FY2015 Flood Risk Assessment and
Risk Reduction Plan Implementation
May, 2014
Table of Contents
1.
Purpose........................................................................................................................ 1
2.
FY2015 Updates to the RA/RR Plan .......................................................................... 1
3.
FY2015 Scores ............................................................................................................ 3
4.
FY2015 Prioritization ................................................................................................. 6
a.
Category 1: Grant Eligible Properties ..................................................................... 6
b.
Category 2: Locally Funded Acquisitions .............................................................. 7
c.
Category 3: Real Estate Studies .............................................................................. 7
d.
Category 4: Other .................................................................................................... 8
5.
References Cited ......................................................................................................... 9
6.
Appendices ................................................................................................................ 10
Appendix A ............................................................................................................... 10
Appendix B ............................................................................................................... 12
Appendix C ............................................................................................................... 15
Appendix D ............................................................................................................... 19
List of Figures
Figure 1:
Figure 2:
Figure 3:
Figure 4:
Location of PMR 1 and PMR 2 (FY2015 Study Areas) .................................... 2
Breakdown of FY2015 Scores ........................................................................... 4
Distribution of FY2015 Scores........................................................................... 4
Geographic Distribution of FY2015 Scores ....................................................... 5
List of Tables
Table 1: Test 1 Questions .................................................................................................. 6
Table 2: Test 2 Questions .................................................................................................. 6
Table 3: Test 3 Questions .................................................................................................. 7
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
1. Purpose
The purpose of this document is to present the Fiscal Year 2015 (FY2015)
implementation of the Flood Risk Assessment and Risk Reduction Plan (RA/RR Plan)
(CMSWS, 2012). The RA/RR Plan was presented by Charlotte-Mecklenburg Storm
Water Services (CMSWS) staff, endorsed by the Storm Water Advisory Committee and
subsequently approved by the Mecklenburg County Board of County Commissioners in
2012. FY2015 will be the second year of implementation of the RA/RR Plan. The
RA/RR Plan is intended to be a dynamic, continuously updated plan that will aid in
identifying, prioritizing and planning flood mitigation projects. The RA/RR Plan
includes three main elements which link Flood Risk Property Scores at the individual
property level with Risk Reduction Recommendations that are then supported by Flood
Mitigation Priority Scores. Each element builds upon the previous element to produce
the results that will be assigned to the property as follows:



Flood Risk Property Score—consists of analyzing factors related to flood
impacts, storm frequency, and structure location on an individual property basis.
Risk Reduction Recommendations—consists of evaluating 19 different flood
mitigation techniques deemed most appropriate for Mecklenburg County and
making a planning-level recommendation of either 1) Highly Effective,
Recommended, 2) Effective, 3) Further Evaluation Needed, or 4) Not
Recommended.
Flood Mitigation Priority Scores—consists of assessing and accounting for
community benefits and other factors based on Risk Reduction Recommendations
that are not accounted for in the Flood Risk Property Score. The Flood Mitigation
Priority Score is used to prioritize individual properties as well as project areas
(i.e., groups, or “clusters” of properties) for mitigation activities.
2. FY2015 Updates to the RA/RR Plan
Many of the datasets used to calculate the elements described above for FY2015 were
updated from FY2014. Each updated dataset is as follows:

Flood Rasters and Flood Polygons—the most up-to-date flood rasters and flood
polygons were utilized for the FY2015 RA/RR Plan. The complete datasets were
only available for PMR 1 and PMR 2 (see Figure 1), therefore only properties
within these areas were considered for implementation during FY2015.
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
1
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Figure 1: Location of PMR 1 and PMR 2 (FY2015 Study Areas)




Past Mitigation—all past mitigation efforts (including those completed before
April, 2014) were included in the analysis.
Environmental Focus Areas—dataset was updated using input from the Storm
Water - Water Quality Program.
Greenways—updated Tier 1 Greenway Projects (expected to be constructed in the
next 5 years) were considered in the analysis.
Parks—updated existing and future locations for Park and Recreation Facilities
were considered in the analysis.
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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

Sewer Projects—updated Charlotte Mecklenburg Utility Department Capital
Improvement Plan (CIP) data (projects expected to be constructed in the next 5
years) were used for the FY2015 analysis.
Water Quality Capital Improvement Project Sites—updated locations of Storm
Water - Water Quality Capital Projects expected to be constructed in the next 5
years were included.
3. FY2015 Scores
In order to prioritize mitigation projects for FY2015 the Risk Assessment Risk Reduction
Tool (RARRT) was updated with the datasets described in the previous section and new
simulations performed. Simulations were completed for every active elevation certificate
within the PRM 1 and PMR 2 study areas (Figure 1). A total of 5204 elevation
certificates were analyzed and assigned scores. The scores ranged from a low of 0 (very
low priority) to a high of 3832 (very high priority). In order to visually identify scores
for individual properties the following color palette is used throughout this document:



Highest Priority Properties—Flood Mitigation Priority Scores of 1000 or more
are colored red. Typically these properties exhibit flood elevations greater than
finished floor elevations in more frequent events (such as the 10 year event).
Moderate Priority Properties—Flood Mitigation Priority Scores between 500 and
1000 are colored yellow. Moderate priority generally indicates finished floor
flooding during less frequent events (100 year), limited access during more
frequent events and location in previous project areas.
Lower Priority Properties—Flood Mitigation Priority Scores less than 500 are
colored green. These scores could indicate conditions ranging from no impacts
from the analyzed events (score of 0) to yard flooding or more substantial
impacts.
The grouping of the scores into the 3 previous categories for all 5204 elevation
certificates analyzed is presented in Figure 2.
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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<500 (4937 ECs)
500 - 999.99 (178 ECs)
>1000 (89 ECs)
Figure 2: Breakdown of FY2015 Scores
Figure 3 presents the distribution of all 5204 elevation certificates analyzed.
FY2015 RARRT Final Score Distribution
1400
5204 Active EC's Analyzed
2014 Active EC's
Moderate Priority
1200
1202
High Priority
Final RARRT Score
1000
800
600
526
400
261
200
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0.7
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0.9
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Percentile
Figure 3: Distribution of FY2015 Scores
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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Figure 4 presents the geographic distribution of the FY2015 scores by six square mile
sub-basin. Note that the color indicates the overall flood mitigation score (red indicates
generally higher scores relative to other basins) and does not directly correlate to high,
moderate and low priority basins. The labels indicate the total number of elevation
certificates analyzed in the basin for FY2015.
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Figure 4: Geographic Distribution of FY2015 Scores
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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As expected, the older and more built-up areas of Mecklenburg County tend to have the
highest Flood Mitigation Scores. Most of these basins are located within the City of
Charlotte. It is important to note that these areas were largely developed prior to the
adoption of flood plain ordinances. Conversely, areas that developed after the adoption
of the ordinances tend to exhibit lower scores, such as Huntersville, Cornelius, Matthews
and Mint Hill. This geographic distribution of scores is an indication of the effectiveness
of our local flood plain ordinances.
4. FY2015 Prioritization
The FY2015 prioritization is focused upon properties with high and moderate Flood
Mitigation Priority Scores. Each of these properties with a score of 500 or more was
placed into one of four categories depending upon several factors not considered in the
RARRT. The four categories along with an associated description are as follows:
a. Category 1: Grant Eligible Properties—FEMA has announced Hazard
Mitigation Assistance (HMA) funding for properties that are categorized as
Severe Repetitive Loss (SRL). Essentially these are properties that carry flood
insurance, have had 4 or more claims on their flood insurance policy and are
deemed beneficial to acquire or elevate. All properties that are categorized as
SRL and have an acquisition cost of $280,000 or less are deemed beneficial.
Similarly, properties that are SRL and have a cost to elevate of $140,000 or less
are deemed beneficial. If the cost to implement either of these techniques exceeds
the designated limit, a cost:benefit calculation can be performed to determine
grant eligibility.
The 42 properties identified as SRL were evaluated using 3 tests to determine
their ultimate suitability for inclusion in an HMA Grant. The tests are as follow:
Table 1: Test 1 Questions
Q1
Q2
Q3
Is the property located on the minor
system?
Is RARRT recommendation on acquisition
either effective or highly effective?
Is the property a part of a larger multifamily development?
If yes, property is excluded.
If no, property is excluded
If yes, property is excluded (based
upon complexity)
Table 2: Test 2 Questions
Q1
Is the cost for acquisition more than
$500,000
If yes, property is excluded (cost
benefit ratio is not favorable).
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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Table 3: Test 3 Questions
Q1
Is the cost to mitigate high compared with
the RARRT score
A value of >500 on this metric is
excluded. These properties tend to
be very expensive for the risk
mitigated.
Of the 42 SRL properties in Mecklenburg County, 4 passed the 3 suitability tests
and will be further evaluated for inclusion in an HMA grant. A listing of each
property and the data used to answer the 3 test is included with this document as
Appendix A. Note that HMA funding covers 100% of the cost of acquisition up
to $280,000 and 100% of the cost of elevation up to $140,000.
b. Category 2: Locally Funded Acquisitions—Properties with Flood
Mitigation Priority scores of more than 500 were considered for this category.
When appropriate, properties were grouped into project areas. Project areas were
then prioritized based upon Flood Mitigation Priority Score (higher score equated
to a higher rank). For multiple properties within a project area the highest scoring
property within the project area was used to rank the project area. Occasionally,
properties with a Flood Mitigation Priority Score of less than 500 were included
in a project area if the property met the following criteria:



Property was a part of a previous unsuccessful mitigation effort.
Surrounding acquisitions would have left property as a „patchwork‟ of unmitigated properties
Property is critical to a future CIP project
A total of 55 properties in 19 different project areas were included in this
category. CMSWS anticipates a total budget of approximately $5,000,000 will be
allocated to fund acquisition. In total the 55 properties will cost approximately
$9,200,000 to acquire and mitigate. Past experience indicates that some property
owners will not wish to participate. Additionally, other properties will be
excluded for various reasons. If these issues are encountered, the next property or
project area on the list will be included to take the place of the excluded property.
Properties identified in Category 2 are included as Appendix B.
c. Category 3: Real Estate Studies—properties assigned to the study category
can be grouped into one of the following sub-categories:

Complicated real estate situations involving very valuable commercial
property. Several commercial properties with Flood Mitigation Priority
Scores in excess of 1000 were identified in this sub-category. It is likely
that acquisition of these properties would take place over several years.
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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



Complicated real estate situations involving multiple buildings on a single
parcel where some are in the flood zone and some are not. These
properties will require sub-division and have proven to be very
challenging acquisitions in the past.
Properties protected by un-regulated levees. Several un-regulated levees
exist in Mecklenburg County. These situations will be evaluated to
determine their suitability for bringing into compliance
Properties that could be protected by new levees.
Properties with probable elevation certificate errors that require field
verification.
Properties identified in Category 3 were grouped into project areas and project
areas were prioritized based upon the highest scoring component. Studies will
be completed for the top 5 projects during FY 2015. All Category 3
properties are presented in Appendix C.
d. Category 4: Other—properties that have Flood Mitigation Priority Scores
greater than 500 and did not fit into the other categories. The unifying
characteristic of these properties is no action is recommended to be initiated
during FY2015. These properties tended to be grouped into the following subcategories:




Mitigation is currently underway though inclusion with earlier grants,
demolition permits or a permit to elevate. These properties will be
compliant with floodplain ordinances after mitigation is complete.
Non-participants. The owners of these properties have been approached
about participation in the Storm Water - Flood Mitigation program but
have declined. These properties will be periodically re-evaluated for
inclusion.
Contaminated properties. Several commercial properties with high Flood
Mitigation Priority Scores have known environmental contamination
issues. These properties will not be acquired with local or FEMA funds.
Self mitigation. Several areas of the county are experiencing rapid redevelopment of single family residential property. Typically, these
properties have land values that greatly outweigh the building values. In
these areas, investors are often acquiring homes located in a flood zone
and either tearing them down and rebuilding or are elevating them. In
either case, the result is a structure that is compliant with floodplain
ordinances. Properties in these areas will be monitored in the coming
years for self mitigation and inclusion in the acquisition category.
Properties assigned to Category 4 are presented in Appendix D. There are 108
properties in Category 4. As mentioned above, the RA/RR Plan is dynamic
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
8
and properties in Category 4 will change as current mitigation efforts are
implemented or not due to non-participating property owners.
5. References Cited
Charlotte-Mecklenburg Storm Water Services, 2012. Flood Risk Assessment and Risk
Reduction Plan, January, 2012.
FY2015 Flood Risk Assessment and Risk Reduction Plan Implementation
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