Activity One - Structural Measures

We will be looking at four different ways that are used to mitigate floods; dams, afforestation, channel modification and levees. We are looking at these three categories as you are required to look at a river in its entirety and not just a specific section.

Dams

Dams are often found in the upper course of the river where the store of water is easier due to the shape of the landscape. Dams are expensive to build and therefore are often used for a variety of purposes. Those dams that have a number of uses are called 'multi purpose dams'. But how successful are dams in controlling the flow of water in a drainage basin? To answer that question we are going to be exploring the impact that the Three Gorges Dam has had on China.

• • 1. Using the link below in the 'Useful Resource' box create a detailed example of the cost and benefits of using a dam to control flooding. You could use the worksheet to help you structure your notes.

Useful Resource

China's Three Gorges Dam - An Update

Afforestation

Afforestation is used as a more natural way to prevent flooding. The idea is that the precipitation will be intercepted by the trees and therefore slow down the water reaching the river. It is seen as a less intrusive way to control the flow of water in a drainage basin but how successful is it?

• • 1. Read the article in the 'Useful Resources' box below and make notes on how afforestation is being used in the UK.

Useful Resource

The Guardian - Planing more trees can reduce UK flooding research shows

Channel Modification and Levees

Channel modification is when the river channel is altered to either make the carrying capacity of the river greater or to move the water away from the area more efficiently. Channels can be dredged, straightened or even diverted but does it work?

• • 1. Write a summary of what dredging, channelisation and bank protection is.

    2. Complete a cost-benefit analysis of channel modification.

    3. Complete a detailed example of the Mississippi River and discuss how successful the hard management has impacted the river and the surrounding area.

Useful Resources

Our Planet's Freshwate Textbook by Codrington.

The Atlantic - What we've done to the Mississippi River: An Explainer

Scientific America - Levees and the illusion of Flood Control

Flood Plain Management

Lots of houses are built on flood plains as the land is flat and easy to construct on. Transport networks also criss cross the area in the lower course of the river. As flood plain areas have increasingly been seen as areas of value, rivers in these areas are being managed. For this example we are going to focus on the Kissimmee River Drainage Basin.

• • 1. Read the article and watch the youtube clip in the 'Useful Resources' box to create a detailed example of what has happened to the Kissimmee River.

Activity Two - Planning Measures

As well as hard management of a river to control the flow of water there are a series of different planning processes that can occur to reduce the impact of flooding. How successful though can planning actually be when the severity of flood events is not always predictable? Read the three articles in the 'Useful Resources' box and describe how personal insurance, flood preparation and flood warning technology can mitigate floods.

Useful Resources

Houston Chronicle - Build, flood, rebuild: flood insurance's expensive cycle

New York Times - Tokyo is Preparing for Floods ' Beyond Anything We've Seen'

Floods

Reuters - From Bhutan to Cambodia, early warning saves lives in floods

Activity Three - Debate

For this activity the class is going to be divided into two. One team will argue whether structural measures of control are more effective than planning measures and the second team will do the opposite. The resultant discussion from this debate will help you to answer the essay question in the 'exam style question' section.