Embed Size (px)
Citation preview
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
