| (a) RFPGs shall perform potential future condition
flood risk analyses for the region comprised of:
(1) flood hazard analyses that determines location,
magnitude and frequency of flooding;
(2) flood exposure analyses to identify who and what
might be harmed within the region; and
(3) vulnerability analyses to identify vulnerabilities
of communities and critical facilities.
(b) RFPGs shall perform a future condition flood hazard
analysis to determine, at a minimum, the location of 1% both annual
chance and 0.2% annual chance flood events as follows:
(1) collect best available data and conduct analyses
sufficient to characterize the future conditions for the planning
area based on a "no-action" scenario of approximately 30 years of
continued development and population growth under current development
trends and patterns, and existing flood regulations and policies.
RFPGs shall consider the following as available and pertinent in the
FPR:
(A) current land use and development trends and practices
and associated projected population based on the most recently adopted
State Water Plan decade and population nearest the next RFP adoption
date plus approximately 30 years or as provided for in guidance;
(B) reasonable assumptions regarding locations of residential
development and associated population growth;
(C) anticipated relative sea level change and subsidence
based on existing information;
(D) anticipated changes to the functionality of the
existing floodplain;
(E) anticipated sedimentation in flood control structures
and major geomorphic changes in riverine, playa, or coastal systems
based on existing information;
(F) assumed completion of major flood mitigation projects
currently under construction or that already have dedicated construction
funding; and
(G) other factors deemed relevant by the RFPG.
(2) identify areas within each FPR where future condition
hydrologic and hydraulic model results are already available and summarize
the information;
(3) utilize best available data, hydrologic and hydraulic
models for each area;
(4) where future condition results are not available,
but existing condition hydrologic and hydraulic model results are
already available, the RFPGs may modify hydraulic models or existing
condition flood hazard boundary to identify future conditions flood
risk for 1% and 0.2% annual chance storms based on simplified assumptions
in accordance with EA guidance.
(5) prepare a map showing areas of 1% and 0.2% annual
chance of inundation for future conditions, the areal extent of this
inundation, and the types of flooding for each area.
(6) prepare a map showing gaps in inundation boundary
mapping and identify known flood-prone areas based on location of
hydrologic features, historic flooding, and/ or local knowledge.
(c) The RFPGs shall use the information identified
in the potential future condition flood hazard analysis to develop
and perform future condition flood exposure analyses to identify who
and what might be harmed within the region for the potential future
condition 1% annual chance and future condition 0.2% annual chance
flood event. At the RFPGs’ discretion, the future condition
flood exposure analysis may include an analysis of existing and future
developments within the future condition floodplain and the associated
flood hazard exposure.
(d) Future condition vulnerability analysis.
(1) RFPGs shall identify resilience of communities
located in flood-prone areas identified in the future condition flood
exposure analysis utilizing relevant data and tools.
(2) RFPGs shall identify vulnerabilities of critical
facilities to flooding by looking at factors such as proximity to
a floodplain and other factors as included in the EA guidance.
(e) All data produced as part of the future condition
flood hazard analysis and future condition flood exposure analysis
shall be summarized in the RFP in accordance with guidance provided
by the EA and shall include:
(1) underlying flood event return frequency;
(2) type of flood risk;
(3) county;
(4) existing flood authority boundaries;
(5) social vulnerability indices for counties and census
tracts; and
(6) other categories to be designated by the EA.
(f) The information developed by the RFPG under this
section shall be used to assist the RFPG establish priorities in subsequent
planning tasks, to identify areas that need FMEs, and to efficiently
deploy its resources.
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