Page 84 - Fundamentals of Geomorphology

GEOMORPHIC MATERIALS AND PROCESSES 67

Figure 3.7 The chief hydrological processes that influence the geomorphology of hillslopes and streams. Water flows over
and through landscapes in unconcentrated and concentrated forms.

Rill flow is deeper and speedier than inter-rill flow and is during dry periods. Subsurface flow may take place as a
characteristically turbulent. It is a sporadic concentrated slow movement through rock and soil pores, sometimes
flow that grades into streamflow. along distinct lines called percolines, or as a faster move-
ment in cracks, soil pipes (pipe flow), and underground
channels in caves.
Subsurface flow
Flow within a rock or soil body may take place under Springs
unsaturated conditions, but faster subsurface flow is
associated with localized soil saturation. Where the Springs occur where the land surface and the water table
hydraulic conductivity of soil horizons decreases with cross. Whereas saturation overland flow is the seepage
depth, and especially when hardpans or clay-rich sub- from a temporary saturation zone, springs arise where
strata are present in the soil, infiltrating water is deflected the water table is almost permanent. Once a spring starts
downslopeasthroughflow.Engineeringhydrologistsuse to flow,itcauses adip in thewater tablethat createsa pres-
the term interflow to refer to water arriving in the stream sure gradient in the aquifer. The pressure gradient then
towards the end of a storm after having followed a deep encourages water to move towards the spring. Several
subsurface route, typically through bedrock. Baseflow is types of spring are recognized, including waste cover
water entering the stream from the water table or delayed springs, contact springs, fault springs, artesian springs,
interflow that keeps rivers in humid climates flowing karst springs, vauclusian springs, and geysers (Table 3.3).