**4. Results**

#### **4.1 Groundwater fluctuations**

Depth to groundwater varied seasonally and as a result of floods, from 0 m during floods to greater than 2 m during extended dry periods in late summer and fall. **Figure 7** shows variation in water level along a central transect of monitoring wells (**Figure 1**) at representative times during the study. Three surveys are illustrated. The May 27, 2022 survey occurred during a wet period, concurrent with a minor stormflow event (peak discharge 29 m3 s −1) on Mad River. The water table is fairly flat at an elevation of 272.3 m (**Figure 7**). The Jun 28, 2022 survey occurred 15 days after a significant flood event but with trace rainfall since then. Groundwater lies below the central water hazard (**Figure 7**) and is falling. The Jul 13, 2022 survey occurred 7 days after a stormflow event (peak discharge 131 m3 s −1) on Mad River sufficient to flood lower elevations of the former course. Surface water in the central water hazard is still elevated as it is the pond along the west side of the course (at 0 m on the transect) with standing water along the western side of the transect. Groundwater elevations on either side of the central hazard are lower (**Figure 7**).

The groundwater response to two flood events, shown as a range of elevations, is also shown in the cross section in **Figure 7** for the monitoring well along the eastern edge of the transect. The respective groundwater hydrographs for stormflow events

#### **Figure 7.**

*(a) Surface water and groundwater variation for selected dates along the central transect of monitoring wells shown in* **Figure 1***. Depending on the magnitude of flooding, stormflow moves overland or through a tile connecting ponds on the western edge of the former course to the central water hazard. (b) Groundwater hydrographs for two floods, June 2022 (day one is 06-03-2022) and March 2023 (day 1 is 02-22-2023) from a monitoring well equipped with a groundwater level logger east of the central water hazard (***Figure 1***).*

*Assessing the Potential Flood Mitigation Services of a Former Golf Course with a Focus on Flood… DOI: http://dx.doi.org/10.5772/intechopen.113107*

on Mad River are also shown (**Figure 7**). The base groundwater elevations prior to the flood events were similar (272. 1 m). The Jun 13, 2022, stormflow event, which peaked on Mad River at 118 m3 s −1, is associated with a peak groundwater elevation of 272.9 m (**Figure 7**). The Mar 3, 2023, stormflow event, which peaked on Mad River at 173 m3 s −1, is associated with a peak groundwater elevation of 273.6 m. High-water marks for this event surveyed on the course ranged from 273.33 m to 273.49 m; the average high-water mark, 273.42 m, is shown on the transect (**Figure 7**). The entire transect was flooded during this event. It is important to note that the average highwater mark is approximately 15 cm below the maximum peak recorded by the water level logger (**Figure 7**).

#### **4.2 Flood storage on the former course**

From November 2018 to June 2019, 20 streamflow events occurred on Mad River upstream of the former course with peak discharges in excess of 50 m3 s −1, the approximate flow magnitude necessary for Mad River to backflow through the culverts connecting Mad River to the former course. Seven events, two of which exceeded floods with a return period of more than 5 years, were selected for the study of flood storage potential. Seven stormflow events on Mad River (circled, **Figure 8**) were selected for the study of flood storage potential on the former course. Peak discharge and total stormflow discharge for these events are summarized in **Table 1**. The total stormflow of these events accounts for 1845–13,219 K m3 (**Table 1**). Of that, it is estimated that 37–103 K m3 , or 0.4–2.1 percent of total stormflow, was stored on the former course

#### **Figure 8.**

*From November 2018 to June 2019, 20 stormflow events occurred on Mad River at St. Paris pike at Eagle City, OH stream gage (USGS gage 03267900) with peak discharges in excess of 50 m3 s −1, the approximate flow magnitude necessary for the Mad River to flood onto the former course. Flood storage was estimated for the seven events circled events.*


**Table 1.**

*Flood storage on the former Snyder Park golf course for seven flood events between November 2018 and July 2019.*

based on modeling of culvert flow (**Table 1**). The volume of storage tends to increase with the peak discharge. GIS estimates based on the difference between the elevation of the course and a flood surface representing the elevation of the flood are similar: 29–103 K m3 , or 0.3–1.6 percent of total stormflow (**Table 1**). To put this in a different perspective, the stormflow volumes reported would amount to the equivalent of storing between 5 and 8 minutes of peak streamflow discharge for the events studied.

### **5. Discussion**

With golf course closures exceeding openings in the recent past and their location and extent in predominantly urban and peripheral-urban areas, evaluating the potential reuse of golf courses for water regulation or other ecosystem services is critical. Water regulation services are considered from two perspectives, flood prevention and flood mitigation [6]. The factors most often associated with flood prevention, increased biomass, proportion of permeable surface area, infiltration capacity, and soil quality [6], also characterize golf courses. Former courses in upland urban areas are particularly well-suited to serve this function. However, it is not unusual for golf courses to be developed on "unbuildable" land, even land that is or was formerly floodplain (e.g., see the discussion thread in [9], a site dedicated to golf course architecture). Reconnecting streams to former floodplains are widely recognized as a sustainable means of flood mitigation with the added benefits of increasing floodplain goods and services and resiliency to climate change impacts [10]. The former Snyder Park Golf Course, situated on a former floodplain at the confluence of two streams, was reconnected to Mad River utilizing the existing

*Assessing the Potential Flood Mitigation Services of a Former Golf Course with a Focus on Flood… DOI: http://dx.doi.org/10.5772/intechopen.113107*

side-by-side culverts that had historically drained excessive standing water from the operating golf course.

Flood storage was estimated by two different methods with remarkably similar results (**Table 1**). During stormflow events of sufficient stage-discharge, stormflow stored on the course amounts to as much as 2.1 percent of the total stormflow volume on Mad River (**Table 1**). Results from either method of estimation are conservative as both methods rely on the stage elevation of water on the former course and do not account for infiltration as the flood wave inundates the course (i.e., the stage elevation of water does not include these concurrent losses) as it will be discussed later. There is also loss through the culverts as the flood elevation exceeds the stage elevation of Mad River as the flooding wanes. The largest stormflow event for which flood storage was estimated occurred on May 2019, amounting to 103, 455 cu m of flood storage (**Table 1**). With a high-water mark of 273.7 m, the May 2019 flood inundated more than 39.6 acres of the former course, about 91 percent of that part of the course that is not mowed or in gardens. The maximum flood storage, without impacting current maintained areas, with a high-water mark of 274.0 m, would amount to 162, 437 cu m of stormwater. The former course could receive additional stormflow, but it is ultimately limited by the volume of water able to move through the culverts.

Flood storage is likely underestimated as noted previously. Water-level data from the monitoring wells indicate that groundwater and surface water are hydraulically connected during flooding events, with surface flooding causing rapid changes in groundwater levels. By implication, the former course offers both surface and subsurface flood storage, the latter not included in the flood storage estimations. Groundwater levels rise in wells nearest Buck Creek and Mad River even during stormflow events that do not exceed the threshold necessary for surface flooding of the course, similar to bank storage [11] with some of the same benefits for flood mitigation. The two groundwater hydrographs in **Figure 7** illustrate this for events that flooded the former course. Elevation of the flood surface during June 2022 was sufficient to push water, through the tile drain, to the central water hazard. Seepage into the banks of the water hazard produced a 0.78-m rise in groundwater elevation in a monitoring well approximately 16 m further east of the central water hazard. For the May 2023 flood event, the central water hazard and well location were both inundated (**Figure 7**). The monitoring well was submerged by approximately 0.5 m of water. Though it is not possible to know whether the subsurface at the location of the monitoring well was recharged by lateral flow from the central water hazard or vertically from rapid surface flooding, it is clear that flood storage at this point on the course included approximately 1.1 m of groundwater storage and 0.5 m of surface water storage (**Figure 7**). The hydraulic connection between surface water and groundwater on the former course is facilitated by the sand and gravel outwash deposit which underlies the entire course. Diminishing groundwater levels in the days and weeks following stormflow events and flooding suggest that groundwater beneath the former course is gradually supplying baseflow on Buck Creek and Mad River.

Flood storage on the former course is fairly frequent. Streamflow discharge in excess of the 50 m3 s −1 needed to overflow onto the course occurs with an annual exceedance probability of less than 50 percent and an average recurrence interval of less than 2 years [12]. Ecosystem services directly or indirectly related to flooding and flood storage are also potentially (and frequently) provided by the former golf course. Several ecosystem services were observed or inferred, but not measured, here. Given the nature of stormflow in Midwestern U.S. watersheds dominated by agricultural

uses (e.g., excessive sediment and nutrient loads), the former course provides supporting services like soil formation and nutrient cycling. Sandy deposits nearest the culverts and cores from ponds nearer the culverts showing fine sand, silt, and clay, and fine silt recently deposited on reduced muck and sand and gravel, and a thin layer of clay coating vegetation on flooded surfaces all indicate sediment accumulation. Carbon storage on the reconnected floodplain provides climate regulation, especially as the formerly hydric soils are more routinely saturated due to flooding. The increased residence time associated with flooding and the infiltration of stormflow would result in increased water quality, which is returned to Buck Creek and Mad River as baseflow. A conceptual plan for the park district managing restoration of the former course is based on these services in its early stages. It includes excavating a waterway near the culverts to promote flow onto the course, removing barriers between, and enlarging, ponds on the western edge to increase storage, and lowering the topography in and adjacent to the central water hazard to restore it as a wetland. In addition to walking trails and wildlife observation decks, different land covers include woodland, prairie, wet meadow, and pond.

## **6. Conclusions**

Golf course closures exceed new course openings in the U.S. and many comprise large tracts of green space in urban areas without clear plans for future use. Course closures in urban areas and the periphery provide an opportunity for maximizing ecosystem services beyond typical cultural services (i.e., trail walking, nature viewing, and outdoor education), increasing community resilience. The focus of this study is a closed golf course on a former floodplain at the confluence of two streams, Buck Creek and Mad River, the latter of which is connected to the course through two culverts that historically drained excess water from the course. This study reports the results of two methods for estimating flood storage, a culvert flow model based on head differences between the stream and ponding on the former course and a GIS flood volume model based on high watermarks. Streamflow on Mad River in excess of 50 m3 s −1, a relatively minor flood with an exceedance probability of greater than 50 percent, is sufficient to flow onto the former course. For the stormflow events modeled, the former course stores 0.3–2.1 percent of total stormflow with good agreement between the two methods, but they likely underestimate actual storage. Concurrent with surface flooding, stormflow is being infiltrated causing groundwater levels to rise in flooded areas as well as in areas without surface flooding.

### **Acknowledgements**

Students in my watershed hydrology course helped to install monitoring wells during preliminary investigations. Andrew Francis and Christian Smith maintained, collected, and analyzed water-level data from them as well as helped with water level surveys.

*Assessing the Potential Flood Mitigation Services of a Former Golf Course with a Focus on Flood… DOI: http://dx.doi.org/10.5772/intechopen.113107*
