Naturalization of Fassnight Creek, An Urban Stormwater Success Story

Introduction
Our urban centers are plagued by a variety of concrete storm water conveyance structures. Originally intended for flood control, they have simply moved the flooding to downstream areas while degrading natural stream habitat. It's well documented that nature-based solutions mitigate stream habitat degradation, but can they also perform a vital flood risk reduction purpose in our urbanized neighborhoods?

General Project Information
As part of a larger master plan for the Springfield Art Museum, Fassnight Creek was restored to a naturalized channel for flood mitigation, water quality, and wildlife habitat improvement. The Springfield Art Museum is located in the heart of Springfield, just south of Missouri State University. Adjacent to the museum is the historic Phelps Grove Park which is beloved by the community for its mature trees and pedestrian trails. The museum and Phelps Grove Park are surrounded by well-established residential neighborhoods and a high-level of pedestrian activity, which made this project an impactful addition to the urban greenspaces in the area. Before the capital improvement project, Fassnight Creek was confined in a narrow concrete channel with insufficient hydraulic conveyance. The Fassnight Creek Improvements widened the channel cross section significantly and naturalized approximately 1,000 linear feet of creek channel, encompassing 1.5 acres of newly re-stablished riparian area, that serves as an urban wildlife corridor and extension of the Phelps Grove Park greenspace. The restored channel contributes to the overall quality of place and helps to further integrate Phelps Grove and the Art Museum grounds. Key components of the natural channel design include use of void-filled native rock materials to emulate the natural stream bottom of local streams and extensive native plants. Construction included excavation of approximately 16,000 CY of soils, removal of 900 feet of concrete channel lining, removal of a public street crossing, installation of over 250 linear feet of 21-inch sanitary sewer main, two new pedestrian bridges, creating a natural pool and riffle stream, mitigating culvert erosion and re-alignment and narrowing of Brookside Drive centerline to give additional area for channel improvements. Channel Naturalization Details Native plantings provide multiple benefits including creation of habitat to support pollinators, aquatic species, and other wildlife. The native landscaping included planting of over 25 native trees and over 200 native shrubs. Missouri native plantings obtained from regional sources. In addition, City urban forestry crews carefully excavated and rehabilitated a small sycamore tree known to the local residents as the 'child sycamore' and this tree was successfully re-planted in the center of the creek corridor after the grading was completed. The plantings are integral to the project's goals to improve water quality and reduce flooding through filtration and uptake of common pollutants and absorption of stormwater runoff. The project also will increase awareness and acceptance of native plants due to its visibility by local and regional Art Museum visitors. The project will also enhance the Art Museum as a local field trip destination for Science, Technology, Art & Math (STEAM) programs. The Art Museum currently partners with the non-profit Watershed Committee of the Ozarks on the Placeworks STEAM Residency that uses journaling to connect science and art and includes field trips to the Art Museum. There is also a desire for the Art Museum to serve as a monarch way station to tie in with butterfly habitat efforts at the Botanical Center on the south side of Springfield. On this project, the channel slope and shear stress exceed a fine grain channel bottom or a fully vegetated solution which is likely why a concrete liner was used in the past. Fortunately, many local streams are predominately bedrock influenced gravel bed streams. We were able to mimic the natural stream bottom utilizing void-filled rock. Void-filled rock mimics local natural stream bottom where native graded cobbles, boulders, and small aggregates are mixed form a densely packed heterogeneous mixture. For the Fassnight Creek restoration project, the concrete was removed and the rock mixture used to create a stable natural channel bottom. The engineered mixture of stones and smaller sized river gravel aggregates compacted in layers ranging from approximately 2 to 4 feet thick. Selected areas of the void-filled riprap are planted with native grass plugs to add aquatic habitat value but also reinforce overbank areas of the channel with rooted plantings. Void-filled stone structures have been placed along the channel alignment to form riffles and pools seen natural streams alignments. These pools and riffles are the foundations for aquatic habitat in the creek.

Floodplain Information
A central project objective was to reduce base flood elevation (BFE) and mitigate flood risk for the Springfield Art Museum and surrounding residential properties in this area. Based on revised, preliminary 2019 FEMA maps, portions of the Springfield Art Museum and surrounding residential properties are within the 1% and 0.2% SFHA. Flood Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) for Springfield are currently being updated to provide more accurate depiction of flood risk for the community but have not yet been formally adopted at this time. The City of Springfield's proactive approach now has the Art Museum and residential properties well positioned for the formal adoption of the revised preliminary FEMA floodplain maps. The improvements lowered the 1% BFE approximately feet. Following the Improvements to Fassnight Creek at the Springfield Art Museum, the surrounded properties finished floor elevations have a much lower flood inundation residual risk. Construction and Funding Fassnight Creek at the Springfield Art Museum was substantially completed May 31, 2022. The construction began in Spring 2021 and took slightly longer than 1 year to complete. Construction involved complicated sanitary by-pass pump around for sanitary sewer main relocations, and constant vigilance on the part of the general contractor to maintain erosion and sediment control best management practices during active construction within the creek. Following construction, the ribbon cutting grand opening occurred October 15, 2022 with the Mayor, City Administrator, three Councilmen, the Art Museum director and the Art Museum board of directors presiding. Fassnight was recently recognized as an APWA Missouri Chapter Public Works Project of the Year because it demonstrated a functional solution to flood risk reduction which can serve many other beneficial purposes for the community. The naturalized channel is the new grand entrance to the Museum, an inspirational functional piece of living art. The overall construction costs for the project were approximately $2.3 Million. The Project was partially funded by grant funding from the Missouri Department of Natural Resources, EPA Section 319 grant funding Administered by the non-profit James River Basin Partnership, and grant funding for native plantings from the Missouri Department of Conservation. The local funding share was provided by the City's ¼ cent capital improvement sales tax.