Storm Hydrograph Flashcards
What is a storm hydrograph?
A graph which shows rainfall during a storm and the river discharge which follows it.
Peak rainfall
Period of most intense rainfall during a storm.
Rising limb
Increasing curve on a hydrograph leading to peak discharge.
Lag time
in small drainage basins it takes time for water to make its way to the channel, and this delay between peak rainfall and peak discharge is called lag time.
Peak discharge
Period of highest river water flow during storm or flood episode.
Falling / recessional limb
Declining slope following peak discharge on a hydrograph.
Storm runoff / stormflow
Describes all the river discharge resulting from a period of rain. It is graphically represented as the area under the curve in a hydrograph.
Base flow
Part of a rivers discharge that is contributed by the groundwater store.
Characteristics of a flat hydrograph
- gentle limbs
- low peak discharge
- long storm flow
- long lag time
- significant base flow
- flooding unlikely
Environment of a flat hydrograph
- permeable soil and rocks
- forestry
Characteristics of a flashy hydrograph
- steep limbs
- high peak discharge
- short storm flow
- short lag time
- small base flow
- flooding likely
Environment of a flashy hydrograph
- impermeable soil and rocks
- urbanisation of surfaces and drainage system
