### Uncovering signatures of geomorphic process through high resolution topography

#### Stuart W. D. Grieve, University of Edinburgh

#### Landslide recurrance intervals

#### Need to understand the geometry of hillslopes

Low hanging fruit!

## How can we measure hillslope length?

A ruler?

Slope-area plots?

Drainage density?

Flow routing?

#### A ruler?

Time consuming

Subjective

Doesn't consider topography

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

#### Slope-area plots?

Picking an inflection point?

Binning or smoothing the data

Converting an area to a length

Lots of variability in results

#### Drainage density?

$$D_D = \frac{L_T}{A} $$

$$L_H \approx (2D_D)^{-1} $$

#### Drainage density?

#### Drainage density?

Little spatial variation

Sensitive to channel network

Doesn't account for channel width

Underestimates hillslope length

#### Flow routing?

#### Flow routing?

#### Flow routing?

Can be applied at a fine spatial scale

Accounts for local topography

Not subjective

#### The best method is flow routing, so what?

#### Flow routing gives us other data

## This data means we can test sediment flux laws

#### Constraining linear flux

#### Constraining nonlinear flux

#### Topographic predictions of linear sediment flux

#### Topographic predictions of nonlinear sediment flux

#### Predictions of the relief structure of landscapes

#### Topography is consistent with nonlinear sediment flux

## How else can this data be used?

#### Can we do this with more than 2 data points?

$$ E^* = \frac{-2 \color{red}{C_{HT}L_H}}{S_C}\ \ \ \ \ \ \ \ \ \ \ \ R^* = \frac{\color{red}{R}}{S_{C}\color{red}{L_H}} $$

Test of nonlinear sediment flux

Identify tectonic characteristics of landscapes

Understand variablilty of landscape properties

## More evidence for nonlinear sediment flux!

##

#### Detecting uplift and decay

#### Why do the Appalachians exist?

200 million years since uplift ceased

#### Why do the Appalachians exist?

Theory 1: Uplift is still happening, just slowly

Theory 2: Topographic rejuvenation in the Miocene

#### Evidence of topographic decay?

Tentatively supports the theory of Miocene rejuvenation

#### Topography has lots of information about process

Using only topographic data we can:

Falsify flux laws

Identify tectonics

#### The project you start isn't always the project you finish!