No Adverse Impact - The Association of State Floodplain Managers

Report
May 22, 2012
ASFPM - San Antonio
Mike Moya, PE – Halff Associates
Brian Reis, PE – RPS Espey
Brian Wells, PE – MWM Design Group
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Purpose is to determine what Texas communities
are doing above the minimum FEMA standards
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Developed by members of TFMA & ASCE/EWRI
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On-line survey from Aug ‘11 to Feb ‘12
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Workshop was held Sept. ‘11 at TFMA’s fall
conference
 Activities
that could adversely impact
another property or community will be
allowed only to the extent that the
impacts are mitigated or have been
accounted for within an adopted
community-based plan
3
 Principle
developed
 NAI Toolkit
 Legal Aspects of NAI
 Coastal NAI funded by
NOAA
www.floods.org/
4
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Physical increases
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Peak flow rates
Frequency of bank full conditions
Stormwater pollution
Sediment transport (aggradation)
Etc.
Physical reductions
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Base flow
Infiltration
Sediment transport (degradation)
Etc.
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The NFIP Regulations mandate that participating
communities adopt and enforce at least the
minimum standards of 44 CFR 60.3
Reference: 44 CFR 59.2(c)

Communities may exceed the minimum standards
and are encouraged to do so
Reference: 44 CFR 60.1(d)
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When the NFIP was established in 1968, it was
decided that minimum development standards
would be required for participation

They were considered sufficient to establish a
balance between an acceptable level of flood risk
versus difficulty in conducting the local program
Goal: Keep the program as simple as possible so
more communities will enroll
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Even with the minimum FEMA standards, flood
damages in the United States have continued to
increase
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“No Adverse Impact floodplain management is
where the action of one property owner does not
adversely impact the rights of other property
owners, as measured by increased flood peaks,
flood stage, flood velocity, and erosion and
sedimentation.”
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Located between Austin and San Antonio
Population 45,000
Home of Texas State University
San Marcos River
◦ Popular recreation area
◦ Home to several threatened or endangered
species
 Texas Blind Salamander
 Fountain Darter
 Texas Wild Rice
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Will be subject to EPA MS 4 regulations
Amarillo
FW D
El Paso
Austin
SA
Laredo
Brownsville
Houston
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25-year and 100-year are to be conveyed /
contained within ROW or drainage easements
Peak flow shall not cause increased inundation
of any building or roadway for the 2-, 5, 10-,
25-, 50- or 100-year storm frequencies.
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Fully developed conditions upstream.
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Detention is required for the 2- and 25-year
frequency storm events.
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Development within the floodplain shall not
increase the base flood elevation by more
than 1 foot.
Development within the floodway shall not
result in any increase in the base flood.
Floodplain alterations shall not create an
erosive water velocity (> 6 fps) on- or offsite.
San Marcos
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Limits on impervious cover
◦ Slopes (i.e. <15%, 15% to 25%, > 25%)
◦ Special areas: Edwards Aquifer, SM River Corridor
◦ Additional restrictions: water quality and buffer
zones
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Permanent BMPs
◦ Edwards Aquifer - limits increase in TSS to 20%
◦ SM River Corridor - capture first ½ inch
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San Marcos Comprehensive Planning
In progress
Land use suitability analysis
Identification of environmental metrics
Develop new sustainability standards: detention,
drainage, erosion, sedimentation control, archeological
site protection, etc.
◦ Consideration of Habitat Conservation Plan Goals
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Habitat Conservation Plan, December 2011
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Result of the EA Recovery Implementation Program
Identifies species and habitat
Identifies biological goals
Includes ‘take’ coverage
Activities required to minimize impacts
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USFWS to issue Incidental Take Permit based on HCP
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Permittees
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San Marcos
New Braunfels
Texas State University
Edwards Aquifer Authority
San Antonio Water System (SAWS)
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A collaborative, consensus-based stakeholder process.
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Plan to protect the federally-listed species affected by the
management of the Edwards Aquifer and other activities.
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The goals of the HCP include contributing to the recovery
of these species.
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Restoration of Texas Wild-Rice
Expanded program of monitoring water quality
Management of recreational use
Management of aquatic vegetation and litter
Control non-native and predator animal
species
A program to register, permit and evaluate
septic systems
Reduce impacts of IC through BMPs/LID
Etc.
The Corridor Development
Certificate Process (CDC)
affirms local government
authority for local floodplain
management and establishes
a set of Common Regional
Criteria and procedures with
the goal of minimizing
flood risks along the
Trinity River Corridor in
north central Texas
The Corps Regional Environmental Impact
Statement Trinity River and Tributaries –
1988 (TREIS) determined that the
cumulative impact of allowing individual
development projects in the Trinity River
floodplain could be both measurable and
significant.
Corps of Engineers Record of Decision (1988)
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No rise in the 100-year or SPF elevation for
the proposed condition will be allowed.
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The maximum allowable loss in storage
capacity for the 100-year (0%) and SPF (5%)
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Alterations in the floodplain may not create
or increase an erosive water velocity on or
off-site.”
Trinity River Steering Committee, facilitated by
the NCTCOG.
 Statement of Principles for Common
Permit Criteria (January 1988)
 Resolution for a Joint Trinity River Corridor
Development Certificate Process (December
1988)
 Regional Policy Position on the Trinity River
Corridor (January 1989).
 First edition May 1991
Common Regional Criteria
 No increase in the 100-year flood water
surface elevation (within 0.04 feet) and no
significant increase in the Standard Project
Flood water surface elevation
 A maximum allowable decrease of valley
storage in the 100-year flood and
Standard Project Flood discharges of 0.0%
and 5.0%, respectively
 No creation, or significant increase, in erosive
water velocity on-site or off-site
Benefits
 Common Regional Criteria
 Hydrologic modeling based on year 2050
Upper Trinity River watershed development
 Hydraulic model incorporating CDC permitted
floodplain development
 U.S. Army Corps of Engineers technical review
 Regional review and comment
 Guarantee of local control of floodplain
development decisions
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Questions
1.
2.
3.
4.
5.
6.
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What standards apply to quantify adverse impacts?
What is considered to be an insignificant impact?
What mitigation measures are required?
Which storm events are regulated?
What physical / chemical properties are regulated?
What specific challenges have you encountered?
50 participants
Communities varied in size
NFIP Standards
68.0%
Peak Flows
60.0%
Floodplain Elevations
72.0%
Other
25%
Yes
Yes
Velocity and TSS
18.0%
0%
Yes
50%
75%
100%
50 respondents
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No Policy
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No increase allowed in Zone AE
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No rise in floodway
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Peak: 0 cfs – 10 cfs or 0% - 2%
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Elevation: 0 ft. – 1.0 ft
1 foot rise
no rise
0 cfs
0.00 feet
87.5% 
On-Site Detention
On-Site Retention
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16.7%
DS Channel Improvements
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50.0%
Valley Storage
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39.6%
Regional Detention
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58.3%
Fee in Lieu
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20.8%
Other
16.7%
0%
25%
n/a
50%
75%
100%
48 respondents
2-year
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100.0% 
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n/a
36.0%
5-year
12.0%
10-year
46.0%
25-year
40.0%
50-year
18.0%
100-year
250-year 0.0%
500-year
4.0%
PMF
8.0%
Other
2.0%
0%
25%
50%
75%
100%
50 respondents
Water Quality
46.2%
Stream Erosion
TSS
velocity
64.1%
Base Flow
HCP
12.8%
Infiltration / GW recharge
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10.3%
Sediment Transport
30.8%
Wetlands/Riparian Zones
43.8%
Other
n/a
7.7%
0%
25%
50%
75%
100%
39 respondents
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Educating developers, engineers, and politicians
Retention / Detention standards
Using preliminary data to regulate
New FEMA flood maps
Conflicting regulations of adjacent
communities/districts
Defining “significant” impacts to upstream and
downstream properties
Lack of enforcement
Consistency in Engineering methodologies
Regulating multiple storm frequency events
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Diane Calhoun
Rob Connell
W. H. Espey
Nefi Garza
Steve Gonzales
Steve Graham
John Hewitt
Romin Khavari
Melinda Luna
Sharon Mattox
Sam Riley Medlock
Mike Moya
Michael Newman
Brian Reis
Roy Sedwick
Brian Wells
TFMA
FEMA Region VI
AAWRE, President-Elect
City of San Antonio
ASCE - San Antonio
San Antonio River Authority
TFMA Assistant Workshop Coordinator
City of Grand Prairie
TX Section EWRI, Chair
Vinson & Elkins, LLP
ASPFM
TFMA Workshop Coordinator (Halff Assoc.)
City of Temple
TFMA Workshop Coordinator (RPS Espey)
TFMA
TFMA Assistant Workshop Coordinator
EQ Recharge Zone
San Marcos

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