Using ArcGIS to Assist in

Geomorphic Surface Mapping

Michael Bigsby

Tetra Tech, Inc.

June 30, 2016

Background

• ArcGIS was used to perform desktop mapping of

geomorphic surfaces of a stream valley

• Mapped surface data layers were edited on an iterative

basis to incorporate each dataset into the surface mapping

process

• Each line of evidence was evaluated independently using

serval tools and features of ArcGIS in order to distinguish

individual surfaces

Objective

• Demonstrate how GIS is used to develop a geomorphic

interpretation of stream valley

- Features of ArcMap used in mapping process

- Spatial Analyst

- 3D Analyst

- Analysis Tools

- Conversion Tools

The Approach

• Fluvial geomorphology:

The study of the origin

and evolution of stream-

related landforms

• A geomorphic surface is

an area formed by

similar physical factors

related to morphology

and time

• Fluvial systems are

complex and dynamic

The Approach

Layering of multiple datasets

Methods

• Multiple lines of evidence:

- Aerial photos (recent and historic)

- Contour lines

- Stream channel gradient

- Slope steepness

- Geomorphic setting

- Channel width

- Water depth

- Water velocity

- Land use

- Anthropogenic impacts (e.g. dams, bridges, channel straightening)

Methods

Use aerial photography to digitize stream channel

Methods

DEMs are processed using several Spatial

Analyst tools…

Methods

Methods

Methods

DEM + Contour lines + Hillshade

Methods

3D Analyst is used to create lateral cross-sections and

longitudinal profiles

Methods

3D Analyst

Methods

Methods

Reach 1

Reach 5

Methods

Methods

Methods

Results

Methods

Field confirmation of

desktop mapping

• GPS data can be

used to spot-check

the DEM

• “See” if mapped

surfaces match the real world

Conclusions

• Some limitations exist

- Quality of GIS data

- Typically requires many iterations to reach a level of

confidence in geomorphically complex areas

- Difficult to characterize small-scale variations

Conclusions

• Many benefits

- Allows detailed visualization of complex fluvial patterns

- Synthesis of multiple lines of evidence

- Key to developing a sampling plan

- Results can be refined with new data

- Refined with field-collected data

- As new data is incorporated, Spatial Analyst can be used to

perform time-series analysis

- Datasets can be used a inputs into hydrodynamic models with

the outputs of the models being displayed in ArcGIS