Federal Emergency Management Agency_DFIRMTHE CITY OF ( T' \ Dubuque
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Masterpiece on the Mississippi 2007
VIA EMAIL
Kevin C. Long, Acting Chief
Engineering Management Branch
Mitigation Directorate
Federal Emergency Management Agency
500 C Street SW
Washington DC 20472
Beth Freeman, Administrator
FEMA Region VII
9221 Ward Parkway, Suite 300
Kansas City MO 64114 -3372
Dear Mr. Long and Ms. Freeman:
Service
Office of the Mayor and City Council
City Hall
50 West 13 Street
Dubuque, Iowa 52001 -4864
(563) 589 -4120 office
(563) 589 -0890 fax
August 25, 2010
SUBJECT: City of Dubuque Technical Appeal of FEMA Preliminary DFIRM
This letter provides the initial documentation from the City of Dubuque constituting a
technical appeal of FEMA's preliminary DFIRM for the community. This letter transmits
preliminary findings on behalf of the impacted property owners and lessees. The City of
Dubuque requests an extension of our 90 -day technical appeal period to enable our
consultants to complete their analysis. A hard copy of this letter and its enclosures will
follow.
As you are aware, after reviewing FEMA's preliminary DFIRM sent to the City in July
2009, City staff found extensive errors in the mapping of both existing and new flood
plain areas. The City's issue with the preliminary DFIRM is the new areas designated
as being in a Zone A. Zone A designation does not provide base flood elevations, but
does carry a mandatory insurance requirement for those property owners with
mortgages.
In particular, the City of Dubuque is extremely concerned by the inclusion of over 1,700
structures, mainly on the North End, in a Zone A that has never been designated as a
flood plain in the past. The City currently has approximately 70 structures in designated
flood plains.
People Integrity Responsibility Innovation Teamwork
City of Dubuque Technical Appeal of FEMA Preliminary DFIRM
Page 2
The North End of Dubuque is a predominantly older, low to moderate income
neighborhood, where the City has promoted redevelopment and homeownership for
many years. The designation of this area as a Zone A will reverse years of progress
and likely contribute to disinvestment in this crucial area of our community.
The City of Dubuque is on record as being supportive of FEMA's project to update the
nation's flood maps. However, the methods used to determine the Zone A areas in
Dubuque are not up to the standards that any community would be held to by FEMA to
make changes to our flood plain maps, either currently or in the future. City staff has
found errors in FEMA's preliminary DFIRM that include the Julien Dubuque Monument
on top of a bluff being in a 100 -year flood plain, that a Zone A area is mapped going up
the side of a bluff, that the elevation of the 100 -year flood is 20 feet higher on the right
side on the bank than it is on the left side, to name just a few.
FEMA did agree to use the City's two -foot contour data from our GIS, but indicated the
revised DFIRM would likely not be available until after our 90 -day appeal period has
expired on August 26, 2010.
Consequently, the City of Dubuque has retained the services of CDM to do a more
detailed analysis of the City's North End and Bee Branch areas as well as a segment of
the North Fork of the Catfish Creek as a technical appeal of FEMA's preliminary DFIRM
for the community. The consulting firm will complete work by the end of the August.
This is an additional expense to the City of $50,000 that the citizens of Dubuque will
have to spend to insure that the City has the most accurate flood plain map possible.
The City continues to work with FEMA officials as well as keeping our elected
representatives at the State and Federal levels informed on our efforts to have the most
accurate DFIRM possible for our community.
Thank you for your attention to this matter. Please feel free to contact Planning
Services Manager Laura Carstens with any questions or information requests at
563.589.4210 or IcarstenAcityofdubuque.orq.
Sincerely,
Roy D. Buol
Mayor
Enclosures
4‘,/
cc: City Council Members
Michael Van Milligen, City Manager
Service People Integrity Responsibility Innovation Teamwork
City of Dubuque Technical Appeal of FEMA Preliminary DFIRM
Page 3
Barry Lindahl, City Attorney
Tim O'Brien, Assistant City Attorney
Teri Goodmann, Assistant City Manager
Laura Carstens, Planning Services Manager
Kyle Kritz, Associate Planner
Gus Psihoyos, City Engineer
Deron Muehring, Civil Engineer
Roger Benson, FEMA Region VII
Melissa Janssen, FEMA Region VII
Rick Nusz, FEMA Region VII
Bill Cappuccio, Iowa Department of Natural Resources
Anna O'Shea, Dubuque County Zoning Administrator/ Flood Plain Administrator
The Honorable Tom Harkin, U.S. Senate
The Honorable Charles Grassley, U.S. Senate
The Honorable Bruce Braley, U.S. House of Representatives
Sherry Kuntz, Legislative Aide, Senator Grassley's Office, Washington D.C.
Richard Bender, Senior Legislative Assistant, Senator Harkin's Office,
Washington D.C.
Dan Smith, Senator Harkin's Office, Cedar Rapids, IA
Linda Lucy, Senator Harkin's Office, Dubuque, IA
Mike Goodman, Legislative Director, Representative Bruce Braley's Office,
Washington D.C.
Pete DeKock, District Administrator, Representative Braley's Office, Davenport,
IA
John Murphy, Representative Bruce Braley's Office, Dubuque, IA
Amanda Wilson, AECOM, 2405 Grand Blvd, Suite 1000, Kansas City MO 64108
Service People Integrity Responsibility Innovation Teamwork
Memorandum
To: Deron Muehring, Engineering Department, City of Dubuque, IA
From: Susen Gali, CDM
Date: August 25 2010
Subject: Data Used for Developing the Bee Branch Watershed Preliminary
Floodplain Map
CDM has been tasked to develop preliminary floodplain mapping based on a detailed study
for the Bee Branch Watershed. This memorandum serves to present preliminary results and
present the data used and assumptions made for developing the preliminary floodplain
mapping.
1. Hydrology and Hydraulic Modeling
• In accordance with FEMA guidelines, CDM is using a hydrology model that they built
in 2004 using HEC -HMS; a computer program developed by the US Army Corp of
Engineers. The HEC -HMS model was updated to reflect the Carter Road Detention
Basin that was constructed in 2003 and the W. 32nd Street Detention Basin that was
constructed in 2008 -09. Per FEMA guidelines, the 100 -year 24 -hour storm was used for
producing the peak runoff flows.
• In accordance with FEMA guidelines, CDM is using a SWMM 4, hydraulic model that
they built in 2004. The SWMM 4 computer model that was developed by the US EPA
was used for routing the hydrographs through the storm sewer conduits.
• 594.3 elevation was used for the Mississippi River stage as the is the normal, or 50%
exceedance, river stage based on data from the US Army Corp of Engineers.
• CDM is in the process of updating the 2004 hydrology and hydraulic models in
accordance with the FEMA's guidelines, policies and specifications.
2. Topography Data
• 2009 electronic contour data from City of Dubuque was used for delineating the
floodplain. The contours are 2 -foot contours with a stated accuracy of one foot Based
1
Bee Branch Watershed
August 25th, 2010
Page 2
on City survey data, the accuracy of the City's contour data has been found to be
within a half foot.
3. Assumptions
• Consistent with the US Army Corp of Engineers' conclusion, the Bee Branch
watershed peak stages are independent of Mississippi River peak stages.
• Free outfall from the 16th Street detention basin to Mississippi River
• Levee along the Mississippi River is certified and the Mississippi River peak stages
will not have impact on the Bee Branch Watershed.
• 100 -year 24 -hr is assumed to be the critical storm for the Bee Branch Watershed.
Further critical duration analysis is required to identify the critical storm which
produces the peak discharges and stages for the watershed. Depending on the
identified critical storm the floodplain boundary will change for the watershed.
4. Preliminary Findings
• The preliminary peak runoff flows predicted using the detailed HEC -HMS model is
significantly less than the flows predicted by FEMA using approximate regression
equations.
• The preliminary flood plain limits for the Bee Branch are significantly less than the
limits reflected in the DFIRM currently being considered for adoption by FEMA. This
could be attributed to the decreased peak flows and the use of 2 -foot contours utilized
by CDM versus the 10 -meter contours utilized by FEMA.
2
600
1200
2,400 Feet
1 1 inch =692 feet
Bee Branch Watershed (Downstream Reach)
Preliminary Floodplain Map
Preliminary100Yr Floodplain (CDM)
SH FA 2009 Bee B ranch (FEMA)
1