Hydrographs Flashcards

All 6 cards in this deck

What is a storm (flood) hydrograph?

A graph showing rainfall and river discharge at a point on a river over the period of time following a storm.

What is river discharge, and in what units is it measured?

The volume of water passing a point in the river per second, measured in cumecs (cubic metres per second).

What is lag time on a hydrograph?

The time between peak rainfall and peak discharge.

True or false? A long lag time on a hydrograph means a higher risk of flooding.

False. A short lag time with a steep rising limb and high peak discharge (a flashy hydrograph) means a higher flood risk.

What is peak discharge on a hydrograph?

The highest discharge the river reaches after the storm, shown by the top of the discharge line.

What do the rising limb and the falling limb of a hydrograph show?

Rising limb: discharge increasing as rainwater reaches the channel. Falling limb: discharge decreasing back towards normal after the peak.