Novato Creek Bypass Study Project

About

As presented at the February 6, 2017 Advisory Board meeting, a limited evaluation of potential flood reduction benefits at Scottsdale Pond was included in the Novato Watershed Study. In November 2020, staff recommended additional analysis of Novato Creek and the flood bypass system from Arroyo Avichi near South Novato Blvd through Baccaglio Basin, Scottsdale Marsh, and Lynwood Basin. the new study would leverage the new City of Novato storm drain model and the new Countywide LiDAR surface data. Based on feedback from the advisory board and the Old Town Novato Flood Group, here are the primary objectives of the study:

  1. Summarize the list of potential projects to model
  2. Identify opportunities along Novato and lower Warner creeks and through the bypass drainage system for new flow gates, perimeter barriers, pump stations, and increased stormwater detention that would reduce flood risk in downtown Novato and Nave Gardens.
  3. This includes alternatives to existing systems (i.e. move pump station from Lynwood Basin to Scottsdale Pond). This analysis is key because of the potential costs for repairing the Lynwood Pump Station in its current location (estimated at $3M)
  4. In addition to considering alternatives to sediment removal every four years, evaluate alternative footprints and triggers for sediment removal.
  5. Evaluate potential project alternative benefits for smaller flood events (e.g. 10-year event) than the 50-year.
  6. Apples to apples comparison of project alternative benefits and costs, project ranking (aim for 1-2 criteria), and review criteria with advisory board.
  7. Comprehensively evaluate the trade-offs between projects that benefit Nave Gardens/South Novato Blvd and their impacts elsewhere.
  8. Identify how to fund projects (grants and/or if loan is feasible).
  9. Review with City any  potential storm drain improvements that may be more effective in conjunction with potential Zone 1 projects and any opportunities for flow gates in City’s road right of way.

In 2020 the District solicited Statements of Qualifications from firms interested in performing on-call work. One of many respondents included Wood Rodgers (WR), an engineering firm that has extensive experience in storm drain modeling and uses the proprietary software developed for the City of Novato’s storm drain model. Staff issued Wood Rodgers the first task request, under their on-call contract, for the ABSL Complex study scope that includes elements 2, 4, 6, and 7 above. Note that there are some unknowns identified in the WR scope that may require additional scope and budget once their initial analysis is done. To this end, the budget includes an as-needed amount of $54,425 in the event that additional work is required.

Timeline

The study is anticipated to be completed in 2023. However, model calibration will require minimum amounts of rain during winter 2022-23.

Status: Mapping and inspections of storm drains, drainage ditches and other facilities in Nave Gardens were completed in 2021. A draft scope for a hydraulic study focusing on the bypass system around this area was prepared for advisory board consideration. The estimated total cost as scoped is approximately $250,000. In December 2021 the advisory board recommended a professional services budget adjustment of up to $300,000 for this study. The first step is reviewing existing models and studies and installing water level gauges in the study area. Water level gauges were installed in fall 2022, with the rain events of winter 2022/2023 providing good data for the model development. In January 2023, the existing conditions model is being completed and an update will be provided to the Advisory Board in February 2023.

Zone

Zone 1: Novato

Agencies and partners

  • City of Novato
  • Old Town Novato Flood Group
  • County of Marin Flood Zone 1

Contact

Close window