2.1.3: Temporal variations in river discharge Flashcards
Drainage density
A measure of the length of the river channels and its tributaries per unit area.
Infiltration capacity of clay soil type
low infiltration capacity
Infiltration capacity of well-established pasture
high infiltration capacity and rate
Replacing lawns with paved areas and parking spaces causes
peak in hydrograph in urban drainage systems
Factors that affect how a river responds to a rainfall event
3
size of the drainage basin
shape of the drainage basin
drainage density
High drainage density effect on hydrograph
Peak in hydrograph, flashier flows
River discharge
The amount of water flowing down a river at any given time. (measured over the course of a day or a year)
River regime
The flow of a river over the course of a year
Storm flow
Storm runoff resulting from storm precipitation can contribute to high but short-term peaks in river discharge.
Base flow
Groundwater supplies the river between periods of precipitation and feeds steadily into the river, causes the normal minimum flow of a river.
Simple regime
Periods of high and low channel flow which may correspond with seasonal temperature and rainfall changes
Complex regime
Lots of peaks and troughs throughout the year with many tributaries that flow through different environments and climates.
Peak discharge
The maximum rate of flow during a storm event
Peak rainfall
The maximum rainfall recorded in one of the time intervals
Rising limb
The part of a storm hydrograph in which discharge starts to rise.
Lag time
The time elapsed between peak rainfall and peak discharge
Falling limb
The part of the storm hydrograph in which the discharge starts to fall.
Preceding discharge
The rate of flow prior to the latest storm event
Bankfull discharge
The maximum discharge reached during a storm event prior to overtopping of the river banks an the inundation of the floodplain with excess water.
Axis on a hydrograph
x: time
y: normally 2 labels: river discharge and rainfall
River discharge units
cumecs
Two types of hydrograph extremes
flashy and flat
Flat hydrograph characteristics
4
low peak discharge
gentle rising limb
gentle falling limb
long lag time
Flashy hydrograph characteristics
3
high peak discharge
steep rising limb
short lag time
