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

#### Not a solo effort

And many others...

#### 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?

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?

Little spatial variation

Sensitive to channel network

Doesn't account for channel width

Underestimates hillslope length

#### Flow routing?

• Measure hillslope length as a flow path

• Connect ridges to channels

#### Flow routing?

Can be applied at a fine spatial scale

Accounts for local topography

Not subjective

## This data means we can test sediment flux laws

#### Sediment flux

• Volume of sediment transported on a hillslope per unit area in a period of time

• Sediment flux controls:

• Geometry of hillslopes

• Landscape response to climate and tectonic forcing

• Landscape evolution modelling

#### Topography is consistent with nonlinear sediment flux

• Demonstrated at a landscape scale

• Can be applied anywhere

• First test that relies only on topographic data

• Supports Roering's model

## 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!

#### 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

## Conclusions

#### Topography has lots of information about process

Using only topographic data we can:

Falsify flux laws

Identify tectonics

#### We need reproducible methods to exploit this information

lsdtopotools.github.io