Lesson 5 Flashcards
What is a storm hydrograph?
shows variations in a river’s discharge at a specific point over a short period of time (usually before, during and after a storm).
Why does the shape of the graph change?
changes as a result of physical and human factors, and can be described as either ‘flashy’ or ‘subdued.’
What is a Normal (base) flow?
The contribution to river flow from long-term storage sources such as permeable rocks, areas of bog and marsh and peat-covered moorland
What is Rising limb?
The increase is discharge in response to surface runoff and through-flow from a rainfall event, until peak flow is reached. In a storm the river is not important as the precipitation takes time to reach the channel.
What is Peak Discharge?
The maximum discharge by a stream or river in response to a rainfall event.
What is Bankfull discharge?
when a river’s water level reaches the top of its channel. Any further increase will result in flooding of the surrounding land.
What is Falling Limb
The decline in discharge that occurs after peak flow. This segment is usually less steep than the rising limb because throughflow is being released relatively slow into the channel.
What is Lag time?
The difference in hours and minutes between the time of maximum precipitation and the time of peak discharge. The lag time varies according to drainage basin conditions. Rivers with a short lag time tend to experience a higher peak discharge and they are more prone to flooding than rivers with a long lag time.
What is Storm Runoff?
This is the part of the river flow derived from the immediate rainfall event. The most rapid transfer of water occurs overland and via throughflow.
What is Approach Segment?
This shows the discharge of the river before the storm (the antecedent flow rate).
