1. Watershed Assessment (ENSC 202)
Phase 2 – Step 6
The Rapid Habitat Assessment (RHA)
Extracted from Vermont ANR Stream Geomorphic Assessment Protocols Handbook - Introduction
ENSC 202 – 2004
Phase 2 Step 6 RHA

2. Objectives of the RHA
Determine if a stream is supporting or not supporting aquatic life
Characterize the existence and severity of impairment
Help to identify sources and causes of impairment
Evaluate the effectiveness of control actions and restoration activities
ENSC 202 – 2004
Phase 2 Step 6 RHA

3. High vs Low Gradient Streams
High gradient streams typically appear as steep cascading streams, step/pool streams, or streams that exhibit riffle/pool sequences (usually stream types A, B, and C). Most of the streams (outside of Chittenden County!) in Vermont are high gradient streams.
Low gradient streams typically appear slow moving and sinuous, and have less clearly defined riffles and pools and may even exhibit ripple-dune bed features (usually stream types E and sometimes C). Common in valley bottoms of the Champlain Valley.
Most of our stream reaches will be low gradient
ENSC 202 – 2004
Phase 2 Step 6 RHA

4. RHA 1 – Epifaunal Substrate / Available Cover
Reference condition
Poor condition
Keys
Quantity
Variety
ENSC 202 – 2004
Phase 2 Step 6 RHA

5. RHA 2 – Embeddedness Pool Substrate Characterization
Reference condition
Poor condition
Focus on riffles
High
Gradient
Keys
Type
Variety
Low
Gradient
ENSC 202 – 2004
Phase 2 Step 6 RHA

6. RHA 3 Velocity/Depth Patterns Pool Variability
Reference condition
Poor condition
High
Gradient
Low
Gradient
ENSC 202 – 2004
Phase 2 Step 6 RHA

7. RHA 3 Criteria Slow Fast Deep Shallow Small Large Deep Shallow
D > 1.5 feet (0.5 m)
V < 1 ft/sec (0.3 m/sec
V > 1 ft/sec (0.3 m/sec
Shallow
D <1.5 feet (0.5 m)
D < 1.5 feet (0.5 m)
Bed Features
Step
Riffle
Run
Pool
Glide
High
Gradient
Small
Large
Deep
W&L < ½ Wbkf
D > 3 feet
W&L > ½ Wbkf
Shallow
D < 3 feet
Keys
Even mix
Deep pools
Low
Gradient
ENSC 202 – 2004
Phase 2 Step 6 RHA

8. RHA 4 Sediment Deposition
Reference condition
Poor condition
Keys
Point bars
Mid-channel bars
Islands
Some of these are natural!
ENSC 202 – 2004
Phase 2 Step 6 RHA

9. RHA 5 Channel Flow Status
Reference condition
Poor condition
Typical flow alterations
hydropower
irrigation
public water supplies
snowmaking
recreation and flood control reservoirs
ENSC 202 – 2004
Phase 2 Step 6 RHA

10. RHA 6 Channel Alteration
Reference condition
Poor condition
Keys
Berms
Dredging
Straightening
Armoring (revetments)
ENSC 202 – 2004
Phase 2 Step 6 RHA

11. RHA 7 Morphological Diversity Sinuosity
Reference condition
Poor condition
High
Gradient
Low
Gradient
ENSC 202 – 2004
Phase 2 Step 6 RHA

12. RHA 8 Bank Stability Reference condition Poor condition
ENSC 202 – 2004
Phase 2 Step 6 RHA

13. RHA 9 Bank Vegetation Protection
Reference condition
Poor condition
Keys
Root binding capacity
Grass no good for banks > 0.5 m (1.5 ft)
Shrubs/trees no good for banks > 1.5 m (4.5 ft)
ENSC 202 – 2004
Phase 2 Step 6 RHA

14. RHA 10 Riparian Buffer Width
ENSC 202 – 2004
Phase 2 Step 6 RHA

15. RHA Score RHA = Σ(individual scores)/200 ENSC 202 – 2004
Phase 2 Step 6 RHA