Hydrographs Flashcards
What is a river regime?
a graph showing how a river’s discharge responds to changes in precipitation throughout the year
What is lag time?
the time between peak rainfall and peak discharge on a hydrograph
What factors affect lag time?
- shape and size of drainage basin
- permeability of surfaces
- temperature
- duration of rainfall
- vegetation cover and type
What is the rising limb?
shows how quickly discharge rises after a rainstorm
What is the falling limb?
shows the reduced discharge once the main effect of runoff has passed
what is the peak flow?
the highest recorded discharge
What is bankfull discharge?
marks the level of discharge above which flooding will occur
Why is discharge measured?
- predict flood events
- support irrigation
- flood management
- resource management
- track the impacts of climate change
How does drainage basin size affect lag time?
larger basins -> water take longer to travel to river -> increases lag time
How does the amount of vegetation impact lag time?
more vegetation -> more interception -> takes longer for water to reach the river
How might speed of snow melt impact a river’s discharge?
faster snowmelt leads to sharp increases in discharge
(happens in nordic countries in summer)
What is a flood hydrograph?
indicates how discharge of a river responds to storm events
What is the shape of a flashy hydrograph?
steep rising limb and high peak discharge
What is the shape of a flat hydrograph?
shallow rising limb, lower peak discharge
Why are hydrographs used?
- see response of discharge to storm event
- flood management
- predict flooding
- comparison of catchments/rivers
