constructed channels which may be within or outside the flood plain. The diverted water may or may not be returned to the river at a down stream. Usually effective to prevent flooding around cities, the flood spill channel for Srinagar and the supplementary drain in Delhi are examples of this approach.

Catchments Area Treatment
The aim in this approach is to provide protection to catchments areas through measures such as afforestation which minimize siltation of reservoirs and silt load in the rivers. This can be a very useful approach to control flood peaks and suddenness of run offs.

Sea Walls/Coastal Protection Works
The construction of Sea walls and other such work try to prevent flooding from Sea water. These are highly cost intensive apart from the fact that complexity of sea behavior and other environmental aspects should also be considered.

Non-Structural Measures

Flood Plain Zoning
The basic idea here is to regulate land use in the flood plain in order to restrict the damages. It aims at determining location and extent of areas for developmental activities so that damage is minimized. It lays down guidelines for various type of development so that adequate mitigation is built for the worst flood scenario. There can be different consideration for preparing flood plain zoning for example, one can locate parks, playgrounds etc. for area which have a up to 10 year frequency while prohibiting residential colonies, industries etc. and allowing residential and other public utilities with specific design guidelines in areas which have a 25 year frequency.

Flood Forecasting and Warning
A nationwide flood forecasting and warning system is developed by Central Water Commission (CWC) and this initiative has also been supplemented by states who make special arrangements for strategically important locations in their states. The forecasts can be of different types such as forecast for water level (stage forecast), discharge (flow forecast) and area to be submerged (inundation forecast). The forecast when carries definite risk information is called warning. The flood forecasting services involve collection of hydrological data (gauge, discharge), meteorological data such as rainfall.

Flood Proofing
These are measures designed to minimize the impact when flood water comes such as raised platform for shelter to population, cattle etc., raised platform for drinking water hand pumps, bore wells above flood level, house/building architecture, provision for relocating vial installation such as communication, power etc.

Weekly Disaster Updates
Software Developed by Tata Consultancy Services Limited. Copyright © 2009 SADKN, All Rights Reserved                     
  Concurrent Users:
Number of hits: