Flood hydrographs Flashcards
What is a flood hydrograph used for?
To represent rainfall for the drainage basin of a river and the discharge of the same river on a graph
What is Discharge?
The volume of water passing through a cross-sectional point of the river at any one point in time, measured in Cubic Metres Per Second.
What is the Rising Limb?
The line on the graph that represents the discharge increasing.
What is the Falling Limb?
The line on the graph that represents the discharge decreasing.
What is the Lag Time?
The time between peak rainfall and peak discharge.
What is the Baseflow?
The level of groundwater flow.
What is Stormflow?
Comprised of overland flow and throughflow.
What is Bankfull Discharge?
The maximum capacity of the river. If discharge exceeds this then the river will burst its banks and be in flood.
What is a Flashy Hydrograph?
Short lag-time and high peak discharge, most likely to occur during a storm event, with favourable drainage basin characteristics.
What is a Subdued Hydrograph?
Long lag time and low peak discharge
What are some of the features of Flashy Hydrographs?
- Short Lag Time
- Steep Rising and Falling Limb
- Higher Flood Risk
- High Peak Discharge
What are some of the features of a Subdued Hydrograph?
- Long lag time
- Gradually Rising and Falling Limb
- Lower flood risk
- Low peak discharge
What are some natural factors that cause Flashy hydrographs?
Vegetation Cover, Low Temperatures, High Rainfall Intensity
How does High Rainfall Intensity cause Flashy Hydrographs?
Higher discharge potential from the river and more likely for soil to reach its field capacity, thus increasing surface run off and decreasing the lag time.
How does Low Temperatures cause Flashy Hydrographs?
Less evapotranspiration so greater peak discharge.
