Watershed Description

The Thorpe Creek-Geist Reservoir Watershed is the largest of the 9 watershed (22,170 acres) referenced in this Master Plan. It drains land from Madison County, City of Noblesville, Town of Fishers, and City of Indianapolis into Fall Creek and Geist Reservoir. About 40% of this watershed is within the Town of Fishers planning area, of which only 42% is within the Fishers Town incorporated areas. The major waterways in this planning area include Fall Creek and unregulated portions of Thorpe Creek, Bee Camp, and Thor Run as well as 9 regulated drains (Thorpe Creek, Thor Run, Canal Place, Bee Camp Creek, Beaver & Brooks, Sail Place, AJ Meyers, Martha Ford, and John Underwood).

Geist Reservoir is located in the lower portion of this watershed. As the second largest lake in Indiana, it provides a valuable drinking water source, flood control for Fall Creek, and recreation opportunities for central Indiana. Although built in 1943, residential development around the reservoir did not occur until after the 1970s when a plan to triple its size fell through. Development in other parts of the Thorpe Creek-Geist Reservoir Watershed has been more recent. The land use today, is predominantly single family residential (44%) developments or undeveloped as agricultural land (26%).

Existing Conditions and Concerns

Existing condition and concerns were gathered using a variety of data sources. All resources are referenced in Chapter 7 of this Master Plan.  Supporting documentation on water quantity data listed below can be found in Appendix 2 and water quality in Appendix 3.

• Detailed floodplain studies (Zone AE) have been completed for Thorpe Creek, Bee Camp Creek, and Fall Creek. Approximate (Zone A) delineations exist for Geist Reservoir and Thor Run.
• The approximate Zone A delineations for Thor Run and Geist Reservoir appear to have erroneously included high ground in the floodplain and not included some areas that are in the floodplain.
• A study was also done for the Hamilton County Surveyors Office along a portion of Bee Camp Creek to recommend solutions to bank erosion problems.
• There are 2 USGS stream gauges monitoring flow and stage level within the larger Fall Creek watershed. One gage is located at 71st Street in Indianapolis. Readings of 76 different parameters have been taken monthly since 1991. The other gauge is located near Fortville on Fall Creek. That gauge has been operating continuously since 1941 providing flow and stage data.
• The riparian corridor along Thorpe Creek is generally less than 50 feet wide until the confluence with an unnamed tributary at Florida Road where is become more densely wooded (150 feet) with large residential setbacks. Limited vegetation and minimal setbacks around Geist Reservoir. Bee Camp Creek is wooded however with little setbacks.
• There are 15 acres of notable palustrine forested, broad leaved deciduous temporarily flooded wetlands identified along Thorpe Creek at Atlantic Road (9 acres), north of 126th St east of N. Cyntheanne Road (3 acres), and south of 126th Street west of Atlantic Road (3 acres).
• This watershed is in the process of becoming fully urbanized. Britton Falls is a large mixed use residential and commercial development in the northeast corner of the Town of Fishers planning area. Southeast Fishers is a 500 acre residential development project southeast of Geist Reservoir.
• Imperviousness estimated to be 30% which is typically indicative of moderate to poor water quality.
• Water quality monitoring conducted at Bee Camp Creek and Olio Rd and Thorpe Creek and Cyntheanne Road for this Master Plan indicates:
• Chemical – Nitrogen concentrations were significantly higher in April, May, and June than all other sampling events at these locations. Phosphorus concentrations were higher at the Thorpe Creek and Cyntheanne Rd location but were still below water quality targets. E. coli concentrations exceeded the Indiana Water Quality Standard 86% of the time at both locations.
• Biological – Both sites in this area scored in the Excellent category at 27.5 (3rd of 10) and 28 (2nd of 10) respectively. The Thorpe Creek and Cyntheanne Rd site was sampled only during the spring as the site was dry during fall sampling efforts.
• Physical – Bee Camp Creek and Olio Rd received 6th highest overall QHEI score (59/100) while Thorpe Creek and Cyntheanne Rd scored 72/100 or 2nd highest overall. Thorpe Creek and Cyntheanne Rd scored significantly higher in the individual metrics associated with drainage area gradient and pool/riffle structure.
• Other water quality studies
• The Marion County Health Department completed water quality monitoring at 8 locations within this watershed between 1998 and 2002; 6 are within the planning area. E. coli levels were not monitored and nutrient and metal concentrations were either below detection limits or present in concentrations below water quality targets.
• The Hamilton County Health Department maintains 3 monitoring locations near Geist Reservoir to monitor water quality during the recreation season. The Indiana Water Quality Standard for E. coli was violated in the following locations: Fall Creek at Geist Park-64% of samples; Geist Reservoir at Olio Rd-0.07% of samples; and Geist Marina at Fall Creek Rd-no samples in violation.
• Indiana University monitored secchi depth in Geist Reservoir as a part of the Indiana Clean Lakes Program in 1991, 1996, and 2002.
• IDEM has monitored fish tissue at 3 locations (2 downstream of planning area) between 1985 and 2006.
• Fall Creek and Geist Reservoir are the only waterways in this watershed that are listed on the State of Indiana 303(d) List of Impaired Streams.
• Based on available land use data for this watershed, it is anticipated that water quality in some or all water bodies is likely impacted by elevated nutrient, bacteria, total suspended solids, and metals loads.
• Dry weather screening conducted by the Town of Fishers identified 99 outfalls (observed dry weather flow at 11 outfalls).

Exhibit 2-7b
Floodplains, Drainage & Flooding Concerns

Typical flooding of open fields and portion of Ringer Road.

Known Drainage Problems or Concerns

The following were drainage problems or complaints identified in the Thorpe Creek - Geist Reservoir Watershed by the Town of Fishers staff, recorded in the Town’s Drainage Complaint Database, or gathered during the Public Meeting. These include:

• Street Flooding (8):
  • Water ponds at Ringer Road just south of 116th Street (A14), at 3 locations along N. Georgia Road north of 96th Street (A12, A37, A38), at Brooks School Road north of Fall Creek Road (A35), in the turn lane and path near 106th Street and N. Windermere Boulevard (A33 & A34), and Landover Lane and Hawthorne Ridge intersection due to repaving (A3).
• Building Flooding (31):
  • There are approximately 30 single family residential structures in the Luxhaven and Lakeview neighborhoods that are in the floodplain of Fall Creek as determined by an overlay of the existing flood maps with an effective date of February 19, 2003 and the 2009 aerial photography. 1% annual chance flood depths range from 1 – 5 feet. All but 1 or 2 of these structures are also located in the floodway. One structure appears to be located in the floodway but on high ground above the BFE. This structure may or may not have been constructed in violation of the Indiana Flood Control Act if it is a residence. These neighborhoods are not safe areas in which to live during a flood (BR14-BR44).
  • County Parks building floods (Geist Park on Florida Road north of Fall Creek) (BR45).
• Localized Flooding (1):
  • Water stands in the ditch (106th Street and Geist Road)(F12).