Lecture 8 & 9 - River Channel Management

Question 1

What are direct human impacts on river channels?

Answer 1

Navigational purposes
- dredging to accommodate vessels
- locks and sluices

Question 2

How to control channel flow

Answer 2

Reservoirs

Increase channel capacity

Increase transmission rate ( removal of bars and vegetation, channel shortening)

Question 3

What are the types of resectioning of river channels?

Answer 3

• Triangular - common with ditches
• Trapezoidal - stable slope offer revegetation potential
• Rectangular - urban areas - levees

Question 4

When are levees used?

Answer 4

Used in urban areas to contain flood water.

It raises the river bank, creating a flood defence

Question 5

When are culverts used?

Answer 5

Flood control
common in urban areas, on major roads or in urbanisations

Question 6

Types of bank protection

Answer 6

1. Groynes
2. Blockstones
3. Stone walls
4. Gabions - (smaller rocks in a metal basket)
5. Rip rap - (stones protecting a river bank by absorbing water energy)
6. Vegetation - (willows)

Question 7

What are some physical effects of changing channels?

Answer 7

1. Incision due to bed scouring
2. damming - reducing sediment transportation
3. A channel is unlikely to stay straight due to the channel properties

Question 8

The hydrological affects of straight channels on a graph

Answer 8

Lag and duration time reduced
The peak discharge is greater as a result of straight channels

Question 9

What are flood maps

Answer 9

Flood maps show the area surrounding flood-prone areas. Maps usually are colour-coded in accordance with the likelihood of a flood.