Drainage Basin Features Flashcards
Confluence
The ‘junction’ at which the tributary joins the main river
Rill Action
Strength of the water
Sheet Flow
Shallow flow due to rainfall overland
What makes a high density drainage basin?
Impermeable land surface Steep slopes Limited vegetation cover Limited rainfall Large channel frequency (Tributaries)
What makes a low density drainage basin?
Permeable rock e.g. Chalk Much vegetation cover Limited rainfall Gentle slopes Lower Channel frequency
Tributary
Side river which joins the main river
Impermeable surfaces
Found in urban areas with Tarmac - leads to rapid surface run off via drains and sewers resulting in quick transfer of water to the river
Shorter lag time
Found in urban areas with impermeable surfaces and is the short amount of time between peak rainfall and peak discharge
In urban areas
Water is moved quickly into the river and sewers leading to a steep rising limb
In rural areas
Infiltration is greater, this results in transfer via groundwater flow
Slows the rainfall journey into the river
Interception by vegetation acts as a store for rainfall, delaying the transfer of water to the river
Longer lag time
Shallow falling limb
Percolation and groundwater storage delays water return to river at base flow
Inputs
Precipitation from rain clouds fed by evaporation from water sources including seas/oceans
Water Level
Related to form of precipitation
Regularity of precipitation
Duration and intensity of precipitation event
Storage
Surface - water is stored within lakes and rivers
Vegetation - Intercepts precipitation
Below surface - Groundwater - Soil permeability and rock will determine how much water can be stored as groundwater
Transportation
Water is transferred on the surface of the basin
Either; As surface run-off where water flows across the surface or via river channels within the drainage basin
Through flow and ground flow - Below the ground through the basin as it makes its way towards the river channel.
Outputs
Water can be lost directly through evaporation
Water can be lost via trees and vegetation through transpiration - evaporation from leaves
Combined output known as evapotranspiration
Loss of water through loss of water from the basin through streamflow into the sea/ocean as the river ends its journey
