Hydrographs

Question 1

What does the rising limb, recessional limb and the peak show on a hydrograph?

Answer 1

-rising limb: how quickly the flood waters begin to rise
-recessional limb: speed at which the the water level in the river declines after peak
-peak flow: maximum discharge of the river as a result of the storm

Question 2

What factors effect a storm hydrograph?

Answer 2

-size of drainage basin: shorter lag time and higher peak in a smaller drainage basin as water reaches the channel more rapidly
-shape of drainage basin: shorter lag time and higher peak in a more circular as it takes less time for water to reach the channel as all extremities are equal
-relief: shorter lag time and higher peak in a steeper basin since water reaches the channel more rapidly
-length of precipitation event: shorter lag time and higher peak after prolonged precipitation since soil is saturated
-intensity of precipitation: shorter lag time and higher peak after intense rainfall
-type of precipitation: slower lag time and lower peak after snowfall as snow needs to melt
-permeability of rock: shorter lag time and higher peak with impermeable rock as rocks are saturated more quickly
-vegetation: slower lag time and lower peak in forested areas as vegetation intercepts rainfall