River Management: Geography WJEC: GCSE (9:1)

Flood hydrograph

Graph of stream discharge over a time period for a specific place

Peak rainfall

The greatest amount of rainfall that falls in a storm.

Peak discharge

The greatest volume of water that flows in the river at a given time.

Lag time

Time between peak rainfall and peak discharge.

Rising limb

The period of rising river discharge following a period of rainfall.

Falling limb

The decrease in river discharge as the river returns to its normal level.

Base flow

Normal discharge of the river.

Hard engineering

The use of concrete and large artificial structures by civil engineers to defend land against natural erosion processes.

Dam

A structure built across a river to control the river's flow.

Reservoir

A large natural or artificial lake used as a source of water supply that builds up behind a dam.

River straightening

Blocking off meanders, also known as channelisation.

Embankments

Raised banks constructed along the river; they effectively make the river deeper so it can hold more water.

Flood relief channels

Building new artificial channels which are used when a river is close to maximum discharge.

Soft engineering

A sustainable approach to managing the river system without using artificial structures

Flood warnings

The Environmental Agency providing reliable advance information about possible flooding.

Preparation

Using sandbags or removing valuables to a safe area away from rising flood waters.

Flood plain zoning

This attempts to organise the flood defences in such a way that land that is near the river and often floods is not built on.

Planting trees

This increases interception and increases the lag time and decreases the flood risk.

River restoration

Modifying the course of a river to return it to its natural state