Current through Reg. 49, No. 52; December 27, 2024
(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.
