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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 AG5000.072.kp 021294 \\A:Cf CORPUS CHRISTI 4ittliblED 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 066 atyy, 041?C .