option A flood mitigation

Question 1

hydrograph elements

Answer 1

rising limb
peak flow/ discharge
lag time
run off curve
base flow
recessional limb

Question 2

rising limb

Answer 2

-amount of discharge and speed at which its increasing
-(flash flood= very steep)
-generally steep in urbanised catchments

Question 3

peak discharge

Answer 3

-higher in larger basins
-steep catchments- lower infiltration rates
- flat catchment- high infiltration rates so more through flow and lower peaks.

Question 4

lag time

Answer 4

-time interval between peak rainfall and peak discharge
-influenced by basin shape, steep, stream order

Question 5

runoff curve

Answer 5

-relationship between overland flow and throughflow
-low infiltration=high moisture, impremeable surface, strong rainfall, overland flow

Question 6

base flow

Answer 6

-seepage of groundwater into the channel
-slow movement and main long term supply of river discharge

Question 7

how does seasonal change impact (river regime)

Answer 7

• amount and nature of precipitation
  -seasonal variations in temperature and evapotranspiration
  -changes in vegetation cover
  variations in rock, soil types and shape and size of basin

Question 8

recurrence interval

Answer 8

frequency in which events of a certain size occur

Question 9

catastrophe of flood

Answer 9

high magnitude but low frequency

Question 10

urbanisation hydrological impact

Answer 10

-shorter lag time
-steeper rising limb
- higher peak flow
-steeper recessional limb

Question 11

factors influencing flood risks

Answer 11

-precipitation type and intensity
- temperature+
evapotranspiration
-antecendent moisture
-size of basin
drainage density
rock and soil impermeability
-slopes
-vegetation type
-land use

Question 12

how did urbinization increase flood risk

Answer 12

-creation of impermeable surfaces (roads, roofs, pavements)
-smooth surface served with dense network of drains gutters and underground swerves- increase in drainage density
-natural river channels often constricted by bridge supports or riverside facilities- reduce carrying capacity

Question 13

impact of urbanisation on lower part of basin

Answer 13

• increased erosion.
• more water getting into rivers
  increased speed of flow and transport of materials- enlarged channels
  .less erosion due to riverbank protection schemes

Question 14

deforestation

Answer 14

removal of tress and forest and their ecosystems

Question 15

deforestation effects of hydrological cycle

Answer 15

-more overland flow leading to more frequent erosion
-rivers transporting more sediment
-reduced evapotranspiration

Question 16

channel modifications examples and explanations

Answer 16

-channelisation (create new channels)
-enlargement (synthetic levees on preexisting channels so that more water is moved)
-straightening

Question 17

flood mitigation
examples

Answer 17

-ways of reducing flood risk
dams
afforestation
channel modification
planning

Question 18

dams
purpose and implications on environment and society

Answer 18

-hold back water during times of flood and release when risk is gone
-benefits to agriculture, energy production (hydroelectric), navigation, recreation, tourism
-increased water loss due to evaporation
-channel erosion downstream
decline in sediments reaching deltas, or ocean.

Question 19

reservoirs

Answer 19

store excess rainwater in upper drainage basin

Question 20

afforestation

Answer 20

-flood abatement=decreasing amount of runoff which reduces flood peak
-increase amount of interception and reduce overland flow

Question 21

planning

Answer 21

planning for floods:
-personal insurance
-being prepared for flooding (sandbags, sealing doors and windows, moving electrical generators)

Question 22

insurance problem

Answer 22

-people in LIC’s may struggle to get insurance incase of flooding

Question 23

flood prediction

Answer 23

predicting flood occurrences and strength to prepare for extreme weather events

Question 24

things to improve flood warnings

Answer 24

-improved rainfall and snow pack estimates
-better river gauging (data collection)
-more current information about human populations and infrastructure
-technology shared among all agencies involved in forecasting and risk assessment