Future condition and concerns for the planning area portion of the watershed 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.

• Existing condition runoff rates and corresponding restrictive release rates were proposed as part of the Stony Creek Watershed Master Plan done for the Hamilton County Surveyor’s Office. The proposed restrictive release rates have not been made a part of the ordinance at this time. The default release rates which currently apply to this watershed are much higher than the existing condition runoff rates that were calculated. Therefore, runoff in this watershed is expected to increase with development.
• No control on the 50% annual chance flood developed condition discharge has been or is in the Town or County current ordinances. Based on a study of the Williams Creek watershed in Hamilton County, development under the current ordinance allows for substantial increases in the 50% annual chance flood. Not only does the ordinance allow increases in the peak discharge but also in the duration of the flood. The 50% annual chance flood is typically the channel forming discharge for streams. When that flood frequency increases in discharge and duration, additional stream bank erosion typically occurs. Such erosion affects not only the stability of the bank and the safety of anything on the bank but the quality of the water as well.
• There are currently no structures in the existing floodplain area to be impacted. Any new development should be constructed with 2 feet of freeboard per the ordinance, thus protecting structure contents at least from a flood on the order of magnitude of a 0.2% annual chance flood.
• Development will add additional infrastructure which will need repairs or maintenance in order to not adversely impact drainage in the watershed. Maintenance of those portions of the system that are or will be added to the regulated drain or regulated subdivision roles can be accomplished with assessments. Other portions that are under the Town’s jurisdiction can be addressed with stormwater utility funds. The level of funds that will be available may or may not be adequate to cover all of the maintenance required.
• Impact on roads/bridges - no change expected.
• This watershed is currently agriculture (53%) however; according to future land use data this will dramatically change to low-density residential development (estimated increase from 30% to 74%) and commercial development (estimated increase 0% to 26%). As a result of this dramatic land use change, imperviousness is estimated to increase from 47% to 78% which is indicative (typically) of poor water quality.
• Based on future land use data and anticipated change from agriculture to residential and commercial land uses, it is expected that water quality in some or all water bodies will likely become more impacted by elevated nutrient, bacteria, total suspended solids, and some metals loads.
• Current Stormwater Management Ordinance requires post- construction BMPs to remove 80% Total Suspended Solids (TSS) from stormwater runoff. It is assumed that other pollutants of concern will be captured to some extent with TSS. Elevated E.coli violations, as noted in 303(d) Impaired Streams List for William Lehr Ditch, are not addressed.