crjc mount ascutney local river subcommittee...2019/03/12 · mount ascutney local river...

CRJC Mount Ascutney Local River Subcommittee

Tuesday, March 12th, 2019 Windsor Welcome Center 7:00PM Minutes

Attendees

Plainfield Elise Angelillo Windsor

Plainfield David Taylor Windsor

Cornish Bill Gallagher X Weathersfield Howard Beach X

Cornish Colleen O’Neill X Weathersfield Nancy Heatley X

Claremont Springfield Bill Manner

Claremont Springfield Kelly Stettner X

Hartland Cordelia Merritt X Rockingham Thomas Hernon

Hartland Judy Howland X Rockingham Margaret Perry

Charlestown

Charlestown

Kristen Underwood (speaker) 7 Members of the public joined for the presentation Olivia Uyizeye (staff, UVLSRPC) Minutes

Working Towards Flood Resilience in our Communities – Kristen Underwood

Note: The regular MARS meeting was cancelled in lieu of the engaging speaker and subsequent conversation. The following are notes on that presentation, including a copy of the PowerPoint presentation attached at the end of these minutes.

Heatley opens the meeting by introducing the goals and activities of MARS. Heatley thanks guests for joining the reps in the presentation today. Stettner introduces the speaker – Kristen Underwood as a collaborator and someone who explores what rivers do.

Underwood begins by explaining that rivers are dynamic systems that move through space and time. Pictures are shown of the Ottauquechee River in 2011 at 2 different times – one at normal flow and one during a flood.

Rivers move not only water, but also sediments, large woody debris, trash, ice (subject to ice dams), and organic matter (feeds the food web). FEMA provides maps that analyze the risk of flooding to an area, however, these models can be inaccurate because they do not take into account erosion and other hazards that are a result of moving water.

In the New England region many utilities, farms, and homes lie in the river corridor. In the 1990s flooding prompted those in Vermont to dredge and armor the banks of rivers – a costly process that is not always effective management. How then do we give our rivers more room to move naturally?

VT performs a 3 phase assessment of their streams based on the science of fluvial geomorphology which allows them to categorize rivers into types.

Field crew does an inventory of the river, including river profile, bank erosion, substrate, etc

Determines any adjustment processes: 1) downward scour (can work its way upstream); 2) widening; 3) aggradation; 4) planform adjustments (can be seen through historical images, including those available on google earth, identifying river sections that tend to meander more than others)

These are all natural processes A “stable” river will have the same general slope, meander distance, etc, but stressor can accelerate the rates of these changes

Note that it can be hard to find good reference rivers, especially in the lowlands but not as much in the headwaters.

The assessment gets turned into River Corridor Plans in VT, making suggestions on how to maintain a balanced river. These plans identify stable, entrenched (often town centers), adjusting laterally (changing floodplains)

These plans can also identify river regions that can support expanded flood plain dynamics.

What can homeowners/community members do?

Know your backyard river. Stream stats gives you watershed information for the river of interest. Volunteers for a local river group for activities like water sample collection, cleanup, education, etc.

Look for opportunities to reconnect the river. Failing culverts, bridges, dams, etc. See something, share it. Town of Bristol is working to expand and preserve a meander belt width. This has included compensation to landowners for the area take out of production. This was also an inexpensive stormwater management strategy. Another strategy is planting buffers along stream banks (like willows that can be planted as wattles or stakes). These are great active engagement projects for various groups, including students of all ages. Another strategy is putting in root wads along the bank for stabilizations, habitat and sediment capture.

Engage in local planning and zoning. Many towns are accepting enhanced floodplain bylaws, river corridor easements, and restoration projects.

Q&A

Heatley asks about how to collaborate with dam owners along the CT and tributaries Also, what can be done to offset impacts when owners are not willing to collaborate? What can be done to remove unused dams when a very costly and culturally sensitive structure.

Underwood responds that “it depends”. Not all dams are bad or good – they can provide hydropower and flood control while others are complete inactive and in disrepair. Each situation has to be evaluated for its context. There are mitigation strategies such as fish ladders and water release. Dam removal can often be done with public/private partnerships. Contact the state, Trout Unlimited. There is also a photo technique to help visualize removal (Tom Schiff is recommended as a speaker).

Underwood – references a video in her slideshow that shows the use of a streamtable to help individuals visualize flooding impacts.

Attendee – Interested to learn more how things work holistically – connecting in with wetlands, forests, etc. Do we create plans that look into this complexity?

Underwood – Part 1 of the VT assessment is a watershed wide analysis, including soil, landcover, etc. NH also uses versions of these VT assessments with its own web based system. They have not covered the state as expansively as VT at this point but working towards it.

Heatley – Riparian buggers often require communications with homeowners. Any suggestions on how to communicate the importance of these buffers to those who buy property for the river view?

Underwood – Ultimately this is individual choice. Trees/shrub can stabilize and save the bank on that property and those downstream There are also ways to balance planting and maintaining river access and view (even if smaller)

Uyizeye – How severely do undersized culverts impact flooding

Underwood – Undersized culverts can jam up with debris, wash over and even blow out the road. USFS replaced many undersized culverts before Tropical Storm Irene. These survived the storm while those that were not replaced often did not. It is more costly to upsize for that moment, however, savings occur by replacing less and therefore lasting longer. It is less costly to be proactive, but it is hard for those reliant on FEMA funds (that now pay up to 75% of culvert replacements and now allow upsizing).

Howland – Does a lot of work with stream tables as a way to get acquainted with river dynamics, including road crews and students. One will be up at the upcoming Flavors of the Valley event on April 7, 2019, 11am-30m at the Hartford High School.

Beach – Storms are likely to increase in intensity and decrease in duration that could create a higher frequency of failing structures.

Attendee – Windsor has created a floodway adaptation program call the Windsor Improvement Corporation to help those living in the floodway.

Heatley thanks Underwood for her presentation and closes the event.

Minutes respectfully submitted by Olivia Uyizeye.

Working Toward Flood Resilience in our Communities

Mount Ascutney Local River Subcommittee of the Connecticut River Joint Commission

March 12, 2019

mainerivers.org

swimming

Slide from VT Agency of Natural Resources

FEMA maps denote structures at risk of inundation flooding….

Slide from VT Agency of Natural Resources

… but do not address erosion hazard flooding risk.

Mansfield Heliflight

Mansfield Heliflight

• Led to a new river management paradigm

• Give the river more room

• Floods of 1990s very costly to the State of Vermont - $60M

• Traditional approaches unsustainable, especially in light of changing climate

Evolution of River Management in VT

Slide elements from VT ANR

Ecological

Integrity and

Fish & Wildlife

Resource

Water Quality

and Quantity

Public Safety

and Property

Protection

Slide from Mike Kline, VTANR

Ecological

Integrity and

Fish & Wildlife

Resource

Water Quality

and Quantity

Public Safety

and Property

Protection Stream

Equilibrium &

Floodplain

Function


Fluvial Geomorphology

Fluvial Geomorphology

Running water processes

EarthStudy of shapes

VT Protocols for Stream Geomorphic Assessment

Cross Sections

VT Protocols for Stream Geomorphic Assessment

Dominant Substrate Size (D50)

Assign Stream Type

D4-braided

C4b-riffle/pool C4-riffle/pool E5-dune/ripple

A1-cascade B3c-step/pool B2-step/pool

Degradation (Incision)Knickpoint (can migrate upstream and undermine infrastructure)

Unless Arrested by a Grade Controlstructure (e.g., bedrock)

Downward scour into the channel bed

• Undercut banks, scour-exposed roots• Steep riffles or headcuts (i.e., knickpoints)

Dominant Adjustment Processes

Pictures from VTANR Rivers & Roads training manual

Widening

• Oversteepened banks exceed critical height for the material

• Banks collapse by slumping, block failure, piping, exacerbated by erosion at the toe of the slope.

• Trees lean and fall into the channel from both banks.


Aggradation

Build up of the channel bed through deposition


• Unvegetated bars• Steep bar faces• Mid-channel bars

Picture left from VTANR Rivers & Roads training manual

Planform Adjustment

• Over-widening and aggradation lead to cut banks and meander migration

• Analysis of historical aerial photographs can reveal significant planform shifts over time.


Sediment Regime Departure

River Corridor Plans

StableEntrenched

• Define Current Condition

• How the Reach is likely to evolve or adjust in Future

• Identify Projects and Practices that will Reconnect the River and support a return to a more balanced, stable form

Adjusting Laterally



StableEntrenched


• How the Reach is likely to evolve or adjust

• Identify Projects and Practices that will Reconnect the River and support a return to a more balanced, stable form Ludlow

Proctorsville

Cavendish

Adjusting Laterally



StableEntrenchedAdjusting Laterally


• How the Reach is likely to evolve or adjust

• Identify Projects and Practices that will Reconnect the River and support a return to a more balanced, stable form Ludlow

Proctorsville

Cavendish

Possible Attenuation Assets upstream of

village centers

What can I do to support balanced and connected rivers?

1. Know your backyard river

1. Know your backyard river…what stream type it is and

how prone to adjustment it is

1. Know your backyard river…by consulting assessment data and


Mill Brook watershed, NH

1. Know your backyard river …the watershed that contributes to it.

USGS Streamstats

1. Know your backyard river …and the water quality.

Black River Action Team



2. Look for opportunities to reconnect rivers

2 - Look for Opportunities to Reconnect Rivers

From 2015 to 2017, more than 1,200 river projects were completed to reconnect rivers or maintain river connections in Vermont

Federal Interagency Stream Restoration Working Group

http://freevtrivers.org/videos/adapting-changed-climate-dams-flooding/

Removal of Mill Brook DamWest Windsor, VT

2 - Look for Opportunities to Reconnect Rivers - Longitudinally

Replace Undersized Stream Crossings that also block passage of fish and

other critters.

2 - Look for Opportunities to Reconnect Rivers - longitudinally

• CRP/CREP –- compensated landowner for lands taken out of production- planted entire meander belt width

• River Corridor Easements (2): -VT River Conservancy

• Town: Fluvial Erosion Hazard language and planning maps

River Corridor Protection

Sept 9, 2011

2 - Look for Opportunities to Reconnect Rivers - laterally

Restore Buffers along Stream Banks

• Willow wattles, stakes

Volunteers from Middlebury College Alpine Ski Team, New Haven River Anglers, Bristol Conservation Commission




2. Look for opportunities to reconnect rivers

3. Engage in local planning and zoning – strategies for avoiding & mitigating flood losses

77 / 251 Towns with River Corridor or

Enhanced Floodplain Bylaws

45 Communities with completed River Corridor

Floodplain Restoration Projects

90 River Corridor Easements Channel management rights purchased to

attenuate flows at key watershed locations



Contact InfoKristen Underwood, PG, PhDResearch Assistant ProfessorCivil & Environmental EngineeringUniversity of [email protected]

Questions ?

crjc mount ascutney local river subcommittee...2019/03/12 · mount ascutney local river...

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