Geoscience Reference
In-Depth Information
Precipitation
Evapotranspiration
I nterception
Stem fl o w
Throughfall
Dynamic contibuting
area
Infiltration - excess
overland flow
Scar
Percolation
H ig
Scree
Scar
Dyke
Saturation
overland flow
Low wate r tabl
Return flow
River Wharfe
channel
River
channel
Precipitation
Interception
storage
Surface
storage
Soil moisture
storage
Groundwater
storage
St
Inf
Per
Evaporation
and Transpiration
St = Stemflow
Inf = infiltration
Per = Percolation
Figure 1.5 The cascading system of slope hydrology.
The term factor is used for any control which leads to
an effect. A process is any transformation (physical,
chemical or biological) which the environment is experi-
encing or has experienced in the past. For example, the
Carboniferous Limestone in Upper Wharfedale is broken
down by a series of weathering processes such as freeze-
thaw, root quarrying, leaching, chelation , and carbonation .
The speed at which these operate is governed by key
factors such as temperature, freeze-thaw cycles, rainfall
amount, precipitation acidity, vegetation type and amount,
and not least by the rate of removal of weathered material
by slope and soil processes to expose fresh limestone rock.
Processes in physical geography, like rock weathering,
usually involve the movements of energy and/or matter
through a series of interconnected subsystems. The output
of one subsystem provides all or part of the input of
another subsystem. For example, the movement of water
from its input in precipitation through to the channel of
the river Wharfe and its tributaries forms a cascading
system ( Figure 1.5 ). Water circulates through a number
of stores (atmospheric store, vegetation store, surface
store, soil moisture store, groundwater store) before being
removed by outputs of evaporation, transpiration and
drainage discharge.
Although both morphological and cascading systems
are convenient conceptual models, they are clearly
approximations to the many complex interrelationships
which occur between inputs, outputs, flows and morpho-
logical structures. The system which connects the
throughput of energy and matter, on the one hand, and
the morphology of the system is best explained in the third
type of system, the process-response system which links
process and form. For example Figure 1.6 illustrates the
process-form relationships between the slope subsystem
of the valley sides of Upper Wharfedale and the channel
subsystem of the river Wharfe. The relationships between
SLOPE
SUBSYSTEM
STREAM CHANNEL
SUBSYSTEM
Stream
Bedload Amount
Slope
Erosion
²
Valley-side
Slope Angle
Channel
Erosion
Figure 1.6 Connections between a morphological system
and a cascading system to give a process-response system.
 
 
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