This is a summary of the entire AS Level Core Physical Geogeaphy year that got me an 8 at A level. It contains statistics and case studies while leaving space for geographical drawings to facilitate revision. it contains 1. hydrology and Fluvial Geomorphology 2. Atmosphere and weathering 3. rocks a...
Geography: Physical
Hydrology and fluvial geomorphology (rivers)
Watershed – the dividing line which separates two adjacent drainage basins.
Mouth – the end point of a river where it enters the sea.
Tributary – the name given to a smaller river joining a bigger river.
Source – the place where a river begins, usually in an upland area. It may be from a spring, melted water
from a glacier or in a swampy area.
Confluence - the point where a tributary meets the main river.
System = set of processes that work together to do something
The hydrological cycle → a closed system. (water cycle)
Closed system = loads of processes but no inputs or outputs nothing comes in or leaves.
The drainage basin system → an open system.
Open system = inputs and outputs entering and leaving.
Groundwater store – water found underground in cracks in the bedrock.
Interception – precipitation that does not reach the soil but is intercepted by leaves.
Surface water – any body of water above ground inc. rivers, lakes, puddles…
,Channel storage- the vol. of water at a given time in a channel or body of water.
Soil water storage - the total amount of water that is stored in the soil (in pores).
Through fall – the process where wet leaves shed excess water onto the ground.
Stem flow – flow of intercepted water down the stem or trunk of a plant.
Surface run off (overland flow)– when water runs along the surface of the ground because the ground is
either impermeable or saturated.
Discharge (channel flow) – the movement of water within a river, channel or stream.
Infiltration - the process by which water in the surface enters the soil (vertical movement through pores).
Percolation - liquid slowly passes into the bedrock through pores (vertical movement).
Throughflow – the flowing of liquid though something (horizontal movement).
Groundwater flow (base flow) – horizontal movement through the bedrock towards a stream. Very slow
process.
Evaporation – process of turning from liquid to vapour, an output of the drainage basin.
Evapotranspiration – water that leaves the drainage basin – a combination of evaporation and
transpiration.
Transpiration – water vapour exits leaves through the stomata (pores on underside of leaf). Output of
drainage basin.
Water budgets/balances.
- A water budget re-elects the relationship between input and output of water through a region.
,A = soil moisture surplus
B = soil moisture utilization
D = soil moisture deficit
E = soil moisture recharge.
Drainage basin characteristics & factors affecting runoff & river discharge.
- Lots of vegetation interception and surface run off
- Ploughed farmland rate of infiltration surface water + surface run off.
- Antecedent moisture = lots of precipitation so soil will become more saturated (reaches field
capacity) more surface water + run off.
- Frozen ground saturates soil meaning surface water. ( infiltration + percolation)
- Rocky surface (slate) = more impermeable surfaces surface run off.
- Urban development = more impermeable surfaces surface run off + water travels faster to
river through drainage systems.
- High drainage density = lots of streams in a drainage basin leading to 1 main river lots of channel
flow.
Antecedent moisture = prolonged precipitation for days, weeks, previously.
Clay = impermeable → more surface water + run off
Vs
Sandy soil = permeable → more infiltration + ground water.
Ground water
, Hydrographs
- Show the level of discharge in a river over the course of a year.
- Allows you to see what months are most likely to flood.
What effects the shape of the hydrograph?
- Geology + soil → permeable vs impermeable = steep rising limb + short lag time.
- Gradient of drainage basin
- Land use (concrete or woodland)
- Type + amount of precipitation (snow creates flat limb + short lag time).
- Drainage density
- Porosity (capacity of rock to hold water).
- Basin shape (circular basin results in water reaching river faster than linear basin).
- Amount + type of vegetation – deciduous (leafy) vs coniferous (pines, evergreens).
Cockermouth - flooding case study
19th November 2009
Causes of the flooding
Physical:
- Confluence of 2 rivers just outside of Cockermouth – river Cocker + river Derwent. Doubles the
discharge.
- In NW of England where there is large amounts of rainfall, a particularly severe period of
antecedent rainfall in November led to soil being saturated and more surface run off.
- Skiddaw slate → rock type in area around Cockermouth (impermeable) prevents infiltration +
percolation more surface run off reducing lag time + discharge.
- 2 competing air masses of similar densities met low pressure weather stayed in place for about
24 hours.
- Azores had sea temperature 2-3 degrees warmer than average which supplied moisture for the air.
- Warm moist air from south Atlantic (Azores) was blown by prevailing SW wind. When it reached
high relief of the lake District the warm air rose, cooled and condensed into heavy orographic
(relief) rainfall.
Human:
- Lack of dredging, the river cocker had not been dredged in 2 years meaning silt and sediment had
built up in the river.
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