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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
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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
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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
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RHA 1 – Epifaunal Substrate / Available Cover
Reference condition Poor condition Keys Quantity Variety ENSC 202 – 2004 Phase 2 Step 6 RHA
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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
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RHA 3 Velocity/Depth Patterns Pool Variability
Reference condition Poor condition High Gradient Low Gradient ENSC 202 – 2004 Phase 2 Step 6 RHA
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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
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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
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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
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RHA 6 Channel Alteration
Reference condition Poor condition Keys Berms Dredging Straightening Armoring (revetments) ENSC 202 – 2004 Phase 2 Step 6 RHA
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RHA 7 Morphological Diversity Sinuosity
Reference condition Poor condition High Gradient Low Gradient ENSC 202 – 2004 Phase 2 Step 6 RHA
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RHA 8 Bank Stability Reference condition Poor condition
ENSC 202 – 2004 Phase 2 Step 6 RHA
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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
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RHA 10 Riparian Buffer Width
ENSC 202 – 2004 Phase 2 Step 6 RHA
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RHA Score RHA = Σ(individual scores)/200 ENSC 202 – 2004
Phase 2 Step 6 RHA
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