National Flood Policy—ASFPM 2015 Recommendations
M. Arid Regions
M.1. Utilize the best available techniques to
identify and quantify the risk of flooding, erosion
and debris flow hazards in arid regions, including
alluvial fans and post-wildfire conditions. Also see
F.18 and N.1.
M.2. (a
Use new science and technology to update
hydrologic and hydraulic methods or models for
arid regions projects. Encourage the use of
stochastic numerical models to better simulate
location, extent, and depth of flooding in areas of
flow path uncertainty. Also see A.4
M.2. (b) In the past , delineation techniques have
failed to recognize flow path uncertainty in arid
regions. This resulted in unintentionally reducing
the extent of predicted Special Flood Hazard Areas
and/or under predicting volumes and depths of
flooding and debris. After major flood-disaster
storm events cause erosion and new flow paths
that change flood risks vertically and/or
horizontally, provide a low-cost LOMC process for
NFIP communities and to update FIRMs (44CFR
Part 65).
M.3.(c) Development should be discouraged in
areas subject to flow path uncertainty, erosion and
debris flow, in arid regions and other geographies
M.3. Develop floodplain management techniques
which address wildfire, flood and erosion cycle
hazards experienced in the arid regions. Best
management practices will vary as appropriate
amongst the arid regions. Revise NFIP definitions,
regulations, and elevation requirements and arid
regions for existing Special Flood Hazard Area
zones: approximate Zone A in shallow sheet
flooding less than 1-foot deep, Zone AH in true
ponding areas, and Zone AO where depth exceeds
3 feet, redefine or use Zone AE. Clarify the
elevation and freeboard requirements above
natural grade in approximate Zone A, with no BFE.
Refer to 44CFR Parts 59.1, 60.3(b) and (c).
NFPPR Combined comm rec and comments
Is a the rec and b the comment? Don’t see where b
is worded as rec—does it need to be? They seem
like two diff issues
Who? How? LL
Really like this one—it is specific as to who, what
and how
Should it be the first rec in this section? Since it
seems very overarching
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National Flood Policy—ASFPM 2015 Recommendations
M.4. FEMA should resume the needed arid regions
research that was started with the 1985 DMA
study and the 1996 National Academy study.
A starting point for resuming this effort may
include:
•
Review the effectiveness of present
identification, characterization, and mapping
guidelines in Appendix G. Identify pros and cons.
•
Collect alluvial fan flooding mitigation
efforts utililized in the arid regions. Establish postconstruction performance of these features.
Identify pros and cons.
•
Establish specific aspects of both Appendix
G guidelines and mitigations efforts which need
improvement and/or further research and
development.
•
In light of recent improvements in
modeling software, FEMA should resume the
alluvial fan flooding research that was started with
the 1985 DMA (“DMA” needs identification at first
instance?) study and the 1996 National Academy
study. This effort should establish clear guidance
and policy on the applicability of different
software on active and inactive alluvial fan
flooding areas, and establish different
classifications if necessary and appropriate.
•
Establish policy and guidance to ensure
that new technology used to determine flood
hazards is not improperly used to allow
development in areas where high risk alluvial fan
flooding is possible.
•
Coordinate with the Army Corps of
Engineers to develop guidance on the appropriate
application of two dimensional software (including
theirs) on alluvial fans and areas of unpredictable
flow paths. This would produce defensible
recommendations by an organization with no
conflicting interests in the determination.
NFPPR Combined comm rec and comments
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