Tributaries
Brown Township is located within the Big Darby Creek watershed, which is a portion of the Scioto River drainage basin. Big Darby's headwaters rise near East Liberty in southeast Logan County and flow about 78 miles, emptying into the Scioto near Circleville in Pickaway County. The creek and its tributaries drain an area of about 557 square miles, including portions of Logan, Union, Champaign, Clark, Madison, Franklin and Pickaway Counties.
The Township is drained by several tributaries, in particular Hamilton Ditch which services about one-third of the Township, functioning as the eventual stormwater outlet for the eastern portion of the planning area. Hamilton Ditch is tributary to Hellbranch Creek. Several other minor ditches are located in the western half of the Township, including Sherwood, Worthington-Sherwood, Leap and Burkett Ditches. All of these ditches are in the Darby Creek watershed. Map No. 5, Tributary System, depicts this information.
Floodplains
The 100-year floodplain has been mapped along Big Darby Creek, Hamilton Ditch and Clover Groff Ditch. The 100-year floodplain is far more extensive along Hamilton and Clover Groff Ditches than along the Big Darby, reflecting the nearly level topography found along the two ditches. Land use impacts, thereby, are geographically more extensive in the eastern portion of the Township.
Stormwater Drainage
Drainage is an important land use consideration, because areas that are poorly drained can result in a variety of negative impacts: wet basements, cracked foundations, flooded property and related maintenance problems. Agricultural areas are particularly impacted by poor drainage.
The nearly level topography that typifies Brown Township is a leading cause, in addition to poorly drained soils, for poor stormwater drainage because it places physical limits on natural drainage systems such as streams. Hamilton Ditch, which drains about one-third of Brown Township, has a shallow depth and gradient, is heavily silted and vegetated and is generally ineffective in removing excess stormwater.
A. OCAP/ODNR Assessment
An assessment prepared by the Ohio Capability Analysis Program (OCAP) shows about 78 percent (11,278 acres) of the Township has drainage problems; either "very poorly drained" or "somewhat poorly drained". The balance (22 percent) has "good drainage" and of that, only about 5 percent is considered "well drained" based upon this assessment. Figure 9 shows this relationship.
The Ohio Department of Natural Resources noted in its corridor study of Big Darby Creek that portions of the flat uplands, which have Crosby and Kokomo soils, are poorly drained and have a high water table, resulting in problems of ponding, basement flooding, and septic tank failure.
B. Local Studies
Drainage problems in Brown Township have been officially identified in studies dating to at least 1969, when the Franklin County Comprehensive Plan stated, "Because of the extreme flatness of the area and difficult drainage problems north of I-70 near Hilliard, it is recommended that the area (Brown Township) not be residentially, commercially, or industrially developed."
The Water-Related Facilities Plan, prepared by Burgess & Niple, Ltd., for the Mid-Ohio Regional Planning Commission in 1969, questioned the investment for physical drainage improvements in the Township, noting that "severe ponding may be expected regardless of the drainage facilities provided, with distressing consequences attendant on those who build there."
C. MORPC Study
The Brown Township Drainage And Land Use Study, prepared by MORPC in 1982 for the Township Trustees, delineated boundaries of three major drainage areas in the Township and developed specific drainage policies for each.
The following is excerpted from the study:
Area A
The western portion of the Township, Area A exhibits positive surface drainage (generally greater than two percent slope) and drains into Big Darby Creek. As a result, stormwater drainage is not a limitation for development in Area A. Outlets to Big Darby Creek are a number of parallel ditches. While the lower reaches of these ditches have good flow characteristics, the upper reaches extend into Area B where topographical conditions allow for an average slope of one-half percent or less. |  |
Area B
The central portion of the Township, Area B is subject to poor local drainage conditions due to flat topography, but eventually drains to Big Darby Creek, a suitable stormwater outlet.Area B soils are subject to severe local ponding. Site specific constraints to development result from a high water table, depressional and flat terrain, and inadequate surface or subsurface drainage outlets. The nearly flat topography serves to negate positive drainage, even with the addition of improvements to the major ditches leading to Big Darby. |
Area C
The eastern portion of the Township, Area C is subject to poor local drainage conditions due to flat topography and drains into Hellbranch Creek via Hamilton Ditch. Neither tributary effectively removes stormwater for Area C due to the existing shallow gradient (which is compounded by siltation and heavy vegetation in the tributaries). |
Area C is the most severely impacted by drainage restrictions of the three study areas in Brown Township. Area C constitutes the upper watershed for Hamilton Ditch which has an average slope of 0.11 percent between Scioto-Darby Creek Road and I-70. A "drainage sensitive area," Area C contains soils subject to seasonal ponding and extensive 100-year floodplains.
A ditch improvement project would upgrade the flow characteristics of Hamilton Ditch, thereby providing an improved outlet for subsurface tile connections. But such an improvement would not address the site and area conditions of undrained depressions and flat surface grades. As the study states, "such a project would only be effective in helping the high water table in the immediate vicinity" of Hamilton Ditch.
Sedimentation of Hamilton Ditch would continue to be a maintenance problem, because of the extremely flat ditch grade and low flow velocities. (A further restriction is the high groundwater table coupled with extreme levelness, which together restrict on-site wastewater systems for residences.)
D. Franklin Soil and Water Conservation District
The FSWCD began a stormwater management study of the Hellbranch watershed in late 1991. Those results should be reviewed in light of this Plan following the District's completion of their study.
