1 / 27

Watershed Assessment (ENSC 202)

Watershed Assessment (ENSC 202). Phase 1 – Steps 6-10 Extracted from Vermont ANR Stream Geomorphic Assessment Protocols Handbook - Introduction. Step 6 Floodplain modifications. 6.1 Berms and Roads 6.2 River Corridor Development 6.3 Depositional Features

ardice
Télécharger la présentation

Watershed Assessment (ENSC 202)

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. Watershed Assessment (ENSC 202) Phase 1 – Steps 6-10 Extracted from Vermont ANR Stream Geomorphic Assessment Protocols Handbook - Introduction ENSC 202 – 2004 Phase 1 Steps 6-10

  2. Step 6 Floodplain modifications • 6.1 Berms and Roads • 6.2 River Corridor Development • 6.3 Depositional Features • 6.4 Meander Migration / Channel Avulsion • 6.5 Meander Width Ratio • 6.6 Wavelength Ratio ENSC 202 – 2004 Phase 1 Steps 6-10

  3. Rationale for Step 6 • Streams need floodplains for adjustment • Development often constrains the floodplain • Floodplain constraint can increase stream power • Increased power can move larger particles, leading to degradation ENSC 202 – 2004 Phase 1 Steps 6-10

  4. Step 6.1 Berms and Roads • Rough percentages in the river corridor • Does not include crossings • Impact rating I-89 along Winooski River ENSC 202 – 2004 Phase 1 Steps 6-10

  5. Step 6.2 River Corridor Development • Houses, fill (including bridge and culvert fills), parking lots or other development • Impact rating ENSC 202 – 2004 Phase 1 Steps 6-10

  6. Step 6.3 Depositional Features • Un-vegetated ‘bars’ • Impact rating ENSC 202 – 2004 Phase 1 Steps 6-10

  7. Step 6.4 Meander Migration/Channel Avulsion • Best done by difference analysis with orthophotos • GIS or tracing on acetates • Consider errors in overlays • Impact rating High impact migration and avulsion ENSC 202 – 2004 Phase 1 Steps 6-10

  8. Step 6.5 Meander width ratio • Only certain reaches (step 2.10) • types C or E riffle-pool or ripple-dune reference types • narrow (NW) and unconfined (BD and VB) valleys • If straighten >50% belt width = channel width  MWR=1 • naturally confined and braided stream types • enter “0” for MWR • enter not applicable (“N/A”) for the impact rating • See Appendix H ENSC 202 – 2004 Phase 1 Steps 6-10

  9. Step 6.6 Wavelength ratio • Same restrictions as in step 6.5 • WLR = wavelength/channel width (2.8) ENSC 202 – 2004 Phase 1 Steps 6-10

  10. Step 7 Bed and Bank Windshield Survey • 7.1 Dominant Bed Form / Material • 7.2 Bank Erosion – Relative Magnitude • 7.3 Debris and Ice Jam Potential ENSC 202 – 2004 Phase 1 Steps 6-10

  11. Rationale & considerations for Step 7 • An opportunity to check validity of Phase 1 assessments before Phase 2 effort • Do advanced planning to limit drive time • Take care in doing assessments from bridges  bridge impact • Good opportunity to do some photo documentation ENSC 202 – 2004 Phase 1 Steps 6-10

  12. Step 7.1a Dominant bed form ENSC 202 – 2004 Phase 1 Steps 6-10

  13. Step 7.1b Dominant bed material ENSC 202 – 2004 Phase 1 Steps 6-10

  14. Step 7.2 Bank erosion – relative magnitude • Bank erosion • Bank heights Remember that some erosion is natural ENSC 202 – 2004 Phase 1 Steps 6-10

  15. Step 7.3 Ice/debris dam potential ENSC 202 – 2004 Phase 1 Steps 6-10

  16. Step 8 Stream Impact Ratings • 8.1 Impact Rating • High(2), Low(1), Not sig (0), Don’t know (0) • 8.2 Priority Rating • A tool available in the database reporting functions ENSC 202 – 2004 Phase 1 Steps 6-10

  17. Step 9 Stream Geomorphic Condition Assessment • 9.1 Channel Adjustment Process • 9.2 Reach Condition • 9.3 Reach Sensitivity ENSC 202 – 2004 Phase 1 Steps 6-10

  18. Step 9.1 PROVISIONAL channel adjustment processes This table is generated automatically by the database. See Appendices B and C Adjustment defined as score > 4 ENSC 202 – 2004 Phase 1 Steps 6-10

  19. ENSC 202 – 2004 Phase 1 Steps 6-10

  20. Channel Evolution Models (CEM) • F- and D-stage streams • unconfined, low gradient valleys where the streams are not entrenched • access to floodplain at 1-2 year flood stage • F-stage process: bed and bank is erodible • D-stage process bed and bank less erodible ENSC 202 – 2004 Phase 1 Steps 6-10

  21. F-stage CEM ENSC 202 – 2004 Phase 1 Steps 6-10

  22. D-stage CEM ENSC 202 – 2004 Phase 1 Steps 6-10

  23. Step 9.2a Reach condition score • Calculated by the database • Based on the 4 key adjustment processes • Calculated for each reach based on the worst adjustment process in the worst reach • Effectively a ‘bad’ to ‘worst’ scoring system ENSC 202 – 2004 Phase 1 Steps 6-10

  24. Step 9.2b – Reach condition score ENSC 202 – 2004 Phase 1 Steps 6-10

  25. Step 9.3 Reach sensitivity(Subjective) Considerations ENSC 202 – 2004 Phase 1 Steps 6-10

  26. Step 10 Like Reach Evaluation • Basically a simple sorting tool in the database • May help in selecting reaches for Phase 2 field work ENSC 202 – 2004 Phase 1 Steps 6-10

  27. Remember to do your QA/QC!! ENSC 202 – 2004 Phase 1 Steps 6-10

More Related