Hamilton County Soil and Water Conservation District

Wet Weather Initiative

Meeting Minutes

August 22, 2002

Present: Tom Ryther, Chair; Cory Chadwick, HCDOES; Nancy Ellwood, MCWC; Bob Jansen, MVCD; John Hunter, LWVCA; Bob Caudill, HCGHD; Jeff Leedy, HCPWD; Barbara Quinn, CAGIS; Andy Swift, CAGIS; Marty Umberg, MSD

CAGIS STORMWATER RUNOFF CALCULATOR - Barbara Quinn and Andy Swift
Storm Water Run-off Calculator In Development by CAGIS (Cincinnati Area Geographic Information System)

Over the last 2 years, CAGIS initiated a project to developing a system to estimate storm water run-of from individual parcels of land. The purpose is to enable permitting agencies quickly and conveniently to assess the impact of proposed land use changes on storm water run-off. The estimates are based on a storm water model that requires several GIS data layers: a Digital Elevation Model, a Surface Drainage Network, Detailed Watershed Boundaries, Soil Attributes, and Impervious/Pervious Surfaces Data. The work is being carried out on a part time basis by CAGIS staff and interns in a collaborative effort with USEPA Research.

Andy Swift of the CAGIS staff has provided the following description of the project: "Impervious/Pervious Surfaces is a key GIS data-layer, since storm water run-off volume calculations are highly dependent on the percentage of impervious surfaces. The creation of this data layer has experienced three stages. In the Stage 1 of impervious layer creation, only line vector features were available, which cannot be used to calculate areas of impervious surfaces. Modeling was used to create polygons from lines of 1996 planimetric features. This is estimated to be 60-70% accurate, a workable starting point for impervious surfaces data. In the Stage 2 of impervious layer creation, remote sensing was used to classify Ikonos 4-meter resolution, multi-spectral satellite imagery, into an ArcInfo Grid format land cover layer. This data layer included six different land cover classes: impervious surfaces, trees, grass, water, agriculture and soil. In the Stage 3, in order to help assess the usefulness of hand-digitized impervious surfaces (versus remotely sensed data, which costs much less time and labor consumption), a detailed layer of impervious surfaces will be created in a small pilot area.

In addition to data, CAGIS is developing a Stormwater Run-Off Calculator. The Run-off calculator is TR-55 based ArcView Extension. This tool allows users to select parcels, and get back estimated storm water run-off volumes. It has the ability to do before/after calculation on a 'proposed development' theme. Currently, we are doing accuracy assessment. This tool does the TR55 calculations correctly. The next step is to tie it to real world runoff data from a study and to compare model results for different data types.

With currently existing data and tools CAGIS staff could help answer such spatial questions as: If there is a toxic spill, which downstream parcels might be affected?
If there is a flood, which upstream parcels contribute to the flooding, and in what relative amounts?
If there is some area proposed to be developed, how much storm water runoff volume is created as a result?
If stream x rises to this elevation, in this area, what parcels might be affected?
What are the watersheds in the county that need protection, and which can handle more paved surface area?

Our current goal is to develop data and tools to allow CAGIS users to estimate storm water runoff volume. We don't currently have the data or modeling tools to deal with time and speed issues, (like predicting the behavior of flood bubbles). For example we will not be able to answer questions like: If there is a rain event of x inches, per hour, how will the water level of some specific stream be affected? If x amount of rain falls in a day, which areas would be predicted to flood?"

HAMILTON COUNTY STORMWATER STUDY STEERING COMMITTEE UPDATE - Jeff Leedy
The Steering Committee heard plans for an education campaign to inform the public about plans for the formation of a Hamilton County Stormwater District. A report was made on a cost of service analysis and a financial plan for the district. The Executive Committee has been formed and will gauge the level of interest among the political jurisdictions within the County for joining the proposed district. Response so far is limited but encouraging.

Ohio EPA has posted a draft General Permit for Phase II compliance on its website. Initial reaction is that the draft goes beyond the USEPA requirements but is a useful basis for soliciting comments.

STREAMSIDE AND STORM WATER MANAGEMENT WORKSHOP - Tom Ryther for Brian Bohl
A Streamside and Storm Water Management Workshop will be held on September 12, 2002 at the Mill Race Lodge in Winton Woods County Park. Cosponsors - HCSWD, BCSWD, USEPA. The workshop is intended for elected/public officials and their immediate staff facing compliance with USEPA Phase II NPDES permitting but has been opened to other interested parties. Cost is $30. The registration deadline has been extended to August 30, 2002. Call 513-772-7645 for information.

COMMITTEE REPORTS
The Watershed Signage Committee announced its next Committee meeting will be on September 18. Call Nancy Ellwood (513/563-8800)

UPDATES

Hamilton County Soil & Water Conservation District will have its Annual Meeting on Thursday, September, 19, 2002 at the Vinoklet Winery on old Colerain Avenue. The meeting starts at 6:00 p.m. and will include election of supervisors, awards and displays. Deadline for reservations is September 6.
The Mill Creek Restoration Project website is up and running at www.millcreekrestoration.org. MCRP email addresses have been changed; for example, Lora Alberto's is now <lora@millcreekrestoration.org>.
The Mill Creek Watershed Council (Nancy Elwood) has secured a keynote speaker, Mr. Wally Wilton, for the "Floodproofing Workshop and Exhibition" to be held Saturday, November 9 at Tech-Solve in Bond Hill. Mr. Wilton is a nationally recognized expert on flood-proofing.

NEXT MEETING
The next meeting of the Wet Weather Initiative will be on Thursday, September 26, 2002 at 9:30 a.m. at HCDOES, 250 Wm. Howard Taft Rd. An agenda will be distributed by e-mail before the meeting.

FUTURE MEETING DATES
Future Wet Weather Initiative meeting dates were confirmed as follows: October 24, 2002; November 21, 2002; no December meeting; January23, 2003. All meetings are at 9:30 a.m. at HCDOES, 250 Wm Howard Taft Rd.