Location: Pierce County, Washington

Highlighted Element: 422.g. Low Density Zoning (LZ) & 432.a. Development Limitations (DL)

Point of Contact: Dennis Dixon, CFM, Surface Water Management Engineer, Pierce County, WA

Pierce County is Washington the state's second most populous county and home to 795,225 residents (US Census Bureau, 2010; Pierce County, 2016). Covering approximately 1,793 mi2, this vast county stretches from Puget Sound to Mount Rainier and is roughly the size of Delaware (Pierce County, 2016). Pierce County has a long history of flooding. Since 1990, nine federal disasters have been declared as a result of flooding ("Flood District FAQs," no date). The county has 11 "significant floodplains" that range from urban and highly developed to rural and sparsely populated ("Flood District FAQs," no date). According to the county flood control district, the predicted losses from a severe flood event in Pierce County are in excess of $725 million ("Flood District FAQs," no date). However, the adverse impacts of a severe flood are not just financial. An estimated 11,800 individuals have jobs or businesses within the 100-year floodplain that could be impacted by a significant flood ("Flood District FAQs," no date). These broader effects of flooding impact the livelihoods of residents and businesses that rely on them in order to have their basic needs fulfilled. How does a county that is the size of a small state and has topography that is so variable that it stretches from the peak of Mount Rainier to sea level, ensure that it will remain resilient to flooding? In this case, policy has been a critical tool for shaping and resisting the pressure to develop lands in the regulatory floodplain.

Low density zoning allows farms to be built on high ground. Image courtesy of Helmut Schmidt, Pierce County Public Works - Surface Water Management.

Beyond Tacoma and its suburbs, Pierce County remains fairly rural. Sprawl has been limited in large part due to a relatively new planning tool that is used by communities—the urban growth boundary. Implementation of this urban growth boundary in Pierce County was required under the 1990 Washington Growth Management Act, which mandated Washington State's most populous and rapidly growing cities and counties to engage in a coordinated comprehensive planning processes, work together to establish urban growth areas beyond which high density development cannot occur, and create regulations that protect forests, agriculture, and other critical resources areas (RCW 36.70A.060; RCW 36.70A.045; "Comprehensive Planning/Growth Management," no date). The expansion of these Urban Growth Areas are now explicitly prohibited in the 100-year floodplain, which prevents rapidly developing areas from encroaching on intact floodplains (Pierce County, 2016). In accordance with the county's comprehensive plan and requirements of the Growth Management Act, the county and its major cities have developed limits beyond which the character of the land is intended to remain rural in nature with single-dwelling lot sizes generally being 5 acres or more (RCW 36.70A.060; Pierce County, 2016). As a result, a majority of the county remains rural, with areas being zoned at very low densities. In doing this, Pierce County has managed to achieve a delicate balance between allowing some development to occur, while also leaving ample amounts of areas open to function as they would in nature.

Although maintaining large lot sizes helps to minimize the adverse impacts associated with development in the floodplain, it does not prevent those structures from incurring damage when water levels rise. In order to ensure new development and substantial improvements to existing structures are resilient to future flooding, Pierce County has put into place several regulations that manage where and how development occurs in floodplain areas. For example, all new development is strictly prohibited in the floodway. Important to note in this case is that Pierce County's regulatory floodway extends beyond the standard FEMA floodway due to the way the county defines it. Essentially all areas where water is 3 feet or more deep and/or flowing at a velocity of 3 feet/second or more, or a combination of the two (e.g. a flood depth of 1.5 feet flowing at a rate of 2 feet/second) are mapped as floodway. As a result, the county's regulatory floodway is very large.

Farmlands are flooded while most structures are protected. Image courtesy of Dennis Dixon, CFM, Pierce County Public Works - Surface Water Management.

The county's code prohibits new development in the flood fringe unless there are no feasible alternatives to building outside of the Special Flood Hazard Area. When new structures are permitted to be constructed in the flood fringe, property owners must meet standards such as including safe egress during a flood in order to allow residents to safely evacuate their property, and demonstrating that any fill placed does not increase flood flow velocities, elevations or decrease the available storage (PCC 18E.70.040_C-2). As a result, a significant amount of compensatory storage is required for most development in the flood fringe. To protect life, property and the natural functions of rivers, channel migration zones are subject to the same regulations as floodways. This has effectively increased the total area of all floodways within Pierce County from approximately 5,000 acres to 10,000 acres.

Learn more about how your community can take credit for low density zoning or the implementation of sound development regulations in the floodplain. Check out the Green Guide profiles of elements 422.g. Low Density Zoning and 432.a. Development Limitations.

But the success of these regulations depends on their ability to withstand opposition from the general public, development community and local government officials who represent these constituents. In order to communicate flood risk to current residents, developers and future homeowners, the county created a publicly available GIS web-map that allows residents to overlay data layers. In doing this, anyone with a computer can readily look up whether or not their current home, planned development or other neighborhoods are subject to flooding and/or other natural hazards like erosion and landslides. They can even check if the parcel has potentially sensitive natural areas located on it like fish and wildlife habitat or wetlands. This has helped increase the transparency between the county's floodplain management staff and the general public, and empower residents and developers to make informed decision based on flood risk.

The Department of Surface Water Management, which oversees the implementation of the county's floodplain management program, has also built a strong relationship with many of the departments that benefit from decreasing flood risk and managing expectations of the public. So when there are suggestions to loosen the stringency of the floodplain management regulations, the Department of Emergency Management will step in and help defend the county's floodplain management regulations. As a result, while these regulations have been subject to criticism at times, they have endured changes in local politics.

While regulations discussed in this success story were enacted to protect life and property from flooding in Pierce County, they also have several co-benefits for the environment. By subjecting channel migration zones to the same regulatory standards as floodways, the county has effectively reduced the number of properties at risk of being damaged by a flood event on a river or stream that has historically migrated. The demand for shoreline armoring like rip rap and gabions implemented to stabilize channel banks has been reduced substantially.

Flooded Puyallup River. Red lines indicate the historic location of levees on this creek. Since then, these levees have been setback to allow the river to meander in a more natural pattern. Image courtesy of Dennis Dixon, CFM, Pierce County Public Works - Surface Water Management.

This has allowed the flow regimes of some streams in the county to return to "normal." As a result, channel banks can undercut and eventually migrate as they would have prior to human settlement. Along the way, these streams pick up sediment, rocks and logs that are eventually deposited downstream, diversifying in-stream habitat for fish and macroinvertebrates and enhancing biodiversity as a result.

Best practices shared by this community:

  1. Documenting what your community is already doing well can often times lead to CRS credit.
  2. Understand what FEMA gets out of the program and what the agency's goals are. This will help communities grasp why the CRS program rewards certain floodplain management practices over others and why it is useful.
  3. Have patience. Learning how the program works and putting into place the systems necessary to efficiently document CRS activities takes time.

For all the actions Pierce County has taken to preserve the rural character of a majority of its land; prevent future subdivision and development of land in floodway; and help ensure development in the flood fringe is resilient to future flooding, the county has been awarded a Class 2 ranking in the CRS program. Flood insurance policyholders within the county receive a 40% discount on their premiums, which equals more than $530,000 in savings for homeowners each year.