1. Utilizing Automated Tools in ArcGIS
Accuracy Assessment of Methods for Quantifying the Upper Virgin River Watershed Basin
Utilizing Automated Tools in ArcGIS
November 2004

2. Data Background
In 2001 intensive research began assessing the health of the Upper Virgin Watershed
OBJECTIVES:
Baseline assessment
Create an archive of digital resources (GIS)
Current health assessment (digital & field collected)
Package data analysis in a GIS querying tool for water managers
GISWR
Project

3. GISWR Term Project
Utilize ArcHydro Terrain Processing tools as a secondary method to compare against methods and results from the Upper Virgin River Watershed Analysis project – compare and contrast differences
1) Location
2) Terrain
3) Process

4. OBJECTIVES
Accuracy assessment of methods: comparing streams, catchments, and DEM conditioning created using automated tools from ArcGIS, with those delineated from low elevation aerial flights.
Dual site comparison: results from highly varied terrain and extreme vertical relief (DEM investigation)
Quantitative & qualitative evaluation – prevention of cost prohibitive data investigation
SUMMARIZE
Summary of methods & analyze differences
Suggest implications of those differences
and what they mean to GIS data processing

5. Southwestern Utah, Washington County
Geographic Location
Southwestern Utah, Washington County

6. Process Steps Data Acquisition Site Selection (2)
Connectivity
Representative (digitally)
Scale
Terrain Processing (ArcHydro Tools)
Results (site comparisons)
Drainage Density
Inclusions/Exclusions
Scale, Processing
Quantitative & Qualitative Evaluation
Processing
Cost Perspective
Time Investment

7. 2.) Site Profiles Question….How does terrain processing
handle a flat watershed vs. a watershed with
extreme vertical relief?

8. Site-1
Aerial Photos
of red frames above
Relatively flat terrain along river corridor, connective, representative, 10m cell size
Elevation range:
min = 736 m (3513 ft)
max = 1800 m (9427 ft)
mean = 1278 m (4191 ft)
Stream/drop and buffer parameters set to 10/10/5 for AgreeDEM
Expected results:
1% threshold rule should apply
resulting streams should be comparable to aerial digitized streams
catchments should be consistent, connective, and representative of the landform

9. Site-2 Terrain is not flat along river corridors, disjointed landforms
Elevation range:
min = 1071m (3513 ft)
max = 2874m (9427 ft)
mean = 1972 m (6469 ft)
Stream/drop and buffer parameters set to 10/10/5 for AgreeDEM
Expected results:
1% threshold will not apply, toggling stream threshold will be required
resulting streams may not match aerial delineated and digitized streams
difficult to define streams and catchments across natural barriers of extreme relief

10. AgreeDEMs shown with normalized color scale
3.) Terrain Processing
AgreeDEMs shown with normalized color scale

11. Results from DEM Reconditioning using the
Agree Method

12. 3a)Terrain Processing – Result 1 Agree & Fill
(ABS[[orgDEM/AgreeDEM]-1])
Agree
Interpolated Elevation Pixels
Burning & Fencing, Fill Sinks
In blue & green, pixels that have changed from their original values
% change
km2
count
Driving values for ArcHydro Terrain Processing
Retest with natural barriers set to NODATA
Prevention of computations
(ABS[[orgDEM/FillDEM]-1])
Fill Sinks

13. 3b)Terrain Processing – Result 2 Stream Definition & Catchments
Stream definition occurring across vertical boundaries or natural barriers?
Toggle stream threshold
Catchments occurring across vertical boundaries or natural barriers?
Compare against low elevation aerial photography
Stream Definition
Catchments

14. In Process…. 4.) Results Summary Data Acquisition Site Selection (2)
Connectivity
Representative
Scale
Terrain Processing
Results (site comparisons)
Drainage Density
Inclusions/Exclusions
Scale, Processing
Aerial Comparison
Quantitative & Qualitative Evaluation
Comparative Processing
Cost Perspective
Time Investment
In Process….

15. 5.) Quantitative & Qualitative Evaluation
In Process….
Toggling of Stream Thresholds, stream/drop ratio and buffering for best watershed representation