HomeMy WebLinkAbout021294 RES - 12/03/1991A RESOLUTION
ADOPTING A REPETITIVE LOSS PLAN, A COMPONENT OF THE COMMUNITY
RATING SYSTEM PROGRAM, IN ORDER TO MAINTAIN ELIGIBILITY FOR
DISCOUNST ON PREMIUMS FOR FLOOD INSURANCE IN THE CITY.
NOW, THEREFORE, BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY
OF CORPUS CHRISTI, TEXAS:
SECTION 1. That there is hereby adopted a Repetitive Loss Plan, a substantial
copy of which is attached as Exhibit "A."
A1'1'EST:
City Secretary MAYOR
THE CI
APPROVED: _4 DAY OF NOVEMBER, 1991
JAMES R. BRAY JR., CITY ATTORNEY
BY-Ati
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021294
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CORPUS CHRISTI
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CITY OF CORPUS CHRISTI
Repetitive Loss Plan
A. INTRODIJCTION AND PURPOSE
B. PROBLEM IDENTIFICATION
1. Topography
2. Soils
3. Flood History
4. Hurricanes
C. FLOOD HAZARD AREAS
1. Development Trends
2. Development Constraints
3. Critical Facilities
D. REPETITIVE LOSS AREA INVENTORY
1. Investigation Process
2. Specific Site Data
3. Summary of Inventory
E. SELECTION OF APPROPRIATE ACTIVITIES
1.. Short -Range Activities
2. Long -Range Activities
EXHIBIT A
INTRODUCTION AND PURPOSE
This document will serve as the City of Corpus Christi's Repetitive
Loss Plan. It has been prepared to reduce property damage/losses in
repetitive loss areas during flood conditions. Repetitive loss sites are
those which have claimed for insurance losses of $1,000 or more two or
more times. The plan addresses the sources of the problem and defines
activities for problem resolution. In addition, this plan will assist
State and Federal agencies in mitigation planning and funding efforts.
This Repetitive Loss Plan was coordinated by the Flood Plain
Administrator, who received input from the Planning Department, the
Engineering Service Department, the Storm Water Division, the Emergency
Management Department, and the Building Inspection Department. The plan
addresses the problems in the repetitive loss areas and outlines both
short and long range activities that will lead to the correction. of those
flooding problems. The repetitive loss areas are identified on the
Exhibit titled Repetitive Loss Areas. The plan's preparation, section
headings, and general strategy follow the guidelines and criteria set
forth in Section 241 of the Community Rating System Commentary.
PROBLEM IDENTIFICATION
Topography
The City of Corpus Christi can be found in the Southern half of
Texas along Corpus Christi and Nueces Bay, on the Gulf Coast, 10 miles
west of the Gulf of Mexico. A more precise description of its location
is 27 degrees, 45 minutes North Latitude and 97 degrees, 25 minutes West
Longitude. This crescent shaped City is 31 miles long and 15 miles wide
totalling 124.5 square miles in land area.
Due to its establishment along the coastal periphery of the Texas
Gulf Coast Plain, where the Nueces River discharges into Corpus Christi
and Nueces Ray, Corpus Christi's topography is a uniform grade that
slopes gently to the southeast. The highest elevation is approximately
85 feet above sea level, gradually decreasing to the Cayo De) Oso, Laguna
Madre and both bays.
Surface configuration; or topography, refers to such elements as
slope, elevation drainage, and surface materials. Each has a distant
variable in the physical development and land use trends of the City. As
a result of the City's vast, flat terrain, slope becomes one of the
principal elements of this surface configuration. it represents one of
several factors which determines the suitability of an area. The City's
flat terrain influences, more than any other environmental element, a
variety of activities ranging from structure location to transportation.
EXHIBIT A
Review of the data presented in the attached Topography Map reveals
the effect that topography has .Lr: Corpus Christi. The uniform
characteristic of the slope, which averages about 3.5 feet per mile, or
0.7%, becomes a major consideration. Few special conditions in land use
planning are given with regard to the topography. Although concern of
oversteep slopes is usually not a major constraint in this area, the lack
of graduation adversely affects most of the City with respect to
flooding. This lack of relief often has a "pooling effect" during
excessive rain fall in several areas of the city; typically undeveloped
areas are inundated due to a lack of run-off. As a result, emphasis
must be given to drainage design and facilities.
In addition, because of the City's level terrain storm drainage
systems utilize the minimum slope allowed. This in turn raises the
hydraulic gradient resulting in larger than normal pipe sizes, to
compensate for the lack of grade and the lack of flow velocity.
Historically, sufficient facilities have been constructed throughout the
City- However there are several sections of the City, in older
neighborhoods where open ditches and underground drainage structures are
marginally adequate to handle heavy rainfall. These areas tend to flood
during some heavy thunderstorms and during hurricane conditions because
of the i.imited existing capacity the system and present day population
development,
Soils
Without question soils constitute a significant aspect of the
physical environment. Knowledge and understanding of the complexity and
diversity of soil properties, as well as their chemistry, is essential in
determining the type of land uses and the type of structures that soils
can support. Permeability, soil reaction, salinity, shrink -swell
potential, risk corrosion, and texture, are major factors used in
determining the suitability of an area with reference to not only land
use and structural design, but also to the design and construction of the
drainage systems.
With 62% of the soils in Corpus Christi evolving from the clayey
materials of the Pleistocene Beaumont Formation, it is little wonder that
Corpus Christi has drainage problems. These properties are identified
with and are represented by the Victoria Association. Victoria clays,
known as the black land soils of the coastal plain, are characterized by
ahigh shrink -swell ratio and a high salinity content. The soils require
special consideration in preventing the cracking of building walls, of
foundations, of roads, and of underground utility services.
to addition to the predominant clays of the Victoria Association,
the other soils found in Corpus Christi and the surrounding communities
have varying degrees of sand, silt, and clay. These soils comprise the
remaining 38% of the association found in Corpus Christi and include such
soil series as Miguel--Willacy, Lomalta, Orelia-Banquete,
Trinity -Frio -Zavala and Galveston -Mustang. Unfortunately, the
characteristics identifled with these soils are not much better than
those associated with the Victoria series. They too present problems
'^;XHIMT A
related to surface and subsurface drainage, to a high water table, and to
a high salt and lime content.
Flood History
Most of the Repetitive loss claims were reported during a five year
period, from 1978 to 1983, and between the months of August and October,
of these years. The City of Corpus Christi experienced unusually heavy
rainfalls during that time, including a one month's rainfall totaling of
14.79". These rainfall totals were taken at the Corpus Christi
International Airport.
Analysis of supplemental data from the national weather service,
suggest that the unusually heavy rainfall that fell on Corpus Christi
during these particular years and months were related to stalled
extratropical low pressure systems or convective frontal systems. These
two types of systems generate high intense showers for consecutive days
resulting in flooding throughout the city. Further comparisons show that
of the 44 repetitive loss locations identified, in 42 of them, one or
more of the repetitive loss claims were related to flooding that
corresponded to those dates of unusually high rainfall totals, and 72% of
the claims indicated flooding as the primary cause for the claim.
Hurricanes
A climatic peril for any coastal city is the impact of a hurricane.
With hazards that include high winds, intense rains, storm surges, and
flooding, hurricanes are one of the primary reasons given for damage on
insurance claims. When one compares the dates of the last two
hurricanes, Allen, on August 10, 1980 and Gilbert, on September 16, 1988,
with the dates shown on the repetitive loss claims, it is not surprising
that these dates coincide with the dates of many of the claims reported.
The rainfall for Allen and Gilbert measured 10.35" and 6.30"
respectively, with wind gust .between 75 and 100 miles per hour.
Approximately 65% of the repetitive loss claims were directly related to
Hurricanes Allen and/or Gilbert,
F1,00D HAZARD AREAS
Development Trends
The City of Corpus Christi along with the South Texas Water
Authority, and Nueces County have contracted with a consulting
engineering firm to prepare a Regional Stormwater Master Plan for both
the City and County. In order to determine future drainage needs and to
properly design drainage structures, both underground and open ditches,
population and land use projections were needed. The City provided the
consulting engineer with population projections and land use development
trends. The report is identified as Appendix "A" and provides
supplemental data. Population and land use trends are an essential facet
EXHIBIT A
of a Comprehensive Plan. The City of Corpus Christi, in compliance with
the City Charter, which establishes the vehicle for guiding, regulating
and managing future development, is preparing such a document.
Development Constraints
The Comprehensive Plan consists of three elements: area development
plans; policy statements; and master services plans. It is, however, the
Area Development Plans (ADPS) that wil) propose policies pertaining to
land use, drainage, zoning transportation, environmental protection,
economic development, parks, and open space. Thus far, by resolution;
seven of thirteen ADP's have been completed and approved.
As a means of reducing the impact that development might have in or
adjacent to the 100 year flood plain, some ADP's have recommended that
overlay districts be imposed. The purpose of such an application is for
the protection of environmentally sensitive areas and for the control of
density and of the type of development permitted along drainage ways.
More detail on the proposed overlay district can be found in the Section
entitled, Selection of Appropriate Activities, of this report.
In addition to requiring compliance with the comprehensive plan, and
as a means of trying to further reduce repetitive losses, the City of
Corpus Christi may dictate other constraints. Three other methods of
imposing these additional limitations are the zoning ordinance, platting
ordinances and property acquisition. However, none are so restrictive
that the objection can be over come.
Three zoning districts have been established in Corpus Christi to
control density: 1. "FR" - Farm Rural (1 unit per 5 acres); 2. "RE" -
Residenti.al Estate (1 unit per acre): and 3. "RA" - Residential Acreage
(15,000 sq. ft. 3ot). At the present time, there are no provisions in
the zoning ordinance for a district requiring for land that is in a flood
zone to remain open. Nor are there any restrictions on development
within the floodplain except as provided by the National Flood Insurance
Program regulations. The zoning ordinance regulates density only.
Platting on the other hand. curbs development by requiring
construction drawings that show and conform to the drainage patterns and
structures dictated by the Master Drainage Plan. These drawings insure
proper drainage for the subdivision as well as for the surrounding area.
In an area where the development conflicts with the floodplain, more
detailed information is requested, Added contours are shown as well as
the boundaries of the floodplain. If no adverse effects are noted, or if
the flow of the drainage can be redirected without causing flooding
either in, around or up stream of the subdivision, the development may he
constructed.
Ownership is the third means of managing development. To preserve
the integrity of the flood hazardous areas, the City has obtained some
ownership of properties in these areas. The City has three processes in
which to gain property. First, the City can purchase the land. This
process would include condemnation. Second, the property owner might
donate the land. Finally: the City can secure land through the park
EXHIBIT A.
dedication requirement of the platting ordinance. The City has, and will
continue to encourage property developers to satisfy the development park
dedication requirement by setting aside land which is adjacent to
waterways. In many cases, the City finds that no one method fits every
situation. At time, one of any combination of these three methods may be
used for securing and controlling property in flood hazard areas.
Even though the City maintains ownership of several acres of real
estate in and adjacent to flood hazardous areas, one exception is the low
lying areas on North Beach (North Central ADP). There are several acres
of vacant property within this repetitive loss area that are still under
private ownership. However, due to its tourist potential, recreational
nature, and an effort to stimulate economic growth, the City has and is
encouraging redevelopment. The North Central ADP implies that
redevelopment focus on high-rise residential units, motels, hotels and
commercial activities. The plan denotes that new construction must meet
the base flood elevation established by City's floodplain regulations and
NFIP requirements.
Critical Facilities
The City's Emergency Management Division has provided the Critical
Facilities List presented in Appendix B. Of the facilities mentioned,
four are located in the repetitive loss area of North Beach. The Texas
State Aquarium has been built according to NFIP Criteria. The evacuation
routes of State Highway 181 and the Nueces Bay Causeway have been
improved and elevated to avoid flooding. The remaining two facilities
are HITOX Company, located in Rincon Industrial Park and a gas regulator,
along the ship channel, belonging to the City of Corpus Christi. Prior
to 1983 HITOX Company was outside the corporate limits of the City and
did not fall under the City's Flood Hazard Prevention Ordinance. After
it's annexation in 1983 HITOX Company has adhered to NFIP criteria for
construction work performed on that facility. The gas regulators are
protected by placing the control valve on high ground such that the gas
may be turned off during flooding conditions.
REPETITIVE LOSS AREA INVENTORY
Investigative Process
Based on the dates of repetitive Joss claims and on the improvements
that have been performed since those claims, some of the Repetitive Loss
Areas have already been addressed, some can be addressed, and others may
have to be addressed indirectly. An investigation of all the repetitive
loss locations revealed that the sources of the problem ranged from what
appeared to be an inadequate drainage design to the need for the property
owner to address drainage problems within private property.
The type of investigations that occurred consisted of visual
inspections of the sites, a general. study of the drainage maps, and an
overview of the projects that have been performed in the areas to
alleviate the flooding conditions. Detailed calculations of watershed
areas and drainage ditches or storm water pipes sizing were not made for
EXHIBIT A
this study. The repetitive loss areas were identified by number, and
when applicable, were grouped into clusters which could he addressed
simultaneously. For the purpose of anonymity, the locations were
identified by names and numbers instead of address.
Specific Site Data
CALALLEN - #26
This site is located at the bottom of rolling terrain at the
intersection of curb and guttered streets. The storm water system
has been improved and additional improvements to the catch basins
were set in place since the claims were filed to alleviate the
problem. Indications are that the improvements that have occurred
have provided relief from flooding to this area.
LEOPARD - #27
This site is located at the edge of a neighborhood with developed
curb and guttered streets. By the entrance of the subdivision,
there is a set of catch basins which collect water from drainage
ditches that run along a paved undeveloped street. The undeveloped
street is a long street which is elevated higher than the developed
neighborhood and has drainage ditches along both sides. By the
entrance of the .subdivision, there is a set of double culvert pipes
draining one of the ditches into the ditch beside the site. It
appears that the catch basins are not capable of accepting the
additional flow. The catch basins drain the water to a storm sewer
system that is located across the street. The storm sewer system is
designed to accept drainage from the developed subdivision.
The apparent solution to this problem is to delete the set of double
culvert pipes, and to install an adequately sized pipe which would
drain the water from the ditch directly into the storm sewer which
is located below it. Additional study will have to be performed to
verity watershed areas, pipe sizing, and storm sewer sizing.
LEOPARD - #25 and #28
These sites are located i_n rolling terrain which has a natural
drainage ditch winding through it. Part of the ditch has a
permanent concrete lining and a portion of it does not. This ditch
is located at the rear of the sites. The catch basin that drains
the street and the ditch appears to be adequately sized. At the
request of the citizens in the area, a grate was installed behind
the opening of the catch basin to keep children from playing inside.
During a storm or heavy rains, debris could restrict the flow into
the catch basin, causing the water to back up behind it.
It appears that a solution to the problem could be to remove the
grate at the rear entrance of the catch basin, allowing unrestricted
flow of the storm sewer system. Long term projects could include
concrete lining the portion of the ditch that has not been lined and
EXHIBIT A
installing a structure with a slanted grate which would prevent debris
from building up against it. Additional study should be done to verify
watershed area drainage and storm sewer sizing.
LEOPARD - #24
The site is located along a paved, unimproved street which drains
the water through open ditches, to culvert pipes, and then drains
across the road into a natural drainage area. The Natural drainage
area is overgrown with vegetation, and debris has been dumped into
it, hampering the drainage capacity of the area. Also, agricultural
fields on either side of the natural drainage area add silt into
this natural drainage area which eventually becomes Till Creek.
It appears that clearing and grading the natural drainage area and
properly sizing the culvert pipe which crosses the street would
provide flood relief. Presently, the State regulates natural
drainage areas. Easement acquisitions would have to be made to
maintain proper drainage. Additional study would have to be
performed to determine the watershed area drainage and to properly
design the ditch and culvert pipes.
LEOPARD - #23
This site is located along a paved, unimproved street which drains
the water through open ditches into what appears to be an
inadequately sized open drainage ditch that is located between
commercial property and residential dwellings on a 20 foot drainage
easement. It appears that the installation of approximately 1000
feet of adequately sized storm sewer pipe would provide flood relief
to this area. Additional detailed studies would have to be
performed to calculate the watershed area and the storm sewer pipe
size.
LEOPARD - #20 and #43
This site is located in an area that is very close to a collector
drainage ditch. These sites drains into the ditch through an 18
inch culvert pipe. It appears that the 18 -inch pipe size is
adequate to drain the repetitive loss area.
The problem appears to be the backing -up of water from the collector
ditch, due to the restricted flow from growth of the vegetation
obstructing the water flow. The problem appears to exist on the
natural drainage portion of the ditch which is State controlled
property. An easement acquisition would have to be obtained in
order to maintain the portion of the ditch which appears to be
causing the water to back up.
LEOPARD - #22
This site is located along a paved, unimproved street which has open
ditches along both sides of the street. It appears that the cause
of the problem could be the hacking up of water due to improper
EXHIBIT A
ditch sizing and/or the need to clean and grade the ditches. A detailed
study of the area would be required to verify watershed area drainage and
culvert pipe sizing. Also, the cleaning and grading of culverts could
provide some flood relief for this area.
UP RIVER - #18
This site is located by a paved, unimproved road with open ditches
on either side of the street. The ditches drain in one direction on
one side of the street and back in the other direction to a culvert
box on the other side of the street and back in the other direction
to a culvert box on the other side of the street. The culvert box
structure then drains into a large, concrete -lined, collector ditch
which flows through refinery property and into the Nueces Bay.
It was very difficult to ascertain the cause of the flooding problem
due to the lack of damage data. The culverts in this area appear to
be restricted with silt accumulation. Cleaning and grading of
culverts and ditches could provide flood relief. Additional
detailed studies would have to be done to calculate the watershed
area and the ditch and culvert pipe sizing.
LEOPARD - #21
This site is located along a paved, unimproved street which has open
ditches along both sides of the street. The section of the street
near the site has a storm sewer pipe that drains one of these
ditches. This site is drained through grates, which have access to
the storm sewer pipe. Many of the grates are small and can become
ineffective if debris should block grate drainage.
It appears that the replacement of these grates with catch basins
and the cleaning and regrading of the drainage ditches would provide
relief to the area. Additional study should be done to verify that
the existing system can handle the watershed drainage area.
LEOPARD - #3 and #19
This site is located along a paved, unimproved street that has
ditches along both sides of the street. The culvert pipes in the
area appear to be undersized and the ditches and culvert pipes
appear to need maintenance. Cleaning and regrading of ditches along
with proper sizing of culvert pipes should provide flood relief to
this area. Additional detail studies should be conducted to verify
the watershed area drainage and to verify culvert and ditch sizing.
NORTH BEACH - #11, #12, #13, #14, #15, #16, AND #44
These sites are located in an area identified as a Special Flood
Hazard Area. All of the buildings on the sites were built at ground
level and are subject to flooding during storm surge conditions.
The building on #44 has been removed, and the property is vacant and
subject to current floodplain management regulations.
EXHIBIT A
ARCHDALE - #35
This site is in a residential area which is next to an open
agricultural field. The agricultural field drains naturally toward
the residential area. It appears that the water drains across the
field, behind several residential dwellings, and then between two
residential dwellings. It appears that flooding occurs to one
residence as it cuts between the structures.
This drainage is all occurring on private property. Future
development of the agricultural field could redirect drainage of the
field into a storm sewer system, reducing the flow. Before
improvements are made to the adjacent fields, the property owners
should take steps to safely direct the water between the two
residences to provide flood relief from this condition.
HOLLY - #33
This site is located at an intersection of two streets, along a
paved, improved street with a major drainage ditch running along the
opposite side of the street. A catch basin system, located by the
property, acts as a major collector of water from that neighborhood.
The catch basin system appears to be properly sized to drain the
neighborhood, but there is also a ditch along Holly Road that drains
into this system causing an apparent system overload.
Presently, there are plans to improve Holly Road, which would
include the drainage system. Improvements by the Texas Highway
Department are scheduled to start within 4 years.
HOLLY - #29
This site is located in an area that has been improved since the
claims were made. Improvements that have been made in this area
have provided the flood relief that is needed for this area.
HOLLY - #34
This site is located by a paved unimproved street which has drainage
ditches running along both sides of the street. It appears that
cleaning and grading of the ditch that is in front of the property
would provide the needed flood relief for this area. A detailed
study should be conducted to compare ditch and culvert pipe capacity
with the watershed area for adequate drainage.
MCARDLE - #11.
This site is located very close to a Special Flood Hazard Area.
From visualinspection, and without damage data, the reason for
flooding cannot readily be determined. Drainage of the area appears
to be adequate. The reason for flooding appears to be a pond,
located on private property, that may have had drainage problems.
The claims that were reported were reported over 10 years ago. It
appears that any design deficiencies of the pond may have been
EXHIBIT A
Leopard - #3 and #19: Cleaning and grading of ditches and
resizing culvert pipes could provide flood relief.
North Beach - #11, #12, #13, #14, #15, #16, and #44: Modifying
the Floodplain Ordinance would address future
construction in this area. Existing non -conforming
construction would have to be addressed with the
floodplain regulations that are now in place.
Downtown - #4, #5, #8, #9, and #10: Improvements have been
made to provide flood relief.
Staples - #6 and #7: Improvements have been made to provide
flood relief.
Ocean Drive - #17: Improvements have been made to provide flood
relief.
Hayward - #30 and #32: improvements have been made to provide
flood relief..
Ocean Drive - #31: Property Owners could make modifications to
their internal drainage system to provide flood
relief.
Archdale - #35: Property Owners could make modifications to
the drainage system to provide flood relief.
Holly - #33: Improvements to Holly Road, which are
scheduled to start within 4 years, should provide
flood relief.
McArdle
- #1: Property owners could make modifications to the
drainage system of their pond to correct the
flooding conditions.
Holly - #34: Cleaning and grading of ditches in this area
should provide the flood relief needed.
Laguna Shores - #2, #36, #37.. #38, #39, #40, #41, and #42:
Modifying the Floodplain Ordinance would address
future construction in this area. Existing
non -conforming construction would have to be
addressed with current floodplain management
regulations.
As mentioned in the Repetitive Loss Area Inventory, Investigation
Process, some of these locations have already been addressed. Some can
be addressed, and other areas may not be addressed directly.
Twelve (12) areas have undergone capita] improvements after the claims
were made:
1. Calal]en #26
2. Staples #6 and #7
3. Downtown #4, #5, #8. #9. and #10
4. Ocean Drive #17
EXHIBIT A
5. Hayward #30 and #32
6. Holly #29
Three (3) locations require corrections which would have to be performed
by property owners within private property include:
1. Ocean Drive #31
2. Archdale #35
3. McArdle #1
Fifteen (15) locations would require increased floodplain regulations
which would indirectly provide flood relief after a period of time:
1. North Beach #11, #12, #13, #14, #15, #16, and #44
2. Laguna Shores #2, #36, #37, #38, #39, #40, #41, and #42
One (1) location in which the City would be working in cooperation with
the Texas Highway Department is:
1. Holly #33
Of the 44 Repetitive Loss sites, there are thirteen (13) locations which
can further be addressed by the City. These locations are grouped in the
following sections under Short -Range Activities and Long -Range
Activities.
SELECTION OF APPROPRIATE ACTIVITIES
Short -Range Activities - Monies have been allocated in the 1991-1992
Budget to address six (6) Repetitive Loss Sites:
I. Analyze the drainage system for Leopard #27, and provide the
necessary modifications to the drainage system to provide flood
relief for this area.
2 & t. Analyze the drainage system for Leopard #25 and #28, and provide
the necessary modifications to the drainage system to provide
flood relief to this area.
4 & 5. Analyze the drainage system for Leopard #3 and #19, and the clean
and grade the ditch and culvert pipes to provide flood relief.
6. Analyze the drainage system for Holly #34, and clean and grade
the ditches and culvert pipes to provide flood relief.
Long -Range Activities - A feasibility study will have to be done on the
following projects, and the necessary budget allocations will have to be
performed within five (5) years to implement the following activities:
1. Analyze the drainage system for Leopard #22, and the clean and
grade the ditches and culvert pipes to provide flood relief.
EXHIBIT A
Corpus Christi, Texas
day of NQ a/11 K1SLh , 19 q
The above resolution was passed by the following vote:
Mary Rhodes
Cezar Galindo
Leo Guerrero
Betty Jean Longoria
Edward A. Martin
Joe McComb
Dr. David McNichols
Clif Moss
Mary Pat Slavik
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