Stream Geomorphic Assessment of Allen Brook Jarrett Arthur, Amy Myers Shea Hagy, Mike McDonald

Allen Brook Watershed drains 12 sq. miles Flows into Winooski after meeting Muddy Brook

Characteristics of Impairment Presence of pathogens High concentration of suspended solids Bank failure, erosion Lack of adequate riparian buffer zone Channelization leading to decrease in natural stream hydrological features such as pools and riffles

Methods Phase One Steps Phase Two Steps Rapid Geomorphic Rapid Habitat Assessment Assessment 2.1 Elevation 5.2 Bridges-Culverts 2.2 Valley Length 5.3 Bank Armoring 2.3 Valley Slope 5.4 Channel Modification 2.4 Channel Slope 5.5 Dredging History 2.5 Sinuosity 6.1 Berms and Roads 2.6 Watershed Size 6.2 River Corridor Development 2.7 Channel Width 6.3 Depositional Features 2.8 Valley Width 6.4 Meander Migration 2.9 Confinement 6.5 Meander Width Ratio 2.10 Stream Type 6.6 Wavelength Ratio 3.1 Alluvial Fan 7.1 Dominant Bed Form and Material 3.2 Grade Controls 7.2 Bank Erosion/Bank Height 3.3 Geologic Materials 7.3 Ice and Debris Jam Potential 3.4 Valley Side Slopes 8.1 Impact Rating 3.5 Soil Properties 8.2 Priority Rating 4.1 Watershed Land Cover 9.1 Channel adjustment Process 4.2 Corridor Land Cover 9.2 Reach Condition 4.3 Riparian Buffers 9.3 Reach Sensitivity 4.4 Ground Water Inputs 10 Like Reach Evaluation 5.1 Flow Regulation 6.1 Epifaunal Substrate/ Available Cover 7.1 Channel Degradation (Incision) 6.2 Embeddedness 7.2 Channel Aggradation 6.3 Velocity/Depth Patterns 7.3 Channel Widening 6.4 Sediment Deposition 7.4 Change in Planform 6.5 Channel Flow Status 6.6 Channel Alteration 6.7 Frequency of Riffles/Steps 6.8 Bank Stability 6.9 Bank Vegetative Protection 6.10 Riparian Vegetative Zone Buffer

Reach Designation

M3T3.11 Culvert Dense Sprawly Surroundings Buffer Reclaimed Field Grass Golden Rod Deep Plunge Pool Braided Channel

M3T3.10 Buffers Widen Braiding Ends Cobbles and Boulders Bank Failure provides Coarse Woody Debris Channel migration Undercutting Point bars Channel Widening

M3T3.9 Transition Zone Degrad. and Aggrad. Present Throughout Banks Flat and Broad Wetland Area on Lower Portion of Right Bank Left Bank Supports Larger Trees Beds Still Dominated by Cobbles but Embeddedness is Occuring Hemlock Beech Maple

M3T3.8 First Impaired Reach Area Surrounding the right bank is wetland There is a large pond within 20 feet of the stream bank Less Trees throughout reach Right Buffer Gets Thinner Downstream Old Farm Field Creeping in on Left Bank Embeddedness Occurs Throughout Erosion occurrs on the outside of meanders. While they begin with beech and hemlock, the dominant trees gradually switch to willow.

M3T3.7 Dramatic Deterioration From Previous Reach Buffers become nonexistent land appears to have been cleared for farm pasture or crop field grass is dominant species The right bank is very wet and even has intermittent hydric soils. Willow Grows Thinly in the Stream Channel Streambed is Sand Evidence of Head Cutting Exists Incision is Dominant Force Right Bank has Some Hydric Soils

M3T3.6 Final Assessed Reach Begins and Ends at a Road Crossing with a Culvert Surrounding Landscape is Flat Reach is Deeply Incised Broad Meander Migration Occurring Streambed is Mostly Sand only Broken by Litter Prevailing Land use is Suburban Residential Development Prior to development, farmland predominated The resulting ground cover is uniform field grasses.

Results Figure 1. Rapid Habitat Assessment of impaired reaches compared to the attainment reaches – Allen Brook, 2004.

Figure 2. Rapid Geomorphic Assessment of impaired reaches as compared to attainment reaches – Allen Brook, 2004.

Figure 3. Rapid Habitat Assessment compared to the watershed condition on all six reaches – Allen Brook, 2004.

Figure 4. Rapid Geomorphic Assessment compared to the watershed condition on all six reaches – Allen Brook, 2004.

Figure 5. Rapid Habitat Assessment scores compared to the Rapid Geomorphic Assessment scores for all six reaches – Allen Brook, 2004. R2=.9529

Conclusions Our impaired reaches are significantly more degraded than our attainment reaches both in terms of geomorphic processes and habitat suitability The degree of impairment in all of our reaches increases in severity the further downstream the reach is located. Current land development surrounding Allen Brook combined with the historic use of land for agricultural purposes has caused the health of the brook to decrease and the abundance of native aquatic life to suffer. Assessment of stream condition using the ANR stream geomorphic protocols correlated to assessment using biocriteria.

Recommendations The implementation of soft engineering to stabilize failing banks may be able to reduce further degradation and erosion. The restoration of a riparian buffer of adequate width will help reduce runoff volume, velocity, increase nutrient retention, provide shading, and habitat. Best Management Practices (BMPs) will help reduce the detrimental effects of surrounding agricultural and residential land.

Acknowledgements Special thanks to Bill Gill in the library for all the help, especially at ridiculous hours of the night, and to Breck Bowden for advice and guidance throughout the whole process.