1 / 25

Detention/Retention Strategies and Techniques

Detention/Retention Strategies and Techniques. URBDP 598G – Floodplain Management December 8, 2008 Chris Scott Pat Keys. Goal – Flatten hydrograph and limit peak discharge during flood events.

rich
Download Presentation

Detention/Retention Strategies and Techniques

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Detention/Retention Strategies and Techniques URBDP 598G – Floodplain Management December 8, 2008 Chris Scott Pat Keys

  2. Goal – Flatten hydrograph and limit peak discharge during flood events Objective – Develop techniques to define and locate areas for potential detention/retention upstream of vulnerable areas Objective – Document GIS procedure for site location.

  3. Definition of Sites Investigated • Typical conditions must include appropriate land use (i.e. vacant lands, resource lands, or privately held lands set aside for mitigation) • Large depressions over permeable soils (retention) • Large, flat (<2% slope) areas available for over land flow (detention) to increase friction. • Targeted areas for in-stream and stream-bank wier/LWD friction and diversion installations.

  4. Retention • Large depressions over permeable soils • Requirements: • Areas accessible, with minimum construction costs, to river at bank full state • Permeable soils to facilitate aquifer re-charge and further improve downstream discharge rates

  5. Detention • Overland flow area to increase friction. • Requirements: • Large area (>5 acres) accessible with minimum construction to river in bank-full condition. • Good vegetation cover to facilitate frictional retention of river flow. • Permeable soils to facilitate aquifer re-charge and further improve downstream discharge rates (less important for this type)

  6. Friction/ Retention • Targeted areas for in-stream and stream-bank wier/ LWD friction and diversion installations. • Requirements: • Large non-vulnerable upstream area for increased water height and flooding. • Natural bank width with a shallow drop in river elevation (areas with significant braiding may be ideal).

  7. GIS Process

  8. GIS Process – Site Selection

  9. GIS Process – Raw LiDAR

  10. GIS Process – Hillshade

  11. Slope Analysis

  12. GIS Process – Percent Slope

  13. GIS Process – Classed Slope

  14. GIS Process – Classed Slope (polygon)

  15. GIS Process – Aerial w/ Slope (clipped to channel mig. zone)

  16. GIS Process – Hillshade w/ Slope

  17. GIS Process – Landuse w/ Slope & Channel Migration

  18. Hydro Analysis

  19. GIS Process – Flow Direction & Accumulation

  20. GIS Process – Reclassify Accumulation, to Polygon

  21. GIS Process – Soils with Very Good Infiltration

  22. GIS Process – Intersect Soils with Slope

  23. GIS Process – 37 Acres of infiltration

  24. GIS Process – Infiltration and Landuse

  25. Conclusions & Recommendations Process is relatively simple In study area, ideal detention and retention areas were rare; may be characteristic of region Significant amount of “37 acres of suitable infiltration” is likely currently streambed Instream frictional structures with upstream “safe-fail” floodable areas

More Related