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

ENSC 202 – 2004 Phase 1 Steps 6-10 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 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 HAppendix H

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

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

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

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

ENSC 202 – 2004 Phase 1 Steps 6-10

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

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

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

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

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