Summary Core Physical Geography (Topic 1-3)

Paper 1: Core Geography

Physical core

Topic 1: Hydrology and Fluvial Geomorphology
1.1 The Drainage Basin System

Hydrological Cycle -> cycle of water between air, land, sea

Drainage Basin -> Area of land that drains water by river and it’s tributaries, land where any precipitation
will drain into

Drainage basin = Open System allows movement of energy and matter across boundaries:

• 1 main input: Precipitation

• 2 outputs: Evapotranspiration and overland flow

• 3rd output: Leakage -> Occur from deeper subsurface to other basins

Water Storage in cycle:
• Interception storage (vegetation)
• Surface Storage
• Soil moisture storage
• Groundwater storage
• Channel storage

Human Modifications (example)
 Large scale changes of channel flow and storage
 Irrigation (supply water) and land drainage
 Large scale abstraction of groundwater and surface water for domestic/industrial use
 Urbanization -> converting land into concrete surface

Watershed – Catchment area of drainage basin

Drainage Density
 Total length of all streams in drainage basin divided by total area of drainage basin
 Measures how well/poorly water is drained by stream channels
 More streams, better drained (steeper rising limb and peak flow)

Stream Ordering
 Numbering streams part of drainage basin network
 1st order streams – numerous
 Higher order streams - fewer

Bifurcation Ratio
 Ratio of num of stream segments of one order to number of
next higher order
 BR low, less than 2.5 means it’s complex (branched)
 BR high, large num of 1st order streams joining main channel (higher risk of flood)
 Example:
Stream order 1 = 27