Community-Based Strategies to Reduce Flood Damage
Community based strategies to reduce flood damage
Community-based strategies are not exclusively infrastructure—they include recommendations for economic development and land use combined with new safe structures programs; improving and expanding emergency preparedness and routing; and recommendations for the long-term resiliency of Chehalis Basin communities. Elements can work together to maximize flood reduction, while encompassing the shared values and guiding principles the community has agreed on.
Chehalis Basin Focus Area
Option 1
CORRIDOR FLOODPLAIN MANAGEMENT
Option 1 includes the following components:
Implement a voluntary “Safe Structures” program to protect, raise, or relocate valuable structures.
Floodplain restoration throughout the Chehalis Basin to reduce flood damage for the smaller, but more frequent flood events with small interventions such as berms, logjams, and other projects to increase the capacity of the floodplain to store water during smaller events; removes human caused barriers such as undersized culverts; and reconnects off channel floodplain and side channels. This concept incorporates the Aquatic Species Restoration Plan goals and acreage assumptions for floodplain restoration (approximately 5,000 acres of actively restored floodplain).
A black-and-white aerial photograph of the Chehalis Basin southwest of Chehalis, illustrating Option 1: Safe Structures and Floodplain Management. The image includes a graphical overlay indicating the 2080 Late Century Flood Boundary.
Specific callouts on the map describe the following key elements: 1. Maximize floodplain restoration, where feasible, that also allows existing agriculture to operate; 2. Increase access to the river using floodable parks, trails, and other open space; 3. Improve riparian areas along rivers and streams.
Option 1 provides an illustrated map showing potential restoration areas along the Chehalis and Skookumchuck rivers near Interstate 5. The map identifies Fords Prairie, Centralia, and Providence Centralia Hospital and indicates existing levees surrounding Chehalis-Centralia Airport to the south.
Potential Restoration and Recreation Opportunities
Image showing existing floodplain
Image showing floodplain after restoration is complete
Image showing floodplain restoration during flood event
Option 2
IMPROVE CHEHALIS RIVER WATERFLOW
Option 2 includes the following components:
Construct a new approximately 700-foot-wide diversion west of the Mellen Street Bridge to reduce peak flood elevations by providing another path for flood waters. The existing Mellen Street Bridge would be removed and relocated to the south. A significant amount of soil immediately upstream and for about 3,000 feet downstream of the Mellen Street Bridge would also be removed to increase conveyance opportunities for floodwater to move through this constricted area.
Implements Option 1, including the “Safe Structures” program to address residential and commercial properties inundated by flooding.
Option 2 provides an illustrated map showing potential restoration areas along the Chehalis and Skookumchuck rivers near Interstate 5. The map identifies Fords Prairie, Centralia, and Providence Centralia Hospital, and indicates existing levees surrounding Chehalis-Centralia Airport to the south.
Option 2 identifies the location of potential conveyance improvements at the major bend in the Chehalis River west of Interstate 5 and south of Fort Borst Park. It also shows the location of a potential diversion west of the Mellen Street bridge and running northwest across Providence Centralia Hospital land to rejoin the Chehalis River south of Fords Prairie.
Proposed Inlet to Diversion with Relocated Mellen Street Bridge
Image showing existing diversion – looking north toward the Hospital
Image showing the proposed diversion with new Mellen Street Bridge, open space and recreation amenities
Image showing proposed diversion during a flood
Proposed Diversion Outlet
Option 3
New and Expanded Levees
Option 3 includes the floodplain restoration and Safe Structures components of Option 1. This option would also include new floodwalls and levees, or raising existing levees, along the north side of the Chehalis River from north of Fort Borst Park downstream to Galvin Road, along both sides of the Skookumchuck River, along the east side of I-5, on the north bank of Salzer Creek, around the airport, and on the north bank of the Newaukum River near the Chehalis. Option 3 would also include daylighting (e.g., resurfacing China Creek where is is buried) and expanding flood capacity of China Creek.
A black-and-white aerial photograph of the Chehalis Basin southwest of Chehalis, illustrating Option 3: New and Expanded Levees. The image includes a graphical overlay indicating the 2080 Late Century Flood Boundary. Yellow lines indicate the location of potential levees between Interstate 5 and Chehalis, surrounding the western portion of the airport, and south of Centralia.
Specific callouts on the map describe the following elements: 1) Maximize floodplain restoration, where feasible, that also allows existing agriculture to operate; 2) Levees to protect Chehalis-Centralia Airport; 3) Floodwalls and flood gates along the Chehalis; 4) Levees to protect existing development.
Option 3 provides an illustrated map showing potential restoration areas along the Chehalis and Skookumchuck rivers near Interstate 5. The map identifies Fords Prairie, Centralia, and Providence Centralia Hospital, and indicates existing levees in northwest Centralia, south Centralia, and surrounding Chehalis-Centralia Airport to the south.
Option 3 also identifies the location of potential levees along the Skookumchuck River north and west of Centralia, along the Chehalis River south of Fords Prairie, and along China Creek, running south alongside Interstate 5 and turning back to the northeast at Solzer Creek. A potential levee is indicated along Interstate 5 east of Chehalis-Centralia Airport. The map also identifies the location of daylighting China Creek in east Centralia.
China Creek Daylighting
Image showing the existing China Creek
Image showing China Creek with adjacent new development
Image showing China Creek daylighting during a flood
Option 4
All Interventions
Option 4 includes all potential interventions and safe structure programs described in the other options, including:
- Safe Structures and floodplain restoration
- Waterflow diversion and improved conveyance
- New and expanded levees
A black-and-white aerial photograph of the Chehalis Basin southwest of Chehalis, illustrating Option 4: All Interventions. The image includes a graphical overlay indicating the 2080 Late Century Flood Boundary. Yellow lines indicate the location of potential levees between Interstate 5 and Chehalis, surrounding the western portion of the airport, and south of Centralia.
Specific callouts on the map describe the following elements: 1) Focus on areas where there is a basin-wide benefit; 2) New or expanded floodwalls and floodgates; 3) Levees to protect existing development.
Option 4 provides an illustrated map showing potential restoration areas along the Chehalis and Skookumchuck rivers near Interstate 5. The map identifies Fords Prairie, Centralia, and Providence Centralia Hospital, and indicates existing levees in northwest Centralia, south Centralia, and surrounding Chehalis-Centralia Airport to the south.
Option 4 identifies the location of potential conveyance improvements at the major bend in the Chehalis River west of Interstate 5 and south of Fort Borst Park. It also shows the location of a potential diversion west of the Mellen Street bridge and running northwest across Providence Centralia Hospital land to rejoin the Chehalis River south of Fords Prairie.
Option 4 also identifies the location of potential levees along the Skookumchuck River north and west of Centralia, along the Chehalis River south of Fords Prairie, and along China Creek, running south alongside Interstate 5 and turning back to the northeast at Solzer Creek. A potential levee is indicated along Interstate 5 east of Chehalis-Centralia Airport. The map also identifies the location of daylighting China Creek in east Centralia.