topographic metrics
DESCRIPTION
Topographic Metrics. Many Topographic metrics have been proposed. We’ll 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 PresentationTRANSCRIPT
Topographic Metrics• Many Topographic metrics have been
proposed. We’ll 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?
80-90% Relief is on Bedrock Channels
Blue lines: drainage area > 1km2
80-90% Relief is on Bedrock Channels
Threshold hillslope gradients dominate – no tectonic info
Now in 3D
The 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-
Fluvial Scaling – Empirical Data
• Linear relationship between log(S) and log(A)
• ks is the channel steepness; is the concavity
Flint’s Law: Mixed Bedrock-Alluvial Stream (Appalachians, VA)
Flint’s Law: Mixed Bedrock-Alluvial Stream (Appalachians, VA)
S = ksA-
ks is a more-general equivalent to the SL index:No dependence on basin shape
colluvialreach ks-
Duvall, Kirby, and Burbank, 2004, JGR-ES
ks
S = ksA-
Concavity invariant with U
Steepness varies with U
Debris-flow chutesexpand with U
Question: What Sets Erosion Rate?
E = KAmSnTransient systems• Knickpoint in long profile• Break in slope-area scaling