Understanding future conditions and the associated stormwater concerns is critical to the successful development and ultimate implementation of a Stormwater Master Plan. It becomes even more critical in a community that is growing as quickly as the Town of Fishers. This Chapter describes the anticipated future land uses and regulations or projects. It also identifies the severity and extent of problems that could arise as a result.

Unless otherwise noted in the text, the discussion on future condition focuses on the Town of Fishers planning area portion of the watershed only. This area is based on the Town’s planning and zoning jurisdiction bordered by White River (west), 146th Street, 141st Street, 136th Street, and I-69 (north), Atlantic Road (east), and 96th Street (south). Within each watershed description is a summary of the extent and severity of anticipated future surface water quantity and quality concerns based on information gathered from public input, local agency input, review of previous studies, and data collection. The following information is provided for each of the 9 12-digit HUC watersheds in the Town of Fishers:

• Impact of existing ordinance allowable release rates on discharges
• Impact of rare flood events – would events on the order of the 0.2% annual chance flood damage additional residential/commercial structures?
• Infrastructure replacement/maintenance
• Impact on roads/bridges – is development expected to increase flow depths at bridges?
• Changes to land use and imperviousness
• Anticipated pollutant loadings and stormwater pollutant removal requirements

Nine watersheds drain land in the Town of Fishers.

Use the list below, or select the watershed from the graphic on the left to read about future conditions for each watershed.  A future land use/zoning map (Exhibit 3-x) has been prepared for each of the 9 watersheds.

1. Mallory Granger Ditch-White River Watershed
2. Vestal Ditch-White River Watershed
3. Carmel Creek-White River Watershed
4. William Lehr Ditch-Stony Creek Watershed
5. Sand Creek-Mud Creek Watershed
6. Headwaters Mud Creek Watershed
7. Thorpe Creek-Geist Reservoir Watershed
8. Flatfork Creek-Fall Creek Watershed
9. McFadden Ditch-Lick Creek Watershed

Current default allowable release rates are set higher than calculated existing condition release rates in the Flatfork Creek-Fall Creek, Headwaters Mud Creek, and Sand Creek-Mud Creek watersheds. As a result, discharges are expected to increase in many of the tributaries in these watersheds. In the Mallory-Granger Ditch-White River and Thorpe Creek-Geist Reservoir watersheds, current allowable release rates are low enough to theoretically prevent increases in the 1% and 10% annual chance flood peaks but are not low enough to provide the factor of safety included in the Stormwater Management Ordinance to account for factors that are not modeled.

Because there is no control on the 50% annual chance developed condition discharge in the Town ordinance, future development in the watersheds that are expected to develop further could substantially increase the 50% annual chance flood peak discharges and flood durations. Additional stream bank erosion will likely occur as a result. Such erosion will affect not only the stability of the bank and the safety of anything on the bank but the quality of the water as well.

Dramatic land use change is anticipated in the Flatfork-Fall Creek, McFadden Ditch-Lick Creek, and William Lehr Ditch-Stony Creek watersheds. Future land use data from the Town of Fishers Development Department anticipates that agricultural uses in these watersheds will be replaced by residential, commercial, and industrial uses. Similarly, estimated imperviousness, based on the change in land use for these watersheds, will increase as much as 30-50% affecting water quality and quantity.

Increased development in the Flatfork-Fall Creek, McFadden Ditch-Lick Creek, and William Lehr Ditch-Stony Creek watersheds will result in the need for additional infrastructure and therefore additional maintenance or repair funding to keep the systems functional. Legal drain assessments or stormwater utility fees may or may not be adequate to cover all the costs for those systems under the Town or County Surveyor’s Office jurisdictions.

Existing bridges in the Flatfork Creek-Fall Creek Watershed as well as along Mud Creek in the Sand Creek-Mud Creek and Headwaters Mud Creek watersheds have the potential for increased depths of overflow as development occurs in the watersheds.

Impacting all watersheds in the Town of Fishers is the current Stormwater Management Ordinance. This Ordinance requires post-construction BMPs to remove 80% TSS from stormwater. It does not specifically target other pollutants of concern such as nutrients, metals, or bacteria or water quality violations identified on the 303(d) Impaired Stream List.

Similar to understanding existing conditions and concerns (Chapter 2), the future conditions and associated concerns are as important since they too become the foundation for the goals and performance criteria (Chapter 4); the recommendations to address stormwater problems (Chapter 5); and implementation plan (Chapter 6) of this Master Plan.