factors affecting floods

Question 1

bifurcation ratio

Answer 1

how many L1 streams can create an L2 streams when they merge together
- lower ratio = water is only concentrated in one channel

Question 2

rock types [geological factors]

Answer 2

permeability of rocks:
- more permeable rock = higher likelihood of infiltration taking place
- also represents amount of base/throughflow
- lower hydrograph peaks & higher lag time

Question 3

land use

Answer 3

e.g. how vegetation cover increases lag time
- contributes to interception storage & higher infiltration rates]
- influences lag time & peak discharge

Question 4

drainage density

Answer 4

how frequently streams occur on land
- average length of a stream within a unit area, influenced by climate & geology
- higher density = higher flood peaks [water flows faster in the channels]

Question 5

relief

Answer 5

difference between the heights of high and low points on a map
- steeper slope = higher peaks & steeper rising limb in a hydrograph

Question 6

basin circularity

Answer 6

more circular basin = higher peaks & lower lag time
- the distance that water has to cover to enter & exit the basin is the same all around due to similar radius

Question 7

basin elongation [part of circularity]

Answer 7

largest dimension of basin with the circle’s diameter
- more elongated basin = lower peaks and higher lag time [water arrives in a staggered fashion]

Question 8

precipitation type

Answer 8

heavier ppt = rapid overland flow generation
- infiltration rate is overwhelmed with too much ppt
- results in a flashy hydrograph