The Field

The Oktibbeha County Heritage Museum was founded in 1976 in Starkville, Mississippi, just a half-mile from both the historic downtown area and Mississippi State University, to preserve, publicize, and educate the public about the rich history of the region. The building itself is housed in a renovated railroad depot first built in 1874, but renovations initiated in 2009 by the Departments of Landscape Architecture and Architecture at Mississippi State University sought to make the museum a demonstration case to the alternative water management and habitat creation practices being implemented around the country to incorporate green infrastructure into the urban setting.

When the “Rain Garden” project was finished in spring 2013, a green roof pavilion, cistern, and infiltration areas had been installed on the 0.5-acre site to retain and clean rainwater. The purpose of this report is to document the ways in which the Rain Garden project has benefited the Oktibbeha Heritage Museum and the surrounding areas, a measurement termed Landscape Performance. Four distinct benefits have been explored: environmental, social, economic, and educational. These benefits were compared before and after the Rain Garden installation.

The Oktibbeha Heritage Museum is centrally located around apartment housing, shopping centers, and the largest open green space in town, the city cemetery. One block over lies the western edge of the internationally-recognized, new-urbanist, mixed-use Cotton District. The museum building itself is a 5,000sf structure, whereas the exterior, prior to the design installation, was primarily used as a concrete parking lot with minimal foundation plantings and no exterior amenities for public use.

After the Rain Garden project installation, a green roof, flow-through planter, and vegetated retention cell/infiltration basin was constructed to capture and clean site and roof rainwater in a visually-stimulating process that engages the visitor and supports a vibrant ecosystem of native flora and fauna (Figure 1). Further additions included a 1,000g cistern to meet irrigation needs during occasionally-hot Mississippi summers and educational plaques displaying water management concepts for public education. Hard elements comprised of wood, industrial metal, and the creative use of railroad ties reflect both the architecture of the building and connect the place to its historical roots. Social gathering spaces allow for well-lit nighttime and daytime activities under the green roof pavilion as well as outdoor movie nights under the stars utilizing the green space and seating areas.

Landscape Performance

The Curve Number (CN) approach was applied to pre- and post-development site conditions to determine stormwater runoff differences after accounting for land-use type and soil infiltration rates (TR-55, USDA-NRCS 1986). The following formula was used to determine a weighted CN value for the total site area:

∑(Area1 * CN1) + (Area2 * CN2) + (Area3 * CN3) + … / Total Site Area

where Total Site Area was 0.56 acres (or 24,393 sf) and CN values ranged from 0-98.

Mean CN values weighted by total area for pre- and post-development conditions were 87.7 and 62.3, respectively. These findings indicate a pre-development mean land-use type similar to the hydrologic condition of a compacted dirt road (CN=89, TR-55 USDA-NRCS 1986). By comparison, the post-development mean land-use type is brought to the hydrologic condition of a densely-vegetated, well-drained, upland soil (CN=63, TR-55 USDA-NRCS 1986).

Using the National Tree Benefit Calculator (a website that determines pounds per tree based on diameter breast height (DBH) and genus/species), we found no loss in carbon (C) storage between the loss of pre-development trees (801 lbs.) and the planting of post-development trees (815 lbs.). Furthermore we expect the post-development trees to grow to hold 2,335 lbs. in the future (when the trees double in DBH), representing a roughly 300% C storage increase. We also found an 18% increase (sf) in shade cast on-site in post-development conditions, but, as the young trees continue to mature over time, this shade model will change to reflect tree growth. A plant species comparison found much higher diversity following the design installation (82 species) compared to before (6 species). The new plantings are completely comprised of native species that are important food and nesting areas for bird, butterflies, and other pollinators.

In terms of economic benefit, 2015 membership revenue is 20% higher than in 2012 and generous contributions have increased from $100 to $2,812 in the same time period. Grant awards from the city of Starkville and the county rose 43% and 25%, respectively, between 2009 and 2015. Net income has risen from $1,569 in 2012 to $10,999 in 2015, about a 7x increase.

Social programming at the museum has benefited from the Rain Garden project, such that annual fundraisers, like the Denims & Diamonds event, currently bring in more guests than back in 2012. New programs became available such as nighttime dance performances (Beaux Arts Ball) and outdoor movie nights, especially with the addition of new ADA-accessible facilities.

Educational benefits continue to be enjoyed by Mississippi State University Landscape Architecture, Architecture, and Home Economics students more so than primary and secondary schools in the city. A total of 101 undergraduate students and 13 graduate students from 7 different departments on campus were involved in the project construction, bringing educational opportunities to students from a variety of disciplines. The project has won Mississippi ASLA awards as well as an ASLA National Award of Excellence in 2013 for Student Collaboration in Service Learning.

Conclusion

In summary, this landscape performance study documents benefits of the Rain Garden project in a variety of different areas because it is important to apply quantitative analyses to landscape architecture design goals in order to further validate their worth. This study found positive effects in environmental, economic, social, and educational areas after just a 3-year period, and these benefits will continue to be measured to further track the investment returns of the Rain Garden project design.

Highlights

• A landscape performance assessment was made at the Oktibbeha Heritage Museum in Starkville, Mississippi to determine if the “Rain Garden” project (completed in 2013) has had any effects on the environmental, economic, social, and educational aspects of the site.
• Water management benefits and economic return-on-investment (ROI) were the most significant improvements seen over the 3-year analysis period.
• Post-development quantitative analysis can attach monetary, hydrologic, social, and educational value to landscape design features to further demonstrate the broad, positive impacts of an integrated site design.

by Michael Keating, Student ASLA, and Ying Qin, 2nd-year graduate students at Mississippi State University. They were advised on this project by Dr. Chuo Li.

References

“National Tree Benefit Calculator.” National Tree Benefit Calculator. Casey Trees, Davey Tree Expert Co., n.d. Web. 29 Jan. 2016.

USDA – NRCS. Urban Hydrology for Small Watersheds: TR-55. Rep. Washington, D.C.: USDA, 1986. Print.

Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. 29 Jan. 2016.

“Oktibbeha County Heritage Museum in Starkville, MS.” Heritage Museum Events. Oktibbeha County Heritage Museum, 2016. Web. 29 Jan. 2016.