sheffield brook floodplain restoration & culvert replacement
TRANSCRIPT
Sheffield Brook Floodplain Restoration & Culvert
Replacement
Kristine M. Baker, P.E.Fuss & O’Neill, Inc.
Presentation for
Connecticut Association of Flood Managers Conference
October 25, 2017
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Agenda
• Project Site• Existing Conditions• Project Objective• H&H Modeling• Existing Conditions Results• Proposed Project• Expected Results
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Project Site
Project Site
Watershed Area
Hartford, CT
Old Lyme, CT
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Existing Conditions
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• Problem: Lack of floodplain storage and undersized culvert causing interior flooding in neighborhood
• For example, an inland event in March 2014 created significant flooding from a recorded 4.7-inch storm; approximately a 10-year return period
Interior Flooding Issues
Flooding on Sea Spray Avenue (March 30, 2014)
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1. Restore Floodplain– Improve ability to store and convey and floodwaters
2. Increase Capacity of Culvert Under Beach– Double Capacity of Existing 36” Pipe– Reduce Shoaling of Pipe
3. Tidal Controls for Coastal Events– Reduce potential for storm surge to flood neighborhood
Keys to Reducing Flooding
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Hydrology & Hydraulics ModelingHydrology Model Schematic Hydraulics Model Schematic
(HydroCAD) (HEC-RAS)
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Existing Conditions Model
0 200 400 600 800 1000 1200 1400 1600-2
0
2
4
6
8
10
12
Main Channel Distance (ft)
Ele
vatio
n (ft
)
W
W
2.1
5 6 7 8 9 10 11 12 13 14 15 16
1-YEAR FLOOD
2-YEAR FLOOD
10-YEAR FLOOD
100-YEAR FLOOD
Existing Conditions Maximum Water Surface
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Existing Conditions Model Results1-year Flood 2-year Flood
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Existing Conditions Model Results10-year Flood
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• Major modeling conclusions are: – The 36-inch culvert causes backwater under all the modeled
storm event scenarios– Floodwaters overtop the culvert and flow as overland flow
over the surface to the beach under the 10- and 100-year flood events
– The backwater from the culvert begins to influence the water surface elevations near Maple Avenue
– Flooding north of Maple Avenue is not influenced by the culvert, so will require addition of floodplain storage to reduce water surface levels
EC Modeling Conclusions
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1. Restore Floodplain– Improve ability to store and convey floodwaters
2. Increase Capacity of Culvert Under Beach3. Install Weir Boards to Reduce Tidal Flooding
Proposed Project
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Floodplain Restoration
1. Two-Stage Channel Design2. Meandering Stream through created Floodplain3. Removal of 5,500 CY of previously placed fill4. Bioengineered Stabilization – Root wads and plantings
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Two-Stage Channel Design
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Culvert and Tidal Control Improvements
1. Twin 36” Culverts2. Junction Box for Weir
Boards3. Open Channel with
groins and revetment
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Weir Board Junction Box
PLAN VIEW
FRONT VIEW
SIDE VIEW
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Expected Results1-year Flood Event 2-year Flood Event
PROPOSED
EXISTING
PROPOSED
EXISTING
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Expected Results
PROPOSED
EXISTING
10-year Flood Event 100-year Flood Event
PROPOSED
EXISTING
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• Kris, I need the updated flood modeling results
Expected Results
10-year FloodExisting
Water Surface
Ground Surface
Proposed Water
Surface
Location of Maple Ave
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• Junction Box construction
Construction Photos
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• Groin
• Bilco Doors
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• Upstream Headwall
• View Looking downstream
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Kristine Baker, PESenior Project EngineerFuss & O'Neill, Inc.146 Hartford Road, Manchester, CT 06040860.646.2469 [email protected] www.fando.com
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