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Cori Cox and Jeff Corns developed this outstanding presentation.
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GIS for Drainage AssessmentAndrew Harrison, GISP Business Development ManagerThe Schneider Corporation(317) 826-7393 [email protected]
Overview
• Generating watershed from GIS data
• Use of calculation software to assess drainage districts with Parcel, Watershed & Soils Layers
Accuracy…
• Fancy software does not equal accurate data
• Additional data layers will only be as accurate as basemap
• Parcels must be maintained and up-to-date through a known date– almost all GIS layers will refer back to
ownership information (in local government)
Watersheds of the Past?
Software
• ESRI– ArcGIS/ArcInfo– Spatial Analyst– Hydrology Modeling Extension
Contours – 2’ Seamless
Linear Stream Features
Elevation Raster
Flow Direction Raster
Flow Accumulation Raster
Raster Streams Layer
Watershed Rasters
Assumptions and Obstacles:
• 3 things to know about drainage (assumptions)– Water runs downhill
• Water drains into streams
– Payday is Friday– The boss is a jerk!
• Obstacles– “Sinks” and “Peaks”– Culverts
“Fill” Process for Sinks and Peaks
Streams at Culverts
Zoomed Stream Elevation Raster
“Burning” in the Streams
Watershed Generation Process
• Hydrology Modeling extension is used to “burn in streams” and build watersheds using raster images created from contour data
• Computer generated watersheds are merged/attributed to match County’s existing tiered administrative watershed system
Threshold = 500 Watersheds
Threshold = 5000 Watersheds
Remember these?
Tiered Watersheds
Watersheds
Tiered Watersheds
SubWatersheds
Tiered Watersheds
Subsof Sub
Watersheds
Tiered Watersheds
Subsof Subs
of SubWatersheds
Tiered Watersheds
Subsof Subsof Subsof Subs
Watersheds
What can I do with this watershed data?
• Provide greater accuracy to what was originally a poor data source– Hand drawn maps– On-screen digitized
• More equitable assessment for drainage– Geogear draincalc
Draincalc Overview
• A tool to utilize watershed data
• Allows drainage officials to quickly, accurately create the assessment
• Utilizes the geoprocessing functionality of ArcGIS– Meant to allow non-GIS people to benefit from
GIS
Tiered Watershed Layer
Watershed/Parcel Overlay
Watershed/Parcel Intersect - Lower
Watershed/Parcel Intersect - Upper
Watershed/Parcel/Soil Intersect
Range of Watershed Assessment Options
• Flat rate per benefited acre
• Percent of total (benefited acres)
• Setting minimum assessment amount(s)
• Additional assessment options– Soils– Parcel class/landuse– Distance from hydrological features– Any customization you come up with
Individual Watershed Projects
Defined Watershed Project
Proportion of total - values
Create Assessment Methods
Apply Assessment Rule Selections
Reports
Hearing Notice
Print Assessment Schedule
Summary
• How is this useful in the local government office?– Using GIS we were able to work from only
contours and parcels– Generate watersheds– Calculate assessments for those watersheds– Print hearing notices– Mail merge to labels (by watershed)
Customizable Assessment Methodology
Customizable Assessment Methodology
Benefits
• What benefits are gained from using GIS for these tasks?– More accurate watersheds– More equitable assessment– Speed and efficiency
Thank you!
Presenter: Andrew Harrison, GISP Business Development ManagerThe Schneider Corporation(317) 826-7393 [email protected]