topographic metrics

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Topographic Metrics. Many Topographic metrics have been proposed. Well examine the three most common Channel Steepness Index Hillslope Gradients Local Relief at Various Scales What are the relationships among these? Which are most useful for gaging the influence of tectonics on topography?. - PowerPoint PPT Presentation

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  • Topographic MetricsMany Topographic metrics have been proposed. Well examine the three most commonChannel Steepness IndexHillslope GradientsLocal Relief at Various ScalesWhat are the relationships among these?Which are most useful for gaging the influence of tectonics on topography?

  • 80-90% Relief is on Bedrock ChannelsBlue lines: drainage area > 1km2

  • 80-90% Relief is on Bedrock ChannelsThreshold hillslope gradients dominate no tectonic info

  • Now in 3DThe Same Drainage Basin in Taiwan

  • Beware: Many authors use hillslope relief and local relief (measured over up to 5km radius) as interchangeable

  • Empirical data for well-adjusted fluvial systems around the globe yield the following scaling:

    S = ksA-q

    Fluvial Scaling Empirical DataLinear relationship between log(S) and log(A)ks is the channel steepness; q is the concavity

  • Flints Law: Mixed Bedrock-Alluvial Stream (Appalachians, VA)

  • Flints Law: Mixed Bedrock-Alluvial Stream (Appalachians, VA)S = ksA-qks is a more-general equivalent to the SL index:No dependence on basin shapecolluvialreachks-q

  • Duvall, Kirby, and Burbank, 2004, JGR-ESqksS = ksA-q

  • Concavity invariant with USteepness varies with UDebris-flow chutesexpand with U

  • Question: What Sets Erosion Rate?

  • E = KAmSnTransient systemsKnickpoint in long profileBreak in slope-area scaling

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