Do rivers burst their banks or follow their ancient course?

The Hamerkop nest by the road
April 30, 2018
Contributing to a better understanding of the life of birds
May 4, 2018

Do rivers burst their banks or follow their ancient course?

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The long-awaited rains experienced this season have resulted in unprecedented harm in many parts of the country. From floods in major towns to landslides leading to loss of lives and damage to property.

Throughout history, humans have found it favourable to build around rivers. This is because, rivers provide an easier access to a source of water for consumption, agriculture, and for industries. They also provide transportation routes and energy (hydroelectric). Sometimes we use rivers as a channel for waste disposal – unfortunately. The river valleys provide a flat area for construction and agriculture.

Motorists stranded near Kitui junction after Mwingi-Matuu road floods following heavy rains. © Twitter

However, human populations have gone further to live on river banks and inside rivers themselves. In such cases, this is a disadvantage as a river’s flow of water is never constant and can change at any time.

Floods occur when a river bursts its banks and the water spills onto the floodplain. In most cases, floods are caused by a heavy downpour. This will happen when rainwater reaches the river channel at a faster rate resulting in a flood situation.

The short-term impact of floods brings about calamities. But floods can have positive long-term effects as well. Naturally, floods are a consequence of streamflow in a continually changing environment. Therefore, floods are not entirely bad as they have been in existence throughout earth’s history and as long as we have a water cycle, we will continue to experience floods.

What encourages flooding?

  • A steep-sided channel (river valley). A river channel surrounded by steep slopes causes fast surface run-off resulting to flooding.
  • A lack of vegetation or woodland. Trees and plants intercept rainwater. If there is little to no vegetation in the drainage basin, the surface run-off will be high.
  • A drainage basin, consisting of mainly impermeable rock. This will mean that water cannot percolate through the rock layer, and so will run faster over the surface.

Floods cut off roads in Westlands, Nairobi © Twitter

Solutions to prevent flooding

Globally, a number of countries have a Disaster Management Plan that actually works. Within this plan, these countries will even go further to the specific disasters that are likely to occur in the country.  In such a flooding situation, a Flood Risk Management Plan is implemented.

Short-Term Flood Risk Management Plan

Governments need to provide funds for social assistance to the affected people, promote upstream plantation to prevent downstream flooding and enable infrastructure improvement.

Community awareness and preparedness for floods in flood-prone areas should be mandatory. The community should be able to understand why floods occur in their zone every rainy season and how they can stay safe.

Long-Term Flood Risk Management Plan

There are a number of steps we can use to prevent flooding in the long term. This includes river engineering, dam constructions, afforestation and planning controls to restrict urban development on floodplains. Technically, these steps involve trying to lengthen the amount of time it takes for water to reach the river channel, thereby increasing the lag time and preventing flooding on the floodplains. Some of these techniques may cause more environmental risks when not well monitored or evaluated such as dams and river engineering.

Dams are able to hold back water and released in a controlled way. They are built next to the river and acts as a reservoir. However, building dams without proper inlets or outlets do not qualify as dams and will not assist to control flooding. For river engineering, a river channel is widened, deepened, altered to divert flood water and straightened allowing it to carry more water. However, this may lead to a greater risk of flooding downstream, as the water is carried there faster. This two techniques sometimes requires moving people and incurs heavy costs.

Afforestation and/or reafforestation is very effective to prevent future flooding. This involves planting trees near the river which will enhance the capture of rainwater and lower river discharge. Rivers can also be allowed to flood in natural areas than where there are settlements.

Policies

The National Government could introduce policies to control urban development close to or on the floodplain. This reduces the chance of flooding and the risk of damage to property and loss of lives.  Planning regulations and controls need to be implemented even though this might face opposition to development restrictions, especially in areas where there is a shortage of housing. This may occur on flood plains, which with little knowledge, when a settlement is put up, flooding will definitely happen.

For effective flood management strategies, we should always consider the economic, environmental and social aspects for to ensure sustainability. This should not compromise future generations.

Floods in Garissa © Twitter

Knowledge is key

Floods are distressing to communities and nations at large. When developing strategies, the flood potential risks shown on a floodplain map or piece of paper should reflect that of the actual world. Therefore, their needs to be in depth knowledge and communication on the know-how of rivers.  We need to understand whether the river will flood to enable an effective evacuation plan. There is also the need to be aware of what information is available and make sure the strategies, operating and emergency action plans are up to date.

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Vicki Wangui

Vicki Wangui is a believer in all things beautiful. A believer in spreading information in regards to environmental awareness. A believer in sharing all that is good in Kenya's natural world. A believer in speaking truth with no boundaries. Do you have a story, photo, experience or message you need to share? Send your work to vicki@nyikasilika.org or vickiwangui26@gmail.com.
Share The Wild Side
Vicki Wangui
Vicki Wangui
Vicki Wangui is a believer in all things beautiful. A believer in spreading information in regards to environmental awareness. A believer in sharing all that is good in Kenya's natural world. A believer in speaking truth with no boundaries. Do you have a story, photo, experience or message you need to share? Send your work to vicki@nyikasilika.org or vickiwangui26@gmail.com.

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