Urban Watershed Delineation: Incorporation of Storm Sewer Networks

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Urban Watershed DelineationIncorporation of
Storm Sewer Networks

• James Bornemann
• Undergraduate Student
• Dept. of Geodesy and Geomatics Engineering
• University of New Brunswick

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Background

• Fredericton Area Watersheds Association (FAWA)
• Community based monitoring and research
• City of Fredericton
• Population 50,000
• Environmental management by watershed
• Socioeconomic and biophysical conditions
• Need Accurate watershed boundaries

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The City of Fredericton
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Social Ecological Conditions
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Previous Delineations

• New Brunswick DELG small scale delineation
• Wade MacNutt
• Local scale
• Combined automatic and manual method

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Storm Sewer Networks

• Are storm sewer networks significant to
  watershed delineations?
• Historical Evidence
• Ditch to divert headwaters of the swamp
• 155 acres for development
• Unknown location of early pipes
• Size vs. land use of area

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Historic Map The Swamp
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Watershed Delineation Methodology

• Based on Digital Terrain Model (DTM)
• Analyze topological relationships to model
  hydrological processes
• Assumption Surface Flow Only

Digital Terrain Model
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Topographical Watershed Delineation
Filled DTM
Flow Direction
Accumulation Grid
Generated Streams
Identify Outlets
Watershed Delineation
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Storm Sewer Delineation
Delineate Catch Basin Watersheds
Identify Storm Sewer Network

• Other Considerations
• Roads
• Other Drainage Networks

Final Delineation
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Watershed Comparison
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Types of Watersheds

• 3 Types of Watersheds
• Urban-Topographic
• Composite
• Shared

Maps of the 3 types
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Accuracy

• Process vs. Accuracy
• Precision of elevation data
• /- 10 ft. Vertical
• lt100 ft. Spacing of Elevation Data

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Environmental Management Application

• Require good information to make good management
  decisions
• Overlay watersheds and land use to help
  determine cause and affect
• Corbett Brook Watershed Management Example

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Corbett Brook Land Use
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Summary

• Methodology for delineating urban watersheds
  with storm sewer networks
• Storm sewer networks can significantly alter
  watershed boundaries
• Accuracy must be considered
• Land use of additional area can be as important
  as the increase in area

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Questions?

• Contact James Bornemann, d191d_at_unb.ca