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Fluvial Landforms and Processe1

Fluvial Landforms and Processe1 - cross-sectional(hydraulic...

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Fluvial Landforms and Processes Graded river over geologic time, slope and channel characteristics adjust to provide, with the available discharge, just the velocity required to transport the sediment supplied from the basin analogous to a railway grade no excess, erosion or deposition, i.e. only to maintain the channel morphology a change in any of the controlling factors will cause a displacement of the system in a direction that will tend to absorb the effect of the change (dynamic equilibrium) independent factors o discharge, sediment from the basin and base level (potential energy) o determined by climate and geology, i.e. external to the fluvial system o a change in any one of these controlling factors results in an adjustment of the stream channel by degradation or aggradation towards a new longitudinal profile, also manifest in plan view by a change in meander pattern and locally in terms of
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Unformatted text preview: cross-sectional (hydraulic) geometry • semi-dependent factors o channel width, depth, roughness, velocity, pattern and load grain size o depend on the controlling factors but also some self-regulation (dependence on each other) • dependent factors o slope of the water surface o the final adjustment, responds to the semi-dependent variable, cannot change abruptly like the other factors • rate of adjustment o depends on resistance of the bed materials and amount of energy, i.e. mass (Q) and relief (base level) o thus fastest adjustments with large Q and adjustable materials o grade can exist locally in alluvial channels bounded by barriers such as resistant rock (waterfalls) or a landslide (e.g. Battle Creek valley) o grade extends to the entire profile as the barriers are eliminated...
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