2B - Impact of Physical Factors
Physical factors within drainage basins determine the relative importance of inputs, flows and outputs (climate, soils, vegetation, geology, relief)
Basics of drainage basins
A drainage basin is the area of land drained by a river and its tributaries, sometimes referred to as a river catchment. The boundary of a drainage basin is defined by the watershed.
The drainage basin is a subsystem within the global hydrological cycle. It is an open system with external inputs and outputs. Since those inputs vary over time, so does the amount of water in the drainage basin. Drainage basins vary in size from that of a small local stream up to a huge river such as the Amazon. The drainage basins of tributary streams and small rivers nestle within the drainage basins of larger rivers.
Climate
Soils
Geology
Relief
Vegetation
A drainage basin is the area of land drained by a river and its tributaries, sometimes referred to as a river catchment. The boundary of a drainage basin is defined by the watershed.
The drainage basin is a subsystem within the global hydrological cycle. It is an open system with external inputs and outputs. Since those inputs vary over time, so does the amount of water in the drainage basin. Drainage basins vary in size from that of a small local stream up to a huge river such as the Amazon. The drainage basins of tributary streams and small rivers nestle within the drainage basins of larger rivers.
Climate
- Mainly impacts on the inputs and outputs
- Climate has a role in influencing the type and amount of precipitation overall and the amount of evaporation (i.e. the major inputs and outputs)
- Climate also has an impact on vegetation type
Soils
- Largely affect the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- Soils determine the amount of infiltration and throughflow, and indirectly, the type of vegetation
Geology
- Largely affects the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- Geology can impact on subsurface processes such as percolation and groundwater flow (and, therefore, on aquifers)
- Indirectly, geology affects soil formation.
Relief
- Largely affects the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- Relief can impact on the amount of precipitation.
- Slopes can affect the amount of runoff.
Vegetation
- Largely affects the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- The presence or absence of vegetation has a major impact on the amount of interception, infiltration and occurrence of overland flow, as well as on transpiration rates.