Surface Water Management Division

Drainage Needs Program

In December 2002, a team of Snohomish County staff and consultants completed a two-year study that inventoried existing drainage systems and evaluated stormwater drainage problems and solutions in the County's rapidly growing urban growth areas (UGAs). This ambitious project, called the Drainage Needs Report Project, involved the assessment of drainage needs throughout the County's unincorporated UGAs. The results provide a wealth of information and new tools that the County, local cities, developers, and citizens alike can use to make decisions on drainage related issues. These tools are designed to answer questions not only today but also in the future, as conditions change.

Products of the Drainage Needs Report Project

• The inventory of 73 square miles of existing drainage systems - mapped for the first time (includes 15 square miles of inventory conducted prior to the DNR project and 58 square miles of inventory conducted during the DNR project).
• The identification of over 1,000 existing and future surface water problems.
• A list of 378 priority projects with conceptual designs.
• The development of hydrologic and hydraulic models for a number of the major conveyance systems.
• Eleven individual Drainage Needs Reports for individual study areas.
• A Summary Report for the entire DNR Project.
  

The benefits of the DNR Project

• The County can better maintain and repair drainage systems it owns or manages.
• Residents can have a better understanding of drainage systems in their neighborhoods.
• The County and other local governments can prioritize drainage system investments and better coordinate with other regional projects.
  Developers have access to new information and hydrologic/hydraulic models for conducting downstream analyses as part of the permitting process.
• Emergency responses to contaminant spills can trace downstream drainage paths more quickly.
• Aquatic habitat and water quality can be better protected.
  

Additional information

DNR Summary Report & Individual Study Area Reports

2005 Status Report for DNR/MDP Flooding Projects

DNR/MDP Drainage Projects fundedfor construction in 2006 (14.5 KB PDF download)

Map of the eleven study areas (146 KB PDF download)

Drainage Inventory Maps

DNR Summary Brochure (4.96 Mb PDF download)

December 2002 Press release for DNR Project (PDF download)

Questions about the Drainage Needs Report Project? Need to obtain hydrologic and/or hydraulic models created for the project?

Contact

Gregg Farris, DNR Technical Manager, 425-388-6454

Many of the documents are in pdf format. To read these files you'll need to have Adobe Acrobat Reader installed on your computer.