WATER
RESOURCES
Evaluating the Natural and
Beneficial Functions of Floodplains
Amy Bergbreiter PE CFM & Pete Wright PE
GAFM 2015
Word Association: Floodplain
Source: Risk Map Vision
Word Association: Floodplain
Source: http://www.floods.org/PDF/WhitePaper/ASFPM_NBF%20White_Paper_%200908.pdf
Not a New Concept…
EO 11988 (1977)
“Each agency shall provide leadership and shall take action to
reduce the risk of flood loss, to minimize the impact of floods on
human safety, health and welfare, and to restore and preserve the
natural and beneficial values served by floodplains in carrying
out its responsibilities”
EO 13690 (2015)
“The result of these efforts is the Federal Flood Risk Management
Standard (Standard), a flexible framework to increase resilience
against flooding and help preserve the natural values of
floodplains.”
In the News
Once Upon a Time…
Photo Source: http://www.dcr.virginia.gov/natural‐heritage/natural‐communities/image/pih‐photo3‐500.jpg
Present Day
History of a Floodplain
Original prehistoric floodplain soil surface and channel
Channel enlarges due to increased
runoff, sediment accumulates
Channel continues to increase in size, more sediment
New floodplain forms, T1 becomes a sediment source
Channel laterally migrates,
T1 continues to erode
More of the same
Source: Leigh, Davd. Morphology and Channel Evolution of Small Streams in the Southern Blue Ridge Mountains of Western North Carolina (2010) How did we get here?
Agricultural Practices
Urbanization
Clearing floodplains
Forested Versus Developed
Forested Watershed (cfs)
600
500
400
400
300
300
200
200
100
100
0
0
0.00
0.00
0.20
0.20
0.40
0.40
0.60
0.60
0.80
0.80
1.00
1.00
Forested Watershed (cfs)
Developed (cfs)
Forested Watershed (cfs)
1.20
1.20
1.40
1.40
How do we fix it?
There is continually evolving approach…
600
Reduce Peak Flow
500
Reduce Flow for Frequent Events
400
Reduce Runoff Volume
200
300
100
<Something else?>
0
0.00
0.50
Forested Watershed (cfs)
1.00
Developed (cfs)
1.50
How do we fix it?
There is continually evolving approach…
600
Reduce Peak Flow
500
Reduce Flow for Frequent Events
400
Reduce Runoff Volume
200
300
100
<Something else?>
0
0.00
0.50
Forested Watershed (cfs)
1.00
Developed (cfs)
1.50
How do we fix it?
There is continually evolving approach…
600
Reduce Peak Flow
500
Reduce Flow for Frequent Events
400
Reduce Runoff Volume
200
300
100
<Something else?>
0
0.00
0.50
Forested Watershed (cfs)
1.00
Developed (cfs)
1.50
How do we fix it?
There is continually evolving approach…
600
Reduce Peak Flow
500
Reduce Flow for Frequent Events
400
Reduce Runoff Volume
200
300
100
<Something else?>
0
0.00
0.50
Forested Watershed (cfs)
1.00
Developed (cfs)
1.50
Will this solve our Problems?
Camp Creek Watershed
• <Slides Introducing Camp Creek
Watershed>
Camp Creek @ Lilburn City Park
PreDevelopment vs. Today
How do we fix it?
Reduce Peak Flow
How do we fix it?
Reduce Flow for Frequent Events
How do we fix it?
Reduce Runoff Volume
How do we fix it?
Something else?
Camp Creek Stream Project
Pre Project
Post Project
Old Channel
New Channel
Pre-Project vs. Post-Project
Word Association: Floodplain
Source: http://www.floods.org/PDF/WhitePaper/ASFPM_NBF%20White_Paper_%200908.pdf
Comparing Wetland Inundation
Post Project
Pre Project
20-Year Continuous Simulation
Questions?