Hard and Soft engineering

Question 1

Hard engineering involves…

Answer 1

man-made structures that aim to abate natural processes.

Question 2

Soft engineering involves…

Answer 2

alleviation, so management of the drainage basin, working with natural processes.

Question 3

Examples of Hard engineering:

Answer 3

-dams, leavees, wing dykes and straightened channels, diversion spillways (flood relief channels).

Question 4

Hard engineering may cause unexpected…

Answer 4

effects elsewhere in the drainage e.g. increased deposition, loss of habitats.

Question 5

Levees can be used to…

Answer 5

divert and restrict water flow to value land.

Question 6

Reservoirs store excess…

Answer 6

rainwater in the upper drainage basin, however, only appropriate in small drainage basins.

Question 7

Flood-proofing includes any…

Answer 7

adjustments to buildings and their contents that help reduce losses.

Question 8

Short term flood-proofing:

Answer 8

• blocking up entrance
• sealing doors and windows
• use of sandbags

Question 9

Long term flood-proofing:

Answer 9

-moving the living spaces above the level of the floodplain e.g. building on stilts.

Question 10

Land-use zoning and land-use…

Answer 10

planning has been introduced since World War Two.

Question 11

In the USA, land-use management has been…

Answer 11

effective in protecting new housing developments from 1 in 100-year floods.

Question 12

Event modification includes…

Answer 12

environmental control and hazard-resitant desing.

Question 13

Flood abatement involves…

Answer 13

decreasing the amount of runoff, reducing the flood peak in the drainage basin.

Question 14

Flood abatement:

Answer 14

• afforestation
• reseeding sparsely vegetated areas
• treatment of slopes such as ploughing
• protection from overgrazing, and clear-cutting forests
• clearance of sediment(dredging)
• preservation of natural water-stores

Question 15

Flood diversion refers to…

Answer 15

the practice of allowing certain areas such as wetlands and floodplains to be flooded to a greater extent.

Question 16

Reclamation is the process of…

Answer 16

buying land and turning it into the natural habitat and make it a national park.

Question 17

Reducing loss can be by:

Answer 17

• aid
• increased education and awareness
• bottom-up developments (micro-credit)

Question 18

Working on prediction involves:

Answer 18

• Plotting gauging stations

- analysing the drainage basin(hydrographs, recurrence intervals)

Question 19

4 ways of managing floods:

Answer 19

• hard
• soft
• manage the loss
• do nothing and accept the costs

Question 20

Straightening of the channel:

Answer 20

• maintains discharge
• limits helicoidal flow (flow at different speeds)
• keeps thalweg at the centre
• stops lateral shifting

Question 21

Artificial Levees:

Answer 21

• stops lateral erosion
• protected floodplain
• increase in CSA, channel capacity and hydraulic radius

Question 22

Wing dykes:

Answer 22

• build at 90 degrees to the banks
• slower the velocity-deposition
• keeps the river straight-increase in laminar flow
• increased vertical erosion
• thalweg at the centre

Question 23

Channelisation:

Answer 23

• the channel is covered in concrete
• reduces friction, so higher velocity and discharge
• limits thalweg shifting
• no vertical or lateral erosion
• less turbulence and eddies

Question 24

Dam:

Answer 24

-controls the discharge all year around