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Geoprocessing Model to Calculate Side Slopes for Pipeline
Construction
Gene LohrmeyerSenior GIS AnalystGeoEngineers, Inc.
From <http://www.wikipedia.org/>
Overview
• What are side slopes and why do we care
about them when planning a pipeline route?
• Workflow for identifying side slopes before
and after.
• Geoprocessing model for identifying side
slopes.
Side Slope
What is a side slope?
A slope at a given horizontal:vertical ratio or %
slope that is being traversed across.
Level Terrain
Side Slope
Side Slope
Side Slope
Side Slope
Side Slope Considerations
• More hazardous working and operating conditions.• Severe erosion and landslide potential.• Workspace needed increases.• Specialized equipment• Production costs increase as terrain roughness and slope %
increases.
“The presence of rough terrain and/or side slope negatively impacts every stage of pipeline construction, from ‘clear-grade’ to ‘clean-up’, and can be estimated by impacts to overall ‘lay-rate’ or production.”
From Bill Delancy, Gulf Interstate Engineering
Side Slope Considerations
Terrain Approximate Production Impact
0-5% slope in rolling terrain 10%5-10% slope in rolling terrain 15%5-10% slope in rough, mountainous terrain 20-25%
10-20% slope in rolling terrain, no rock 20%
10-20% slope in rough, mountainous terrain with rock 30%
20-30% slope in rolling terrain, no rock 40%
>30% slope in rolling terrain, good access, no rock 45%
>30% slope, in mountainous terrain, limited access, rock impact
50-75%
Client Requirement
Identify areas of potential steep side slopes so client can either avoid or account for when planning the pipeline route.
Workflow - Before
Workflow - Before
125 miles450+ miles
Workflow – Before Issues
• Subjective, especially with more than one geologist or engineer weighing in.
• Time consuming for everyone involved.• Hand edits • Digitizing • Back and forth • Estimated lengths
• Increased cost to the client.
There is a better
way with GIS!
Workflow – Now
Side slope definition:• Any route segment with the slope fall line intersecting between 45
and 135 degrees.
Side Slope Window
Side Slope Window
Workflow – Now
Side slope definition:• Any route segment with the slope fall line intersecting between 45
and 135 degrees.
Workflow – Now
Side slope definition:
Route Segment
Slope Fall Line
45 – 135 degree window
Side Slope = True
Workflow – Now
Side slope definition:
Route Segment
Slope Fall Line
45 – 135 degree window
Side Slope = False
Workflow – Now
Two pieces of information needed to calculate fall line bearing along a segment:• Aspect of slope.• Bearing of segment.
In Field Calculator
Workflow – NowGeneral Side Slope Calculation Workflow
Workflow – Now
Buffer route150’
Generate aspect from DEM
Convert aspect raster to polygon
Intersect aspectpoly and route
Calculate route segment bearing
Workflow – Now
Buffer route150’
Generate aspect from DEM
Convert aspect raster to polygon
Intersect aspectpoly and route
Calculate route segment bearing
Fall Line Bearing Route Segment Bearing
Workflow – NowRoute Segment Sideslope Calculation
Buffer route150’
Generate aspect from DEM
Convert aspect raster to polygon
Intersect aspectpoly and route
Calculate route segment bearing
Calculate side slope true or false
Workflow – NowRoute Segment Sideslope Calculation
Bearing = 45o
Bearing1 = 90o
Bearing2 = 180o
Bearing3 = 270o
Bearing4 = 360o
Sideslope = trueSideslope = false
Buffer route150’
Generate aspect from DEM
Convert aspect raster to polygon
Intersect aspectpoly and route
Calculate route segment bearing
Calculate side slope true or false
Workflow – NowGeneral Side Slope Calculation
Workflow – Now
Generate slopeFrom DEM
Reclassify Slope
Convert slope grid to polygon
Intersect side slope segments and slope poly
Workflow - Now
Geoprocessing Model
• Workflow works but can be labor intensive to do each step by hand in GIS.
• Need a way to automate the process.• Geoprocessing model fits the need.
What is Geoprocessing?
• Allows you to automate GIS tasks and perform spatial analysis and modeling.
• Everything in the toolbox can be used in a geoprocessing model.
• Can create your own toolboxes and scripts.
Geoprocessing Model
Geoprocessing Model
Slope calculation, classification and conversion to polygon.
Buffer route and clip digital elevation model to buffer.
Aspect calculation, segment bearing calculation, side slope calculation.
Buffer side slope segments, calculate areas.
• Model allows GeoEngineers to quickly calculate
steep side slope areas for many miles of pipeline
in hours vs days.
• Model is reproducible and not based on
subjective expertise.
• Model is scalable
• Professional expertise and model can be used as
checks against one another.
Geoprocessing Model
Example Deliverables
Example Deliverables
Example Deliverables
Next Steps
• Make tool easier to use - Expose parameters.• Geoprocessing service• Github
Conclusion
• Discussed what side slopes are and why we care about them when planning a pipeline route?
• Looked at workflows for identifying side slopes.
• Geoprocessing model for identifying side slopes.
Contact
• Gene Lohrmeyer | GeoEnginers Senior GIS Analyst
• 425.861.6000
Thank You!
