Flood Management control methods ,Causes , issues.

 What is Flood Management and it's Control Methods?

Flood control methods are used to reduce or prevent the detrimental effects of flood waters. Flood relief methods are used to reduce the effects of flood waters or high water levels.

This manuscript aims to present the international experience in control and management of floods, in order to identify the best practices. In this study, the causes and consequences of the floods, the measures used to control them, the procedures adopted to guarantee the safety of the post-flood cleaning will be presented and the measures to deal with future floods will be outlined. This article is intended, fundamentally, to offer its readers the knowledge on the best practices of control and management of floods around the world.

Keywords

Floods; Flood control; Flood management.

Highlights

► Flooding is the most devastating natural hazard in Pakistan. ► Flood characteristics in all three main basins vary to a considerable extent. ► A setup consisting of organizations, legislation, and measures is implemented. ► The increased vulnerability of the country was disclosed during flood in 2010. ► A risk-based, pro-active, and self-supporting approach is recommended.

Causes of Floods

Floods are caused by many factors: heavy precipitation, severe winds over water, unusual high tides, tsunamis, or failure of dams, levels, retention ponds, or other structures that contained the water.

Periodic floods occur on many rivers, forming a surrounding region known as the flood plain.

During times of rain or snow, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation, some evaporates, and the rest travels over the land as surface runoff. Floods occur when ponds, lakes, riverbeds, soil, and vegetation cannot absorb all the water. Water then runs off the land in quantities that cannot be carried within stream channels or retained in natural ponds, lakes, and man-made reservoirs. About 30 percent of all precipitation is in the form of runoff small and that amount might be increased by water from melting snow. River flooding is often caused by heavy rain, sometimes increased by melting snow. A flooding that rises rapidly, with little or no advance warning, is called a flash flood. Flash floods usually result from intense rainfall over a relatively small area, or if the area was already saturated from previous precipitation.

Flood Management Issues

Flood management is often in conflict with water supply practices and needs. Flood control managers must keep enough reservoir storage space available to manage floods during heavy precipitation, but water suppliers focus on storing enough water to protect against drought.

Additionally, flood control involves many different local, state and federal agencies [see list at bottom of the page], and their management philosophies change with the political and economic times. The state also has many local flood management agencies responsible for the day-to-day operations and maintenance of facilities, development and implementation of flood management and stormwater drainage plans, and coordination with other state and federal agencies.

Flood management methods. 

Steps can be taken to manage flooding. This is known as River Management. Often these steps involve trying to lengthen the amount of time it takes for water to reach the river channel, thereby increasing the lag time.

Hard engineering methods tend to be more expensive and have a greater impact on the river and the surrounding landscape. They will require more extensive alterations to the river to try to stop flooding.

Soft engineering methods are usually more ecologically sensitive. They will attempt to manage flood rather than prevent it.

Here we discussed two methods which are given below

Hard-engineering

Dams

Built along the course of a river to control the amount of discharge. Water is held back by the dam and released in a controlled way.

Water is usually stored in a reservoir behind the dam. This water can then be used to generate hydroelectric power or for recreation purposes.

Expensive to build.

Settlements and agricultural land may be lost when the river valley is flooded to form a reservoir.

Flood walls

Can be used to raise the height of the river bank to a level where the river might not burst its banks.

Can be permanent features or incorporated into the design of an area and become invisible.

Can also be temporary structures where flood gates or removable ‘stoplogs’ are built to protect a stretch of river.

Levees and embankments

Artificial levees can be built along river banks so that if the river floods, the water will not be able to breach the wall and cause damage. Levees can be expensive and can spoil the look of rivers.

Flood embankments are usually used in rural areas. They can take up a lot of space and are cheaper than flood walls but they can also cause the speed of the water in the river to be increased which will just move any potential flooding further downstream.

Straightening and Deepening

The river channel may be widened or deepened allowing it to carry more water. A river channel may be straightened so that water can travel faster along the course. The channel course of the river can also be altered, diverting floodwaters away from settlements.

Altering the river channel may lead to a greater risk of flooding downstream, as the water is carried there faster.

Soft-engineering

Wash Lands

These are areas of land where water can wash into during a flood. They are usually found in the lower course of a river. Sluice gates will be opened to allow excess water to flow into the area and flood marginal land.

It is not always easy to find acceptable areas for this to happen – especially in areas where there are many cities.

Land Use Zoning

When planning for a new settlement in an area, this can be used to divide up the flood plain into areas which experience different levels of flood risk. Red areas will be places that are likely to experience a high degree of flood risk. Yellow areas will be places where flooding is possible but unlikely. Green areas are places where it is very unlikely that any flooding will take place.

This is effective when making decisions about new building in an area but does not work in areas that are already built up.

Afforestation

Trees are planted near to the river. This means greater interception of rainwater and lower river discharge. This is a relatively low cost option, which enhances the environmental quality of the drainage basin.

Afforestation cannot prevent flooding but it can help reduce its likelihood.

WRITTEN BY: SM AND GM MANAGEMENTS GROUPS