Johnson County Flood Warning/Flood Forecasting: Feasibility Study
Project Overview
In August 2002, the Johnson County Stormwater Management Program (SMP) completed
a study to determine the feasibility a flood warning/flood forecasting system in
Johnson County, Kansas – and if determined to be feasible, develop an
implementation plan and to identify the potential costs to develop such a
system. The basis for the study was the existing rain and stream gage network in
the County. In 1999 the Johnson County Stormwater Management Program initiated a
significant expansion to the existing rain and stream gage network that at the
time was located primarily in Overland Park, Kansas and Jackson County,
Missouri. The expansion covered a significant portion of Johnson County and was
completed to provide a data collection system and the foundation for developing
and implementing a floodwarning system, if desired or required.
Johnson County SMP staff managed and directed the overall effort. To ensure that
the needs of the Johnson County communities were met, a steering committee
comprised of city representatives from Mission Hills, Fairway, Overland Park and
Merriam, and representatives from the Johnson County Emergency Management and
Stormwater Management Programs was formed. Each steering committee team member
provided unique experience in the area of flood preparation and assisted in the
development of this study.
Key Findings
1. Based on the significant interest by
Johnson County communities combined with the extent and capabilities of the
existing rain and stream gage network in the County, a floodwarning/flood
forecasting system is feasible for Johnson County.
2. Based on the interest by communities in the Kansas City
Metropolitan area, combined with the extent and capabilities of the existing
rain and stream gage network in the region, a regional floodwarning/flood
forecasting system should be considered.
3. Numerous communities expressed interest in participating in
a regional system that could decrease the number of multiple, redundant
activities performed by individual communities.
4. Multiple local, regional, state and federal agencies
expressed an interest in being involved in and supporting a regional
floodwarning/flood forecasting system.
5. Multiple Johnson County communities recognize
floodwarning/flood forecasting as a practical and cost-effective alternative to
structural improvements.
6. An implementation plan can be developed for Johnson County
to initiate development of a floodwarning/flood forecasting system without
compromising the development of a regional floodwarning/flood forecasting
system.
7. Johnson County should continue to enhance and fund the
floodwarning system “backbone”. The backbone consists of the basic rain and
stream gage data collection network, and the data transmission and management
system necessary for the basic operation of the system. The total capital cost
for the backbone system to support a full countywide floodwarning system is
approximately $800,000. The annual recurring costs (which include operation,
maintenance, training, exercising the system, and outsourcing operation of
threat recognition and water level forecasting) are estimated to be
approximately $160,000 in 2004 dollars. It is recognized that it may be many
years, if ever, before a full countywide floodwarning system is required.
However, the steering team felt it was important to identify this cost now.
8. Each city will be responsible for the desired floodwarning
system/components needed – these systems/components include the locating,
design, construction, maintenance and operation of specific floodwarning
activities including flashing lights, automated gates and other features
necessary to warn the public of flooding conditions.
9. Johnson County should evaluate the potential for
watershed-based and/or countywide 24x7 flood forecasting services/support. At
this time it appears that outsourcing is the most cost-effective method for
providing this service/support.
10. The inventory of the existing rain and stream gage network
showed that the system requires an additional eight rain and stream gages to
function at a service level capable of supporting the countywide flood warning
system based on the currently identified needs.
11. The critical floodwarning system requirements identified by
the cities include location specific forecasting, basic transmission network
infrastructure, and a system that provides opportunity for future automation.
Recommended System Enhancements
The recommended system backbone, which includes elements that offer broad
benefit throughout the county, provides fundamental goods and services required
for an effective and efficient flood warning system. The existing backbone
system consists of 78 rain and stream gages, an ALERT radio single frequency
data transmission system, and a DIAD VisorTM data management system. Based on
the backbone system evaluation, the following enhancements are recommended:
• Add gage-adjusted radar rainfall with alarms.
• Add stream gages at eight locations.
• Upgrade the ALERT radio transmission system to incorporate dual-frequency
store-and-forward repeaters.
• Promote the use of NOAA weather radio by the cities and the residents. This
system provides wide-spread public notification.
• Provide an automated threat recognition system tool. The County should select,
and make available and cost effective for use by a city that desires to do so, a
computer-aided threat recognition and notification software package.
• Provide a template emergency response and preparedness plan for use by the
cities within Johnson County (and if applicable, the region).
• Provide site-specific water level forecasting services. The ability to
forecast water levels at specific locations on streams was identified by many
beneficiaries of flood warning as a critical need. However, streams within the
County cross political boundaries, so developing the capabilities within one
city and not the adjacent ones is inefficient. Accordingly, the backbone plan
should include capability to provide such forecasts at multiple locations.
However, the County should select and provide the service and tools with funding
for application from individual cities..
• Continue funding for website sharing information with the public. The
currently funded website
(www.stormwatch.com) is used widely as a source of real-time flood
information. This website is hosted by the City of Overland Park, financially
supported by the County and is useful for all Johnson County cities and others
in the Kansas City Region if applicable.
Summary
The proposed menu of services is a comprehensive list of potential countywide
flood warning system components. Over the next several years the cities and the
County could begin to integrate recommended backbone components. The recommended
system enhancements could be implemented as part of existing SMP projects or as
stand-alone improvements pending available funding.
If a threat recognition system is developed such a system will require
individual cities to identify potential flooding locations, and identify
specific actions required to maximize early threat recognition. Development of
this type of system would be aided by a 24x7 monitoring.
Improvements identified within this report assume continued coordination with
local, state, and federal organizations within the region, which currently own,
operate, or review flood warning information. As part of the implementation of
this report the County should explore join funding and grant opportunities from
potential funding sources identified within the appendix of this report.
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JOHNSON COUNTY STORMWATER MANAGEMENT PROGRAM
1800 W. 56 Highway
Olathe, KS 66061
Phone: (913) 715-8333
Fax: (913) 715-2453