Runoff Variation And The Flood Hydrograph

Question 1

How can river flow be measured?

Answer 1

River regimes and hydrographs.

Question 2

How does an area influence a hydrograph?

Answer 2

For Example:
Large basins produce higher peak discharges,
Small basins experience a shorter lag time (can be known as ‘flashy’) - because the water has less distance to travel.

Question 3

How does shape influence a hydrograph?

Answer 3

For Example:
Circular basin will be flashy because all boundaries are an equal distance away from the river at any one point.
peanut shaped basins will produce a double peak discharge as the water flows from the lower section, and then the upper section.

Question 4

How does relief influence a hydrograph?

Answer 4

For Example:
Steep relief causes a higher surface runoff, however infiltration rates are lower on steep slopes, and this is opposite for shallow slopes.

Question 5

How does geology influence a hydrograph?

Answer 5

For Example:
Permeable rock allows percolation which stops soil becoming saturated, causing a longer lag time, so the hydrograph would appear flat.

Question 6

How does soil influence a hydrograph?

Answer 6

For Example:

Saturated soil causes rapid surface runoff which results in a flashy hydrograph.

Question 7

How does land use influence a hydrograph?

Answer 7

For Example:
Urban land use - there is more concrete (impermeable) so more surface runoff, and less infiltration - so a shorter lag time and a flashy hydrograph result.

Question 8

How does drainage density influence a hydrograph?

Answer 8

High drainage density - more channels - so there is a faster transfer of water so the hydrograph is flashy.

Question 9

How does precipitation and temperature influence a hydrograph?

Answer 9

Extreme temperatures cause the ground to either be baked or frozen, which means less infiltration can occur, and so resultantly is flashy.
High or intense rainfall, it means quick infiltration and also fast saturation, so again is flashy.