1.1.2 Flood Hydrographs

Question 1

Flood hydrographs…

Answer 1

represent rainfall for drainage basin of a river and the discharge of the river

Question 2

Discharge

Answer 2

volume of water passing through a cross-sectional point of a river over time. Measured in cubic metres per second (cumecs). Made of baseflow + stormflow

Question 3

Features of flood hydrograph

Answer 3

Rising limb, falling limb, bankfull discharge, lag time, stormflow, baseflow

Question 4

Axes of flood hydrograph

Answer 4

x - time, y - discharge (cumecs) & rainfall (mm/hr)

Question 5

Rising limb

Answer 5

Line showing discharge increasing

Question 6

Falling limb

Answer 6

Line showing discharge decreasing

Question 7

Lag time

Answer 7

Time between peak rainfall and peak discharge

Question 8

Baseflow

Answer 8

Level of groundwater flow

Question 9

Stormflow

Answer 9

Overland flow + throughflow

Question 10

Bankfull discharge

Answer 10

Max capacity of river. After this the river banks will burst causing flooding

Question 11

Features of a flashy hydrograph

Answer 11

short lag time
high peak discharge
Steep limbs
Higher flood risk

Question 12

Features of a subdued hydrograph

Answer 12

Longer lag time
Low peak discharge
Gradual limbs
Lower flood risk

Question 13

Natural causes of flashy hydrographs

Answer 13

High rainfall intestity, antecedent rain (rain prior to event being measured), impermeable rock, high drainage (many tributaries), small, circular, or steep basin, precipitation type (snow increases lag time)

Question 14

Human causes of flashy hydrographs

Answer 14

Urbanisation, pastoral farming, deforestation