Comparison of stormwater management in a karst terrane in Springfield, Missouri — case histories

Abstract

Control of stormwater in sinkhole areas of Springfield, MO has involved the utilization of several standard approaches: concrete-lined channels draining into sinkholes; installation of drainage pipes into the sinkhole “eyes” (swallow holes); filling of sinkholes; elaborate drains or pumps to remove stormwater from one sinkhole and discharging into another drainage basin or sinkhole; and enlargement of swallow holes by excavation to increase drainage capacity. Past planning considerations and standard engineering approaches have resulted in flooding of sinkholes and drainage areas, including residential, industrial and commercial developments. Having recognized the inadequacy of existing designs to control flooding and the need to accommodate increased runoff from future development, the City of Springfield adopted an ordinance (effective 19 June 1989 and modified in 1990 and 1993) in response to public pressure and concerns over flooding in sinkholes and sinkhole drainage areas. Three sites were analyzed to examine the effectiveness of contrasting design approaches to stormwater management. These sites differ in vegetation, on-site/off-site considerations, and types of development proposed. All three sites are located within the East Cherry Street Sinkhole Area. The first site, a wooded tract with unmodified sinkholes was cleared and developed for residential use. Discharge of stormwater was directed into sinkholes, and erosion control consisted of hydro-mulching and sedimentation fences in sinkhole areas. East of this location are two parcels which differ in removal of vegetation and off-site drainage relationships. Stormwater design in these sites was adapted for modifications made to sinkholes during railroad and highway construction several decades earlier. Sediment fencing, hydro-mulching and detention berms augment infiltration, restrict erosion, retard discharge to sinkholes, and incorporate off-site considerations. Ongoing observations of stormwater behavior indicate problems of flooding and sediment control at the western site but minimal disruptions of existing drainage patterns at the eastern sites. Design calculation for the western site show adequate volume retention in sinkholes, but different design approaches were implemented to “soften” the impact of stormwater discharging into these sinkholes, allowing for minimal disruptions in the natural drainage network. The lack of recognition of sinkholes as integral parts of dynamic hydrologic systems may result in problems with on-site/off-site drainage. Standard engineering designs for stormwater detention are not appropriate for the hydraulic characteristics of the shallow karst drainage network. While runoff estimations are conservative, the design calculations fall short of adequately addressing actual stormwater runoff characteristics.