7th Annual Technical Conference
Georgia Association of Floodplain Management
Legacy Lodge @ Lake Lanier Islands Resort
LESSONS LEARNED
The Flood of September 21, 2009 in Cobb County Georgia
March 28, 2012
Bill Higgins, P.E., CFM
Division Manager - Stormwater Management
Cobb County Water System
Two Hazard Mitigation Grants were awarded to
Uninc. Cobb Co. following the Sept. 21, 2009 flood:
One grant for 34 (later amended to 36) properties in Unincorporated Cobb
A second for 16 properties in the City of Powder Springs
..
this presentation will describe our courseprior to and following the award of those grants, and some of the lessons we learned
Statistics
794 homes flooded in Unincorporated Cobb
497 homes with 100-yr floodplain on all or part of property
297 properties were outside the 100-year floodplain
112 “Substantially Damaged” Buyout Grant includes
35 SD properties in floodplain
67 SD properties outside floodplain
Some 700 Homes flooded in the City of Austell
100 + Homes flooded in City of Powder Springs
Declarations
Chairman Sam Olens issued a countywide declaration -Monday evening (9/21/09)
Governor Sonny Perdue issued an Executive Order declaring
a State of Emergency in 17 counties including Cobb -Monday (9/21/09)
On 9/24/09 President Obama issued a Federal Disaster Declaration for 17 counties
:
Bartow, Carroll, Catoosa, Cobb,Chattooga, Cherokee, Coweta, Dekalb, Douglas, Fulton Gwinnett, Heard, Newton, Paulding, Rockdale, Stephens, and Walker.
History
In NE Cobb Co, the storm began at 6:30PM on Sunday evening 9/20/2009. The rain ended between 6:30PM and 7:00PM the following day (9/21/2009)
Community Development and Cobb EMA sent first responders to identify and assist flood victims
Soon became apparent over a thousand properties had been flooded including hundreds of destroyed homes
News media was heavily involved interviewing flood victims and government representatives, watching everything and
History
Immediately following the storm:
Cobb County SWM began visiting dams.
Gregg W. Hudock, P.E. of Golder Associates called offering help. We asked him to help us inspect dams which they did gratis.
Terri Turner, AICP, CFM of GAFM called offering help.
In less than a week Terri obtained commitments from 28
GAFM members to assist Cobb w/ R.S.D.E. damage assessments, which they did gratis
History
Terri also identified an individual consultant R.S.D.E. expert,
Ranko Pudar P.E. CFM, to instruct the class
The R.S.D.E. class was held between October 8 and October 10, 2009 for approximately 70 persons. Mr. Pudar offered this service to Cobb, as well as his subsequent efforts- gratis
Preliminary Damage Assessments of some 700 properties in Unincorporated Cobb were completed within 1 week.
By October 21, 2009 (one month after the flood), preliminary R.S.D.E. analyses were completed for all flooded properties in Unincorporated Cobb
History
October 21, 2009 - First public meeting held at the Cobb County Fire Station on Austell Road near Clay Road
We had to deliver some painful messages
We had no information for City of Austell residents and we could not help them
Substantially damaged homes within the 100-year floodplain could not be rebuilt without elevating
Substantially damaged home outside of the 100-year
floodplain would not be deemed eligible to participate in a Hazard Mitigation property acquisition grant
We would not be able to help everyone
History
Just prior to the October 21, 2009 Public Meeting, Brian McCallum of United States Geological Survey (USGS)
delivered some timely information which was supported by the National Weather Service (NWS).
The Sweetwater Creek watershed had received 22-inches of rainfall within a 24 hour period which equated to a 10,000 year frequency event.
The second Public Meeting held on October 26, 2009 went more smoothly.
Robert Holmes,
USGS’s National Flood
Program Coordinator stated…
“
Nationwide, given that our oldest stream gaging records span about 100 years, the USGS does not cite probabilities for floods that are beyond a 0.2 percent probability (500-year) flood.”History
From late October until January 10, 2010 we sorted through the flood damaged properties re-assessing and re-checking substantial damage estimates
On January 10, 2010 we submitted our grant applications
GEMA processed our applications within a month
FEMA was halted by the Congressional freezing of the
History
July 31, 2010 Federal Disaster Relief Funds were unfrozen
Mid-September 2010, Cobb received both grants
Grant Implementation
Coordination with GDOT, USACOE, SHPO, USF&WL already done during grant evaluation
Title Search
Environmental Assessments
Phase 1 EA
Asbestos and Lead Paint
Close Properties with clear titles (no liens)
Work to clear titles on upside down properties
Record Deeds and Deed Restriction
Procure Demolition Contractor
Demolish and Remove Structures
Grant Implementation
Set up to pay flood victims for the pre-flood value of their property ( home and land not lost contents)
“Pre-flood Value established by 2009 Tax Appraised Value
in www.cobbassessor.org
Many received Individual Assistance funds (up to $30K) from FEMA for emergency repairs and temporary relocation
All previous federal disbursements had to be deducted from sales price as a Duplicate of Benefit (DOB)
Grant Implementation
A year after the flood, many were upside down with
their mortgages
Some:
Used their IA relief checks for: food, furniture, clothes, new cars
Wanted FEMA to cover mortgage payments
Wanted FEMA to cover lost contents
Update Sweetwater Creek Floodplain
Floodplain study for Sweetwater was 23 year old and did notinclude this storm in the statistical record.
Maybe the 100-year floodplain is higher, which could make more victims eligible to participate in Grant
Subsequent study by Jacob, as reviewed by Dewberry
confirmed approx 3-ft higher 100-year floodplain
Making 33 more home eligible in Unincorporated Cobb and possibly double that number in City of Austell
FEMA will not deem these homes eligible until Letter of Final Determination issued
GEMA asserting homes can be made eligible according to premise of “Best Available Data”
Statistics
The rains returned water levels in the region’s
two largest reservoirs, Lake Lanier and
Allatoona Lake to pre-drought levels:
Lake Lanier rose by more than 3-ft to Elevation 1068 by September 25th and returned to full pool in October
Allatoona Lake rose to Elevation 853.25 on September 23, more than 13 feet above flood Pool at Elevation 840.
Statistics
In Cobb County, the following creeks reached
or exceeded the 500-year frequency event:
Sweetwater Creek
Noses Creek
Noonday Creek
Butler Creek, and
Statistics
On Sweetwater Creek near Austell…
High Water Marks showed peak stage of record at 30.8 ft
Previous peak stage recorded 7/11/2005) from Hurricane Dennis at 21.87 ft.
Peak Flow (31, 500 cfs) was more than double the previously recorded peak flow of record
Statistics
On the Chattahoochee River, the USGS gage
at Vinings recorded…
A Peak Stage of 28.12 feet
Peak Discharge of 40,900 cfs
Lessons learned – the ugly truth
-
20 inches of rainfall in less than 24 hours
Lessons learned – the ugly truth
Rather than accept the inevitable
consequences of a natural disaster, human
nature compels many people to get
State Route 41
@ Butler Creek
Lessons learned –“the ugly” truth…
Many expect local government to act as the
Lessons learned –“the ugly” truth…
After a flooding disaster the public could care
less about:
…how much it rained; or
…what frequency the rain event was; or
…how saturated the ground was; or
…how many culverts became clogged; or
…whether or not they should have had flood
insurance
All they want to know is…
Lessons learned – “the ugly” truth…
Many
…living in the floodplain still do not have flood
insurance
…do not understand what the FEMA floodplain
Lessons learned – “the ugly” truth…
Many
…private Dam Owners do not understand or do
not accept what their individual responsibilities
are…
Lessons learned – “the bad”…
The Computed 100-year Floodplain Elevations for Sweetwater Creek were 23 years old.
After Hurricane Dennis in 2005 a notification to buy flood insurance should have been sent or published.
Dam Owners should have been put on notice about their dam’s potential hazard to the public
The role of Government with regard to uninsured flooded
homes and existing dams needs clarification
The SWM Ordinances need work:
Substantially Damaged homes
Lesson learned - the good…
28 GAFM volunteers appeared and helped for a week RSDE inspections were completed within 1 week
RSDE assessments completed within 1 month
No dams failed
GAEPD Safe Dam’s Program
Storage Volume Purchase program
Development Standards
No one’s home included in previous buyouts flooded USGS Continuous Gage Network –allowed tracking
Alliances with U.S.G.S.,USACOE, GAFM & GEMA USGS: Gage Network & Storm Freq Estimates
USACOE: Field Surveyed High Water Marks
GAFM : 28 Volunteers for Damage Assessments
Progress to Date
In the 34 (later amended to 36) property grant for Uninc. Cobb (HMGP 1858-0013):
32 properties closed
3 properties withdrawn
1 property closing pending
29 homes of the 32 closed demolished
3 homes designated as historic sites by SHPO not yet released for demolition
Progress to Date
In the 16 property grant for the City of Powder Springs (HMGP 1858-0014):
12 properties closed, demolished and removed