Online Geography Resources


Drainage Basin Processes

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Vall�e du Rieutort from Cr�te des Isards, Pyrenees, France
Image: Vallée du Rieutort from Crête des Isards, Pyrenees, France, a Creative Commons Attribution (2.0) image from geographyalltheway_photos's photostream
Concept of a drainage basin as an open system Understand the concept of a drainage basin by being able to delineate actual drainage basins on maps of appropriate scale. Understand that a drainage system is an open system that strives to maintain equilibrium through negative feedbacks.
Understand the terms perimeter, watershed, catchment, stream order and bifurcation ratio.
Be aware that drainage density and pattern vary within and between catchments.
Operation of a drainage system Understand the interplay of precipitation, evapotranspiration, interception, infiltration, throughflow, percolation, ground water store and flow, water table, surface flow or run-off, channel flow and water balance.
Mechanics of a drainage system Understand the impacts of moving water in a drainage basin, especially the change in velocity.
Understand the following terms: types of flow, channel shape, bed roughness (hydraulic radius), gradient, transportation, competence, capacity, erosion and deposition.
Understand the principle of Manning’s roughness coefficient, if only to dispel the view that streams flow more slowly in their lower courses than in their upper ones. Calculation of the coefficient is not required.
Controls on a drainage system Appreciate that controls should not be viewed in isolation from one another but as an interacting set contributing to the behaviour of a drainage system, most notably in times of flooding. Study the following controls: basin size, shape and relief (including slope), atmospheric controls, rock type, soil, land use and vegetation.
Understand hydrographs and how they vary in form in response to controls, and how to use them as an aid to explain discharge. on facebook
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