AOP and FishXing Case Studies

John Hatt Creek

Corner Baffle Retrofit

Case Study Contributor:
Sebastian Cohen P.E., California Dept. of Transportation

Location
Navarro River Watershed, Northern California, USA. MAP

Project Type

  • Culvert Rehabilitation with Metal Insert
  • Corner Baffle Retrofit
  • Hydraulic Design
  • Placement of Concrete Weirs Below Outlet

Pre-project Conditions

  • 5.5 ft (1.7 m) diameter CSP, 172 ft (52.4 m) long, at 2.4% slope
  • Culvert distorted (out of round) and deteriorating
  • Culvert bottom lined with concrete
  • Concrete drop structure at culvert inlet

Pre-Project Barrier

  • Insufficient depth, high velocities, excessive leap
  • Partial barrier to adult steelhead trout
  • Total barrier to juvenile salmonids

Hydrologic Characteristics

  • Drainage Area: 0.6 mi2 (1.6 km2)
  • 2-year Peak Flow: 60 cfs (1.7 cms)
  • Design Capacity (100-year Flow): 266 cfs (7.5 cms)
  • Headwater-to-diameter ratio at
    266 cfs (7.5 cms) = 2.5
  • Adult Steelhead Passage Design Flows:
    • Upper = 30 cfs (0.85 cms), 50% of 2-yr peak flow
    • Lower = 3 cfs (0.08 cms)
  • Juvenile Salmonid Passage Design Flows:
    • Upper = 6 cfs (0.17 cms), 10% of 2-yr peak flow
    • Lower = 1 cfs (0.03 cms)

Channel Characteristics

  • 100-year Flow: 2,100 cfs (59.47 cms)
  • 2-year Flow: 415 cfs (11.8 cms)
  • Drainage Area: 3.61 mi2 (9.3 km2)

Ecological Value
Provide access to 0.6 miles (0.9 km) of upstream spawning and rearing habitat for steelhead trout

Project Characteristics

  • Insert a 3/8 inch (0.9 cm) thick welded steel pipe, 5 ft (1.5 m) diameter and 172 ft (52.4 m) long into existing culvert
  • Weld 43 steel corner baffles into pipe insert
  • Baffles 8.3 inches (21 cm) tall at center and spaced 4 ft (1.2 m) apart
  • 3 precast concrete weirs with wooden low-flow notches below culvert outlet
  • 9 inch (23 cm) drops between concrete weirs

Challenges and Lessons Learned

  • Bedrock surrounding culvert made “jacking” a larger pipe through the fill impractical
  • Existing culvert was out-of-round so smaller culvert had to be inserted
  • Only 25 ft (7.5 m) right-of-way available below culvert outlet for grade control weirs
  • Lack of rock armoring, and weirs not sufficiently keyed into banks resulted in flanking
  • Wooden low flow notch in center of concrete weir causes plunging water to strike concrete lip at low flow.
  • Need for inspection by personnel familiar with fish passage design concepts and objectives

Project Funding
California Dept. of Transportation (Caltrans)

Completion Date
October 2003

Total Project Cost
Costruction: $140,000

 


Project Description

The existing 5.5 ft (1.7 m) diameter corrugated steel pipe (CSP) was deteriorated and identified as a depth barrier at low flow and a velocity barrier at high flow for adult and juvenile steelhead. The culvert required rehabilitation due to its deteriorated conditions. Retrofitting involved inserting a 5 ft (1.5 m) diameter, 172 ft (52.4 m) long, welded steel pipe (WSP) into the existing culvert at a 2.4% slope. This design was selected after removing the fill to replace the culvert was deemed too costly.

Baffles were designed to satisfy, as best as possible, State and Federal velocity and depth criteria for fish passage while avoiding excessive turbulence. Hydraulics of corner baffles at fish passage flows were modeled using empirical equations developed by Rajaratnam and Katopodis (1990)1 and provided in WDFW (2003)2. The energy dissipation factor (EDF) was calculated as a measure of turbulence.

Modeled hydraulic conditions at fish passage design flows for John Hatt Creek

  Species/Lifestage: Juvenile Salmonids Passage Flows          Adult Steelhead Passage Flows
  Fish Passage Flow: Lower
 Upper Lower Upper
  Flow: 1 cfs
(0.03 cms)
 6 cfs
(0.17 cms)
 3 cfs
(0.08 cms)
 30 cfs
(0.85 cms)
  Water Depth: 0.6 ft
(18 cm)		 1.1 ft
(34 cm)		 0.8 ft
(24 cm)		 2.0 ft
(61 cm)
  Ave. Water Velocity: 0.9 ft/s
(0.3 m/s)		 1.9 ft/s
(0.6 m/s)		 1.4 ft/s
(0.4 m/s)		 4.1 ft/s
(1.2 m/s)
  Turbulence (EDF): 1.5 lb-ft/s/ft3
(71 W/m3)
 3.0 lb-ft/s/ft3
(143 W/m3)		 2.2 lb-ft/s/ft3
(108 W/m3)		 6.0 lb-ft/s/ft3
(287 W/m3)

A total of 43 corner baffles were welded into the pipe prior to insertion. Baffles constructed of 3/8 inch (0.9 cm) thick steel and spaced 4 ft (1.2 m) apart. The 9 inch (23 cm) tall baffles were rotated 15 degrees from horizontal, resulting in the low and high sides of the baffle located 4.3 and 15.2 inches (11 and 39 cm) above the invert, respectively. The gap between the existing and new pipes was filled with concrete slurry to prevent seepage.

The existing culvert outlet was perched nearly 1.5 feet (0.5 m) above the downstream water surface and the channel below the culvert was steep. To improve fish passage conditions at the outlet, three precast concrete weirs were installed within the 25 ft (7.5 m) right-of-way below the outlet. The concrete weirs were spaced 8 ft (2.5 m) apart with 9 inch (23 cm) drops. The weirs were keyed into the bank approximately 2 feet (0.6 m). Although facing class rock was to be placed on both banks between the weirs for scour protection, the contractor only placed rock on the left bank

 

Post Project Observations and Lessons Learned

The baffles appear to be effective at reducing water velocities and increasing water depth within the pipe. The weir crest elevations below the outlet were placed within design tolerances.

Rock was only placed on the left bank below the outlet which allowed for rapid bank erosion, resulting in flanking of the weirs. The bank was rocked later to prevent further erosion. Placing rock along both banks, as designed, and keying the weirs further into the banks may have prevented flanking.

A design problem with the wooden low-low notch was also discovered. The wood is not set flush with the downstream edge of the weir. Instead of plunging directily into the downstream pool at low flows, the water strikes the lip of the concrete weir. Installing a steel low-flow notch flush with the downstream edge of the concrete weir would create the desired plunging conditions at low-flow.

A steep slab of existing concrete at the culvert inlet was to be removed as part of the project. However, it was left in place. Using inspectors familiar with the project’s fish passage objectives may have avoided some of these problems.

 

References
1 Rajaratnam, N. and C. Katopodis. 1990. Hydraulics of culvert fishway III: weir baffle culvert fishways. Canadian Journal of Civil Engineering. Vol. 17:4:558-568.

2 Washington Dept. of Fish and Wildlife. 2003. Design of Road Culverts for Fish Passage.

Published 06/08/2006