Storm Hydrograph

Question 1

Discuss size of drainage basin

Answer 1

Lag Time is shorter, peak discharge is higher in smaller basin. water reaches channel more rapidly.

Question 2

Shape of drainage basin

Answer 2

Lag time is shorter, peak discharge is higher in a more circular basin. It takes less time for more water to reach the channel due to each tributary being equidistant from channel.

Question 3

Relief of drainage basin

Answer 3

Lag time is shorter and peak discharge is higher in steeper basin. Water reaches channel more rapidly in steeper basin because water travels quicker downhill.

Question 4

Length of rainfall

Answer 4

Lag time is shorter and peak is higher after prolonged rainfall. The ground is saturated with water, so there is more surface runoff.

Question 5

intensity of rainfall

Answer 5

Lag time is shorter and peak is higher after intense rainfall. Where rainfall is falling faster the infiltration rate, there is excess surface runoff.

Question 6

Type of precipitation

Answer 6

Lag time is slower and peak is lower after snowfall. Snow does not reach the channel but is stored on the surface. It melts eventually the melt water reaches the channel quickly as the ground is frozen, therefore no infiltration.

Question 7

Permeability of rock type `

Answer 7

Lag time is shorter and peak is higher in an area of impermeable rock type. Impermeable rocks are saturated more quickly than porous and pervious rocks. Overland flow is more common.

Question 8

Vegetation

Answer 8

Lag time is slower and peak is lower in forested basin. vegetation intercepts a large proportion of rainfall. where trees are deciduous, discharge is higher in a forested basin in winter as there is less interception.

Question 9

Soil texture and structure.

Answer 9

lag time is slower and peak is lower in areas of sandy soil. Sandy soils have larger pore spaces, and clay spoils have small pore spaces. Infiltration is more rapid in sandy soils.

Question 10

Urbanisation

Answer 10

Lag time is faster and peak is higher in an urbanised catchment. Surface runoff is higher in urban areas because the urban surfaces are impermeable and water travels as surface runoff.

Question 11

deforestation

Answer 11

Lag time is faster and peak is higher in a deforested catchment. There is less interception and ET and more surface runoff in a deforested catchment.