Federal Emergency Management Agency

Transcription

1 ORANGE COUNTY, TEXAS AND INCORPORATED AREAS COMMUNITY NAME BRIDGE CITY, CITY OF ORANGE, CITY OF ORANGE COUNTY UNINCORPORATED AREAS PINE FOREST, CITY OF PINEHURST, CITY OF ROSE CITY, CITY OF VIDOR, CITY OF WEST ORANGE, CITY OF COMMUNITY NUMBER Effective, Federal Emergency Management Agency Flood Insurance Study Number 48361CV000A i

2 NOTICE TO FLOOD INSURANCE STUDY USERS Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study may not contain all data available within the repository. It is advisable to contact the community repository for any additional data. Selected Flood Insurance Rate Map panels for the community contain information that was previously shown separately on the corresponding Flood Boundary and Floodway Map panels (e.g., floodways, cross-sections). In addition, former flood hazard zone designations have been changed as follows: Old Zone A1 through A30 V1 through V30 B C New Zone AE VE X X This preliminary revised Flood Insurance Study contains profiles presented at a reduced scale to minimize reproduction costs. All profiles will be included and printed at full scale in the final published report. Part or all of this Flood Insurance Study (FIS) may be revised and republished at any time. In addition, part of this Flood Insurance Study may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the Flood Insurance Study. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current Flood Insurance Study components. Initial countywide FIS effective date: ii

3 TABLE OF CONTENTS 1.0 INTRODUCTION... 1 Page 1.1 Purpose of Study Authority and Acknowledgments Coordination AREA STUDIED Scope of Study Community Description Principal Flood Problems Flood Protection Measures ENGINEERING METHODS Hydrologic Analyses Hydraulic Analyses Coastal Analyses Storm Surge Analysis and Modeling Statistical Analysis Stillwater Elevations Wave Height Analysis Vertical Datum FLOODPLAIN MANAGEMENT APPLICATIONS Floodplain Boundaries Floodways Base Flood Elevations Velocity Zones INSURANCE APPLICATIONS FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES iii

4 TABLE OF CONTENTS (Cont d) FIGURES Figure 1 Transect Schematic Figure 2 Transect Location Map Figure 3 Floodway Schematic TABLES Table 1 Scope of Previous Studies... 3 Table 2 Stream Name Changes... 4 Table 3 Summary of Discharges Table 4 Coastal Data Table Table 5 Floodway Data Table 6 Community Map History Page Exhibit 1 Flood Profiles EXHIBITS Adams Bayou Panels 01P-03P Anderson Gully Panels 04P-05P Caney Creek Panel 06P Coon Bayou Panel 07P Coopers Gully Panel 08P Cow Bayou Panels 09P-10P Cow Bayou Lateral No. 14 Panel 11P Gum Gully Panel 12P Hudson Gully Panel 13P Little Cypress Bayou Panel 14P Little Cypress Bayou Tributary Panel 15P Meyers Bayou Panel 16P Neches River Panels 17P-18P Sabine River Panels 19P-20P Sandy Creek Panel 21P Ten Mile Creek Panel 22P Ten Mile Creek West Fork Panel 23P Tiger Creek Panel 24P Walnut Run Creek Panel 25P Exhibit 2 Flood Insurance Rate Map Index Flood Insurance Rate Maps Exhibit Percent Annual Chance Wave Envelope - Transect Profiles iv

5 1.0 INTRODUCTION FLOOD INSURANCE STUDY ORANGE COUNTY, TEXAS [AND INCORPORATED AREAS] 1.1 Purpose of Study This Flood Insurance Study (FIS) revises and updates information on the existence and severity of flood hazards in the geographic area of Orange County, Texas, including the Cities of Bridge City, Orange, Pine Forest, Pinehurst, Rose City, Vidor, and West Orange; and the unincorporated areas of Orange County (referred to collectively herein as Orange County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of This study has developed flood-risk data for various areas of the community that will be used to establish actuarial flood insurance rates and to assist the community in its efforts to promote sound floodplain management. Minimum floodplain management requirements for participation in the National Flood Insurance Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR, In some States or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than the minimum Federal requirements. In such cases, the more restrictive criteria take precedence, and the State (or other jurisdictional agency) will be able to explain them. 1.2 Authority and Acknowledgments The sources of authority for this FIS report are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of The initial hydrologic and hydraulic analyses for the original studies in Orange County were performed by Tetra Tech, Inc. for the Federal Emergency Management Agency (FEMA), under Contract No. H This study was completed in June Updated hydrologic and hydraulic analyses for Cow Bayou were performed by Dodson and Associates, Inc., for the Orange County Drainage District. This study was completed in December The Comprehensive Flood Risk Resources & Response Joint Venture (CF3R) completed the base mapping activities and floodplain mapping (redelineating using effective flood profiles and updated topographic data) in accordance with Task Order 29, Task 40 for Orange County, Texas under Contract No. EMT-2002-CO The topographic data consist of countywide LiDAR data collected and processed by Sanborn from Colorado Springs, Colorado from June 2006 to April Michael Baker Jr., Inc. (Baker), a member of CF3R Joint Venture, managed the LiDAR data acquisition and processing effort. The Texas Coastal LiDAR Campaign Final Report for Orange County was completed in April Several sources were used for the base map data in this study. USGS Quadrangle information, obtained from the US Geological Survey was used primarily in the development of the FIRM Panel index layout. This data was obtained in November of 2007 with an unknown publication date. The original geographic coordinate system, North American Datum NAD 83, was converted to state plane Texas Central Zone Permanent 1

6 benchmark data was obtained from NOAA, National Geodetic Survey in October of 2007 with a publication date of North American Datum NAD 83 was the original geographic coordinate system converted to state plane Texas Central Zone 4203, using NGVD 88 vertical datum. All other base map data was provided by the Orange County Drainage District to be used in the study. The data was delivered in ArcGIS shapefile format in July 2008 and included transportation, surface water features (rivers, bayous, lakes, ponds), structures and political boundary areas projected in state plane Texas Central Zone All base map data was at a scale of 1:257,687, and all data was converted, if not already in, to state plane Texas Central Zone 4203 with NGVD 88 vertical datum. The storm surge analyses for this study were performed by the U.S. Army Corps of Engineers (USACE), for FEMA. This study was completed in November Coordination 2.0 AREA STUDIED The following organizations were contacted for coordination in the development of the original Orange County studies: City of Bridge City, City of Orange, City of Pine Forest, City of Pinehurst, City of Vidor, City of West Orange, Orange County, National Oceanic and Atmospheric Administration, Orange Chamber of Commerce, C.P. Smith Associates, Inc., Southeast Texas Regional Planning Commission, Texas Highway Department, Texas State Department of Community Affairs, Texas State Department of Highways and Public Transportation, Texas Department of Water Resources, U.S. Army Corps of Engineers, Galveston District, U.S. Geological Survey, and the U.S. Natural Resource Conservation Service. The State Coordinator was involved with this study through the Denton Regional office of FEMA. The results of the initial study were reviewed at a final coordination meeting in Orange, Texas on February 11, For this initial countywide FIS, the initial Consultation Coordination Officer (CCO) meeting was held on March 16, 2006, and attended by representatives of FEMA, CF3R Joint Venture, and community representatives. The results of this study were reviewed at the final CCO meeting held on, and attended by representatives of. All problems raised at that meeting have been addressed in this study. 2.1 Scope of Study This FIS report covers the geographic area of Orange County, Texas, including the incorporated communities listed in Section 1.1. The areas studied by detailed methods in the previously developed FISs were selected with priority given to all known flood hazards and areas of projected development or proposed construction. No new areas, except the coastal area, were studied by detailed methods during the preparation of this countywide FIS. Redelineation of effective floodplain boundaries (Zone AE) were performed by using the updated topographic data developed as part of Terrain Data Development for the Digital Flood Insurance Rate Map (DFIRM) Update Project for Orange County, Texas. 2

7 Table 1, Scope of Previous Studies, documents the limits of study for those streams studied by detailed methods in previous FISs. TABLE 1 SCOPE OF PREVIOUS STUDIES Stream Limits of Detailed Study Adams Bayou 8.6 miles from a point approximately 8,280 feet upstream of F.M to Dupont Drive Anderson Gully From Interstate Highway 10 to Southern Pacific Railroad Caney Creek From a point approximately 2,717 feet upstream of North Tram Road to its confluence with Tiger Creek Coon Bayou From a point approximately 2,680 feet upstream of East Hoo Hoo Road to its confluence with Cow Bayou Coopers Gully From 10 th Street to the Pier Road Pump Station in the City of Orange Cow Bayou From a point approximately 1,175 feet upstream of the confluence of Cow Bayou Lateral No. 14 to a point approximately 200 feet downstream of East Round Bunch Road Cow Bayou Lateral No. 14 From a point approximately 150 feet downstream of Interstate Highway 10 to its confluence with Cow Bayou Gum Gully From a point approximately 5,300 feet upstream of Alley Payne Road to F.M Hudson Gully From a point approximately 900 feet upstream of 37 th Street in the City of Orange to its confluence with Adams Bayou Little Cypress Bayou From a point approximately 12,500 feet upstream of the confluence of Little Cypress Bayou Tributary to its confluence with the Sabine River Little Cypress Bayou Tributary Approximately 1.7 miles downstream to its confluence with Little Cypress Bayou Meyers Bayou From F.M. 105 to Old Spanish Trail Neches River From the Orange-Jasper County boundary downstream to the Kansas City Southern Railroad Sabine River From the Orange-Newton County boundary downstream to the southern corporate boundary of the City of Orange Sandy Creek From a point approximately 80 feet upstream of Burton Drive to its confluence with Cow Bayou Ten Mile Creek From a point approximately 8,000 feet upstream of F.M to a point approximately 5,400 fee downstream of Lake View Road Ten Mile Creek West Fork From a point approximately 2,000 feet upstream of F.M to its confluence with Ten Mile Creek Tiger Creek From a point approximately 8,300 feet upstream of F.M. 105 to a point approximately 3,200 feet downstream of the Caney Creek confluence Walnut Run Creek From a point approximately 2,200 feet upstream of Isaac Street to F.M

8 All or portions of the remaining significant creeks and tributaries in the county were studied by approximate methods. Approximate analyses were used to study those areas having a low development potential or minimal flood hazards. The scope and methods of study were proposed to, and agreed upon, by FEMA, the communities and CF3R. Table 2, Stream Name Changes lists those streams whose name has changed or differs from that published in the previous FIS report for Orange County or any of the communities within. TABLE 2 STREAM NAME CHANGES Community Old Name New Name Unincorporated Area Cow Bayou Tributary Cow Bayou Lateral No. 14 Unincorporated Area Walnut Run Walnut Run Creek The study analysis includes coastline flooding due to hurricane induced storm surge. Both the open coast surge and its inland propagation were studied; in addition, the added effects of wave heights were also considered. 2.2 Community Description Orange County occupies an area of approximately 380 square miles in southeastern Texas. The study area is bounded on the north by Newton and Jasper Counties, on the east by the Sabine River and the State of Louisiana, on the south by Sabine Lake, and on the west by Hardin and Jefferson Counties. The City of Orange, the county seat, is located approximately 110 miles east of Houston and approximately 20 miles northeast of Port Arthur. The U.S. Bureau of the Census recorded the 2010 population of Orange County at 81,837, which represented approximately a 3.7 percent decrease from the 2000 census estimate of 84,966 (Reference 1). The majority of developed land in the county is primarily forest and agricultural land. Major urban, residential, and recreational areas are generally located in the extreme eastern and western portions of the county. Most commercial development extends along U.S. Interstate Highway 10 that runs east to west through the county. Major industrial development is located along the Sabine River. Leading industries in the area produce oil, timber, iron, steel and petrochemicals. A naval base and shipyard in the City of Orange contribute to the economy. Orange County is located in a humid subtropical climatic zone, which is characterized by moderate winters and warm summers. Rainfall is abundant and, on the average, is evenly distributed throughout the year. The hurricane season extends from June through October. The annual precipitation average is 56 inches, and the average humidity is 89 percent at 6:00 A.M. and 69 percent at 6:00 P.M. The annual average temperature is 68 F, with average temperatures ranging in January from a low of 42 F to a high of 61 F and in July from 74 F to 91 F. Soils in Orange County are clayey and loamy, have low to moderate infiltration rates, and produce a moderate to high runoff potential. The soils are classified into Soil Conservation Service Groups A, B, C, and D for hydrologic purposes. 4

9 Orange County is heavily wooded, with extensive wetlands along the Neches and Sabine River basins. Large stands of natural cypress in swamps exist north of the City of Orange along the lower Sabine River. Physiographically, Orange County lies within the Gulf Coastal Plain province, which is characterized by relatively flat terrain with level or nearly level areas in the floodplains, and higher areas in the northern portions of the county. The elevations in the county range from sea level to about 30 feet above sea level using the North American Vertical Datum (NAVD) of Some areas in Orange County have undergone minor subsidence due to continued groundwater withdrawal and the inelastic behavior of the underlying clay in those areas. The magnitude of the subsidence has been less than one foot (Reference 2). The major streams within Orange County are the Neches and Sabine Rivers; Adams, Cow, and Little Cypress Bayous; Caney, Ten Mile and Tiger Creeks; and Anderson Gully. The Sabine River, which forms the county's eastern border, rises in northwestern Hunt County and discharges into Sabine Lake at Orange County's southern border. It is about 579 miles long and drains about 9,756 square miles in eastern Texas and western Louisiana (7,426 square miles in Texas). It has an average annual flow of 8,700 cubic feet per second (cfs). The Neches River, which forms the county's southern border, rises southeast of Dallas and flows generally southeastward for 416 miles to Sabine Lake south of Vidor. It drains about 10,011 square miles and has an average annual runoff of about 7,200 cfs. Cow Bayou flows southward from Jasper County and empties into Sabine River near Bridge City. It drains about 174 square miles of mostly forested and undeveloped land. Sandy Creek and Cow Bayou Lateral No. 14 are the major tributaries of Cow Bayou. Adams Bayou drains approximately 85 square miles in southern Newton and eastern Orange Counties. Gum Gully, a tributary of Adams Bayou drains about 5 square miles. Little Cypress Bayou flows through the north end of the Orange study limits. The watershed comprises about 25 square miles of southeast Texas. Little Cypress Bayou Tributary is the major tributary of Little Cypress Bayou. Tiger, Caney, and Ten Mile Creeks drain watershed areas of 30, 12, and 48 square miles respectively. Anderson and Terry Gullies, small coastal streams with poorly defined channels, drain a total area of 24 square miles. The City of Orange, county seat of Orange County, is located in the southeastern region of Orange County. It occupies an area of approximately 21 square miles on the Texas-Louisiana border between the west bank of Sabine River and the east bank of Adams Bayou. Portions of the city extend west of the Cities of Pinehurst and West Orange, which lie on the west bank of Adams Bayou. The city also is bounded on the north and south by unincorporated areas of Orange County. The city is located approximately 20 miles northeast of Port Arthur. Orange was incorporated as a city in The U.S. Bureau of the Census recorded the 2010 population of Orange at 18,595, which represented a slight decrease from the 2000 census of 18,643. Physiographically, the City of Orange lies in the transition zone between the Gulf Coastal Plain and the East Texas Pineywoods. It has relatively flat terrain with level or nearly level areas in the floodplains, and higher areas in the northwestern portion of the city. The average elevation in the city is approximately 7 feet NAVD. There was a flood protection levee and floodwall system along the Sabine River; however the levee was damaged in Hurricane Rita in September The northern end of the 5

10 system ties into the embankment of Simmons Drive which, in turn, ties into the Interstate Highway 10 embankment. The southern end of the system ends downstream of the city, and is not tied to high ground. The major streams within the City of Orange are Adams Bayou, Little Cypress Bayou, and the Sabine River. The rate of runoff in the area is generally slow because of the small conveyance capacities of the natural channel conditions along the lower Sabine River and Adams Bayou. These small capacities cause floods to frequently exceed the bankfull stage for long periods of time. Three separate interior drainage areas exist behind the damaged levee and floodwall system. The Brownwood and Naval Station watersheds drain about 0.4 and 0.1 square miles of the City of Orange, respectively. Runoff from these basins is discharged to the Sabine by gravity drainage structures located along and in the damaged levee. Coopers Gully watershed drains about 1.6 square miles of the city. Coopers Gully flows southeasterly through the central portion of the city. Runoff from this basin is pumped to the Sabine River via a pump station located at the mouth of Coopers Gully. The City of Bridge City, incorporated in 1970, is located in the southern portion of Orange County. It occupies an area of approximately 5.4 square miles just north of Sabine Lake and is surrounded by unincorporated areas of Orange County. The city is located approximately 20 miles east of Beaumont and 5 miles southwest of Orange. The U.S. Census Bureau recorded the 2010 population of Bridge City at 7,840, which represented a 9.4 percent decrease from the 2000 census of 8,651 (Reference 1). Bridge City s major commercial developments are generally located along U.S. Highway 87. Leading industries in the area produce steel, rubber, petrochemical products, ships and concrete. Agricultural products such as timber, rice, and soybeans also contribute to the economy of the area. Physiographically, Bridge City lies in the transition zone between the Gulf Coastal Plain and the East Texas Pineywoods, on the watershed divide separating the Neches and Sabine Rivers. The terrain is relatively flat; its elevations are relatively low and range from about 5 to about 10 feet above NAVD 88. Substantial areas are less than 10 feet NAVD. The major stream within Bridge City is Cow Bayou. The Sabine River is to the east and the Neches River is to the southwest of the city. Since the city is located on the watershed divide between these two rivers, it is subject to only minimal flooding from them. Cow Bayou flows southward from Jasper County through the northeastern corner of Bridge City, and empties into the Sabine River at the swamp east of Bridge City. It drains about 174 square miles of mostly forested and undeveloped land. The rate of runoff in the Bridge City area is generally slow because of the small conveyance capacities of the natural channel along Cow Bayou. These small capacities cause floods to frequently exceed bankfull stages for long periods of time. The City of Pine Forest is located in the northwest portion of Orange County. It occupies an area of approximately 2.8 square miles. It is bounded by unincorporated areas of Orange County. The city is located approximately 70 miles northeast of Galveston, approximately 70 miles east of Houston, about 1 mile north of the City of Vidor, approximately 3 miles northeast of Beaumont, and 18 miles northwest of Port Arthur. The city's 2010 population was recorded at 487 people, which represents a 23 percent decrease from the 2000 census of 632 (Reference 1). The city is primarily a residential area which lies in the Gulf Coastal 6

11 Plain, in a forest wetland. It has flat terrain with relatively higher areas in the north central portion of the city. The elevations in the city range from 5 to about 25 feet NAVD. The major streams within the City of Pine Forest are Ten Mile Creek and Tiger Creek. Caney Creek lies to the south of the city. The Neches River flows approximately 4 miles west of the city. Ten Mile Creek flows south from Jasper County and empties into the Neches River 3 miles south of Pine Forest. It drains approximately 48 square miles. The western portion of the study area lies within this watershed. Tiger Creek, which flows southwest through the city drains approximately 30 square miles and empties into the Neches River 3 miles south of Pine Forest. The rate of runoff in the area is generally slow because of the small conveyance capacities of the natural channel conditions. These small capacities cause floods to frequently exceed bankfull stages for long periods of time. The City of Pinehurst is located in the southeastern portion of Orange County. It occupies an area of approximately 1.8 square miles near the Texas-Louisiana border, on the west bank of Adams Bayou, about 4 miles west of the Sabine River. It is bounded on the north and east by the City of Orange, on the south by the City of West Orange, and on the west by the unincorporated areas of Orange County. The U.S. Bureau of the Census recorded the 2010 population of Pinehurst at 2,097, which represented a 7.8 percent decrease from the 2000 census of 2,274 (Reference 1). The city is primarily a residential area whose economy is based on the commercial and industrial (petrochemical) activity of the City of Orange. Physiographically, the City of Pinehurst lies in the transition zone between the Gulf Coastal Plain and the East Texas Pineywoods. The zone has relatively flat terrain with level or nearly level areas in the floodplains. The elevations of the city are relatively low and range from sea level to about 10 feet NAVD. The major stream within the City of Pinehurst is Adams Bayou, which forms the city's eastern boundary. Adams Bayou flows southeasterly through the city and drains approximately 86 square miles in southern Newton and eastern Orange Counties. Hudson Gully, a small tributary of Adams Bayou, flows into Adams Bayou at the southern portion of the city. The drainage area of the gully is less than 2 square miles. The City of Rose City is located in the western region of Orange County. It occupies an area of approximately 1.7 square miles just east of the Neches River. The city is approximately 15 miles west of Orange, 80 miles east of Houston, 2 miles east of Beaumont, and about 13 miles north of Port Arthur. It is bounded on the north, south, west, and partially on the east by unincorporated marshland areas of Orange County. On the western border is Baird's Bayou. To the northeast, the city is bounded by the City of Vidor. The U.S. Census Bureau recorded the 2010 population of Rose City at 502. The population has been relatively stable since 2000 when the population was 519 (Reference 1). This population is expected to remain quite stable since there is little possibility of expanding the city limits because the area is mostly surrounded by swamp. Most of the work force of Rose City commutes out of town to plants or businesses, generally in Beaumont. However, Rose City does have steel and sheet metal fabricating plants, as well as a few small businesses. 7

12 The major stream within the Rose City is Tiger Creek. Tiger Creek, whose headwaters are in Jasper County, runs through the eastern part of the city and enters the marshes southeast of Rose City. Tiger Creek's watershed area of about 30 square miles drains the most westerly portion of Orange County. The small, narrow, poorly defined channel has a restricted conveyance capacity, causing extensive overbank flooding which generally lasts for periods of several days. Within Rose City corporate limits Tiger Creek is controlled by flooding from Neches River. The Neches River is about 1 to 1.5 miles west of the city. The Neches River originates from Van Zandt County, flows generally southeastward for 416 miles, and then empties into Sabine Lake at Port Arthur. There are also several small lakes and bayous within the city limits. The elevation of the land in Rose City ranges from about 5 feet to 13 feet NAVD. Because of this low elevation, and because the surrounding area is lowland swamp, high winds during storms restrict water from draining until the storms subside. When the waters are allowed to drain, they run south into the swamp, and subsequently into the Neches River. Most of the flooding in Rose City is caused by backwater from the Neches River, as well as from heavy rainfall ponding. When flooding occurs in Baird's Bayou on the western border of the city, the feeder road to Interstate Highway 10 also floods. This road is eight feet below the highway. Interstate Highway 10 also has some low bridges which become inundated during intense rains. Another road in the southern part of town frequently floods during heavy rainfall. This is due to the fact that it is located in a depression between the elevated railroad and another area of higher elevation. The City of Vidor is located in the western region of Orange County. It occupies an area of approximately 10.6 square miles, approximately 13 miles west of the City of Orange approximately 80 miles east of Houston, approximately 8 miles east of Beaumont, and about 20 miles north of Port Arthur. It is bounded on the north and east, and partially on the south and west, by unincorporated areas of Orange County. To the southwest it is bounded by the City of Rose City. The U.S. Census Bureau recorded the 2010 population of the City of Vidor at 10,579, which represented a 7.5 percent decrease from the 2000 census of 11,440 (Reference 1). The City of Vidor was incorporated in It was a residential community until 1974, when a steel mill was built to the southwest of the city and other industries followed. The city's major residential developments surround the business area. Relatively large residential areas and some important commercial establishments exist within the floodplains. Major business and commercial development extend along State Highway 105 between the Kansas City Southern Railroad and Interstate Highway 10. Leading industries in the area are steel and paper mills. Some ranching and farming of the fertile delta soil in the Vidor area also contribute to the city's economy. The city's rapid commercial and residential development is expected to continue. Physiographically, the city lies in the Gulf Coastal Plain. The zone has flat terrain with relatively higher elevations in the areas adjacent to the Neches River Delta marshland, and is surrounded by forest. The elevation of the city ranges from sea level near the marshlands to about 23 feet NAVD. 8

13 The major streams within the City of Vidor are Tiger Creek, Meyers Bayou, and Anderson and Terry Gullies. Tiger Creek, whose headwaters are in Jasper County, runs through the western part of the city and enters the marshes southwest of Vidor. Its watershed area of about 30 square miles drains the most westerly portion of Orange County. Meyers Bayou, with a watershed area of 3.3 square miles, enters the marshlands south of Vidor. Anderson Gully, with a watershed area of 10.4 square miles, flows through the center of the city and drains about 2 square miles of the city. Terry Gully, another small coastal stream, has a watershed area of 10.3 square miles. These streams encompass a total drainage area of about 52 square miles. Their small, narrow, poorly defined channels have restricted conveyance capacities, causing extensive overbank flooding generally for periods of several days. The Neches River flows about 2 miles west of the city. The City of West Orange is located in the southeastern region of Orange County. It occupies an area of approximately 3.2 square miles near the Texas-Louisiana border, on the west bank of Adams Bayou, about 1 mile west of the Sabine River. It is bounded on the north by the City of Pinehurst and on the east, south and west by the City of Orange. The city is located approximately 100 miles northeast of Galveston, approximately 110 miles east of Houston, and approximately 25 miles east of Beaumont. West Orange was incorporated as a city in The U.S. Census Bureau recorded the 2010 population of West Orange at 3,443, which represented a 16 percent decrease from the 2000 census of 4,111 (Reference 1). The city is primarily urban. Its major residential and commercial developments are generally located in the flat terrain that extends along Adams Bayou. Some homes have been built in the low floodplains of Adams Bayou. The city's economy is based on petrochemicals, the leading industry in the Orange area. Physiographically, the city lies in the transition zone between the Gulf Coastal Plain and the East Texas Pineywoods. It has relatively flat terrain with level or nearly level areas in the floodplains. The elevation of the city is relatively low and ranges from sea level to about elevation 10 feet NAVD. The major stream within the City of West Orange is Adams Bayou, which flows southward through the city and forms the city's eastern boundary. It drains approximately 86 square miles in southern Newton and eastern Orange Counties. Three small tributaries flow eastward throughout the city, and empty into Adams Bayou. These tributaries divided the City of West Orange into three sub-basins with areas less than one square mile. The FIRMs identify the tributaries as Adams Bayou Lateral No. 1, Adams Bayou Lateral No. 10 and Forman Road Ditch. The rate of runoff in the area is generally slow because of the small conveyance capacities of the natural channel along Adams Bayou, causing floods to frequently exceed bankfull stages for long periods of time. 2.3 Principal Flood Problems Flooding in Orange County results primarily from stream overflow (caused by rainfall runoff, ponding, and sheet flow), and from tidal surges and associated wave action (caused by hurricanes and tropical storms) transmitted through the streams. High tide levels can intensify the stream overflow caused by rainfall runoff. Because of the flatness of the terrain, many inland areas are characterized by shallow flooding during heavy rainfall. Not all storms which pass close to the study area produce extremely high tides. Similarly, storms which produce extreme conditions in one area may not necessarily produce critical conditions in 9

14 other parts of the study area. The Sabine River and nearby streams are estuarine, and under certain conditions tides generated at their mouths can intrude far upstream. Rainfall which accompanies hurricanes aggravates the tidal flood situation. Storms passing Texas in the vicinity of Orange County have produced severe floods as well as structural damage. Brief descriptions of several significant storms provide historic information to which flood hazards and flood depths can be compared (References 3, 4, 5, 6, 7, 8 and 9). April 25, 1913 The Sabine River crested at elevation 6.6 feet NAVD at the staff gage at the Gulf State Utilities Pier in the City of Orange. April to June 1953 Heavy rainfall, produced by two storms occurring in the same general area, followed a period of above normal rainfall that had greatly built up the moisture content of the soil. Rainfall from April 28 to May 5 was more than 11 inches in the Lower Sabine and Neches River basins. From May 11 to 19, this storm brought heavy rainfall to the Sabine River basin. From May 13 to 19, inches of rainfall was recorded in Orange. The storm caused extensive flooding in the lower areas. This storm caused homes to be flooded, buildings damaged, and roads inundated. There was minor flooding in downtown Orange on Water Street. The estimated velocities in the Sabine channel in the vicinity of Orange ranged up to 5 feet per second (fps); overbank velocities were lower (0.5 fps). The Sabine River was 6.2 feet NGVD. The staff gage at Gulf State Utilities Pier in the City of Orange reached 6.0 feet NAVD on May 24. Flood damage to the area was estimated at $460,000. June 27 to 28, 1957 (Hurricane Audrey) This first hurricane of the season hit the Louisiana coast near Cameron and passed inland with its center about 25 miles east of Sabine Pass. It was accompanied by 4 to 8 inch rains. Tide records at Sabine Lake near Port Arthur indicated a maximum water level of 4.8 feet above MSL, and a peak of 4.5 feet was recorded on the Neches River near Rose City. September 21 to 23, 1958 This storm produced inches of rain in 24 hours, and 18.5 inches in 2 days. (Unofficial records show 14 inches in 9 hours in the City of Orange). A privately maintained gage at Bridge City recorded inches on September 21 and a 2-day total of 18.5 inches of rainfall. There was serious flooding in areas along the unimproved section of Adams Bayou. Estimated damages in the cities of Orange, West Orange and Pinehurst were $630,000. Of this, about $320,000 in damage was to homes and buildings and about $240,000 to county roadways and structures. September 9 to 12, 1961 (Hurricane Carla) This hurricane, which made landfall near Port O Connor, flooded more than 1.5 million acres of land in Texas. Tide levels reached 9.4 feet NGVD along the northern shore of Sabine Pass. Tides caused the Sabine River to rise to 7.4 feet at the City of Orange, and near Cow Bayou, Bridge City was under approximately 7 feet of water. A storm surge level of 7.1 feet above MSL was reported at Port Arthur. Floodwater moved inland from the Gulf beaches for 15 to 20 miles and along the Neches River Valley to the vicinity of Rose City. 10

15 Flood levels reached 8.5 feet above the mouth of the Neches River, 7.9 feet near Port Neches, and 7.7 feet at Beaumont. Rainfall of 1.96 inches on the 11th and 12th in the City of Orange added to the flood conditions. Carla flooded 64 square miles of land in Orange County (18 percent of the total land area). Low-lying areas adjacent to the Sabine River were completely inundated by hurricane-driven waters. Unprotected areas at elevations of 7 feet or less were flooded, especially in the south side of the city and along Adams Bayou. Total damages were estimated at $1,707,000, of which $767,000 were attributed to tidal overflow. September 17 to 28, 1963 (Hurricane Cindy) This hurricane, which made landfall at High Island, brought 15.8 inches of rain in 24 hours in the Adams Bayou watershed. Adams Bayou reached a crest height of 8.22 feet NAVD about midway between the underclearance and floor level of the Southern Pacific Railroad Bridge. The Sabine River crested at 4.4 feet NAVD and Adams Bayou reached 8.2 feet NAVD on September 18th. The peak discharge (maximum runoff) produced on Cow Bayou near Mauriceville was 4,600 cfs. The torrential rainfall caused flooding and millions of dollars of damage to the Sabine-Neches area. Damages were estimated at $249,000 in Bridge City. June 25, 1968 Nine days of rainfall dropped more than 13 inches of water onto an already damp earth. Homes in the east and northeast areas of Vidor suffered flood damage. October 27 to 28, 1970 Estimated rainfall of 12 to 15 inches in a 24-hour period washed out bridges and flooded homes and underpasses. Caney Creek Road was reported to have been covered with about 5 feet of water during one period of the storm. The Cow Bayou gage near Mauriceville indicated a peak discharge of 4,420 cfs. April 19 to 24, 1979 Rainfall during this storm was recorded at more than 7 inches in Orange County, and caused flooding in many areas along the Neches and Sabine Rivers and Adams, Cow and Little Cypress Bayous. Most severely affected was the Lakeview area in the northwestern section of the county, where approximately 200 dwellings were damaged. The City of Vidor was the hardest hit area in Orange County, with $168, worth of damage to the city's roads and bridges, and flood damage to homes and automobiles. High water was also reported in the south Bridge City area. The Neches River crested at 11 feet NAVD near Rose City and Vidor (7 feet above flood stage), and the Sabine River crested at 1.3 feet above flood stage. July 25, 1979 (Tropical Storm Claudette) Tropical Storm Claudette, an upper air low pressure cell, originated in the Atlantic near Puerto Rico and moved westward into the Gulf of Mexico. It brought gale force winds and heavy rainfall to many parts of southeastern Texas, causing severe flooding along streams and coastal areas. Rainfall in Bridge City was estimated at 16 inches in 48 hours. In Orange County, power lines were down in some rural areas and home, road and agricultural damages were high. Major damage to 29 homes occurred in Orange County. High water in Adams Bayou caused some residential flooding in the Hillbrook Estates area in north Orange and also in the south Orange area. In the downtown area, water was reported 2 feet deep, and in the Riverside area up to 4 feet of water was reported. Cow Bayou and Adams Bayou overflowed their banks and flooded nearby low-lying areas. In Bridge City, the area around Ferry Drive and West Round Bunch Road was flooded when Cow Bayou overflowed its 11

16 banks. The southeast addition to the southeast of Bridge City was also flooded. Texas Highway 87 between Bridge City and Rainbow Bridge was under water. In Pinehurst, Adams Bayou overflowed its banks and some homes in the Camelot and Concord additions were flooded. There were nearly 33 inches of water on Camelot Drive. Mountain Drive, just east of Camelot Drive, was closed. There was also heavy flooding on many streets in Pinehurst. The streets in Vidor were flooded, but were generally passable. The Interstate 10 underpass was also flooded. In West Orange, Western and Austin Avenues were reported under water. Some of the city's low-lying areas were evacuated. July 13, 1994 Heavy rainfall produced widespread flooding. The roof of the Hillcrest Memorial Gardens building was damaged by the weight of water from the heavy rainfall. Total estimated damage was $55,000. September 27, 1996 Nearly nine inches of rain fell in less than six hours, resulting in significant flooding across Orange County. The hardest hit area was Vidor, where a housing complex on Highway 105 had several feet of water in it. Other areas with flooding included all the exit ramps and underpasses along Interstate 10. Estimated damage was $20,000. September 9 to 11, 1998 (Tropical Storm Frances) Tropical Storm Frances was the third tropical system to impact southeast Texas in 3 weeks, and caused the worst damage. Wind gusts in excess of 50 mph occurred along the coast on September 11 th, but most of the damage occurred from the high tides. At Sabine Pass, the tide reading reached 5.3 ft MSL, which was one of the highest tides in the previous 30 years. On top of the high tides, heavy rain lasting several days dropped 8 to 10 inches of rain across the region. At Sea Rim State Park, water got to the top of the dunes, which is 8 to 9 feet higher than normal. Offshore oil workers evacuated before 70 to 80 mph wind gusts impacted the rigs offshore. Many of these evacuees landed in Sabine Pass, and were caught in town due to the high tides. Sabine Pass was totally isolated from road traffic for three days due to high water. Nearly every home and business in Sabine Pass had salt water enter into them (over 70 structures). Highway 87 between Sabine Pass and Port Arthur received major damage, as did Highway 87 between Port Arthur and Bridge City, around the Rainbow Bridge. Pleasure Island received significant damage to the levee from the high tides and heavy wave action. The worst hit areas in Orange County included Bridge City and Vidor. Several roads were closed from September 11 th through the 13 th. Over 4,000 sandbags were passed out so homeowners could protect their homes from the high water. Estimated damage from Tropical Storm Frances was $7.0 million. March 4 to -12, 2001 The Sabine River had a major flood in early March, cresting five to six feet above flood stage between the 9 th and 11 th. Significant erosion occurred on the river bank, and many homes and camps immediately on the river were flooded. Many roads leading to the river were damaged from the rapidly moving water. Estimated damages were $300,000. June 5 to 6, 2001 (Tropical Storm Allison) Tropical Storm Allison caused minor problems along coastal sections of southeast Texas, but eventually resulted in catastrophic flood losses further inland. Wind gusts of 30 to 40 mph resulted in minor roof damage to less than ten homes along the coast in Orange County between the evening of June 5 th and the early morning hours of June 6 th. A two foot storm 12

17 surge resulted in minor beach erosion and portions of Highway 82 between Sabine Pass and Port Arthur to be under water during high tide during the nighttime high tide of June 5 th to 6 th. The specific flood events that occurred between June 7 th and 9 th were a result of the remnants of Tropical Storm Allison, as it meandered across southeast and east Texas. October 29, 2002 Over 600 homes across Orange County were flooded after 6 to 8 inches of rain fell in less than 6 hours. Of the 600 homes, around 300 were located in Orange, and 150 in Vidor. Total estimated damages were $3.0 million. September 23 to 24, 2005 (Hurricane Rita) Although Hurricane Rita made landfall just east of the Texas-Louisiana border, it moved northwest and moved across southeast Texas in the morning hours of September 24 th as a dangerous category 3 hurricane with sustained winds of 120 mph. Along the coast of Orange County, storm surges near 10 feet occurred near Sabine Pass, where over 90 percent of the homes were severely damaged or destroyed. The storm surge backed up the Sabine River, and flooded a small section of downtown Orange with around 4 to 5 feet of storm surge. Winds blew over 100 mph across the entire region, snapping and uprooting trees, and damaged over 125,000 homes and businesses. Total estimated property damage was $2.1 billion. October 16 to 21, 2006 Two day rain totals of 12 to 16 inches resulted in long duration flooding across portions of Orange County. The hardest hit areas were near Mauriceville, and along the Neches River near Lakeview. At least 40 homes were destroyed and another 60 were damaged. An abundance of moisture and high wind shear resulted in several tornadoes and flash floods across southeast Texas. Total estimated damage was $4.0 million. September 13, 2007 (Hurricane Humberto) Hurricane Humberto moved into Orange County around 3:15 A.M. between Vidor and Bridge City. Damage was primarily trees blown down, roof damage, and power lines downed. One fatality occurred in Bridge City. Power outages occurred to over 20,000 customers. Some flash flooding occurred in the urban areas between Beaumont and Orange. Highest estimated winds were around 80 knots or 90 mph, but hurricane-force wind only extended 15 miles. The lowest pressure reading was estimated to be 985 mb at landfall. Coastal storm tides were 3 to 5 feet, with the highest occurring at Texas Point. Total estimated damage was $10.0 million. August 5, 2008 (Tropical Storm Edouard) Tropical Storm Edouard produced minor wind damage and some coastal flooding along the southeast Texas coast before it made landfall around 7 A.M. CDT near McFaddin Wildlife Refuge in Jefferson County, Texas. The lowest pressure reading in southeast Texas occurred at Sea Rim State Park, where the barometer dropped to mb. The strongest wind gusts were mainly 50 to 70 mph across Jefferson and Orange counties, including 56 mph at Southeast Texas Regional Airport ASOS and 71 mph at the Texas Point gage. Rainfall totals were between 1 and 3 inches. The highest storm tides were between 2 and 5 ft MLLW, including 3.75 ft at Sabine Pass North and 4.66 ft at Texas Point. In Orange County, a few trees and power lines were blown down. Up to 700 customers lost power. Minor roof damage occurred to some homes and businesses. Total estimated damage was $250,

18 September 12 to 13, 2008 (Hurricane Ike) Hurricane Ike made landfall near Galveston, Texas early in the morning on September 13 th as a strong category 2 hurricane. Sustained hurricane force winds were measured in western Orange County. Hurricane Ike caused wind damage and significant storm surge flooding across southeast Texas. The highest recorded winds were at Southeast Texas Regional Airport with sustained winds of 70 mph and gusts of 96 mph. The lowest pressure reading also occurred at Southeast Texas Regional Airport, with a low of mb. Storm surge was significant. Sabine Pass had its highest water level recorded during Ike, with a maximum of ft MLLW. This storm surge almost topped the seawall around Port Arthur. Large waves did crash over the seawall, causing some flooding of homes within 3 blocks of the seawall. In Orange County, Bridge City had nearly all of their homes flooded (over 3,000), and this extended north to Rose City, and northeast to the city of Orange, where water topped the levee on the east side of town. Over 3,000 homes were also flooded in Orange. Maximum storm total rainfall was between 5 and 8 inches across Orange and surrounding counties. One fatality occurred during Ike due to a vehicle being swept off Highway 73 near Rainbow Bridge by the large storm surge and waves. Total damages were estimated to be at least $1.3 billion across southeast Texas. 2.4 Flood Protection Measures Several structural flood protection measures were constructed in Orange County. Reservoirs (such as Toledo Bend, Murvaul, and Tawakoni), in the Sabine Watershed, and flood retarding structures in the upper basin of the Sabine River, provide flood storage volume and assist in prevention of floods. In the Bridge City area, the Cow Bayou channel was enlarged in 1952 to a 13-foot depth and 100-foot width from its mouth to stream mile 6.7. The channel enlargement eased Cow Bayou from rainfall flooding but did not prevent surge intrusion. Additionally, channel improvements were completed by USACE on Adams Bayou. A diversion ditch north of Pinehurst traverses the Adams and Little Cypress Bayou watersheds and partially diverts runoff from the upper 32 square miles of Adams Bayou and 10 square miles of Little Cypress Bayou watersheds into the Sabine River. The City of Orange is partially protected from Sabine River floods by the locally-owned levee along Little Cypress Bayou and by an adjoining levee and floodwall along the Sabine River. The levee reduces the threat of flooding directly from Sabine River, but introduces some interior drainage problems. Also, the levee system does not prevent surge intrusion into Adams Bayou and resulting flooding of the surrounding low-lying areas. The levees in the vicinity of the City of Orange were damaged in storms and hurricanes during recent years, and are currently not certifiable and are not shown on the FIRMs. Nonstructural flood protection measures in the county consist of flood damage prevention ordinances, which were originally adopted by communities during the late 1970s and early 1980s. The ordinances place controls on the types of development and activities which are permissible in the floodplain. The National Weather Service provides forecasting and community flash flood warning services. 14

19 3.0 ENGINEERING METHODS For the flooding sources studied by detailed methods in the community, standard hydrologic and hydraulic study methods were used to determine the flood-hazard data required for this study. Flood events of a magnitude that is expected to be equaled or exceeded once on the average during any 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected as having special significance for floodplain management and for flood insurance rates. These events, commonly termed the 10-, 50-, 100-, and 500-year floods, have a 10-, 2-, 1-, and 0.2-percent chance, respectively, of being equaled or exceeded during any year. Although the recurrence interval represents the long-term, average period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than 1 year are considered. For example, the risk of having a flood that equals or exceeds the 1-percent-annual-chance flood in any 50-year period is approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in the community at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish peak discharge-frequency relationships for each flooding source studied by detailed methods affecting the community. Flood magnitude and frequency for areas subject to runoff flooding from the streams studied in detail were estimated using the Corps of Engineers HEC-1 Flood Hydrograph Package (Reference 10). Regionalized unit hydrograph and rainfall loss rate parameters were developed by hydrograph reconstitution studies using thirty storms in six gaged basins. The transposition of the HEC-1 model parameters from gaged to ungaged basins was based on hydrologic similarity, as assessed from soil maps (References 11 and 12), USGS topographic maps (Reference 13), aerial photos (Reference 14) and field reconnaissance. Urbanized watersheds were studied further using methodology developed by Beard (References 15 and 16). Rainfall data used to estimate flood discharges for the various frequency events were developed from hourly rainfall records from the National Climatic Data Center (Reference 17) and from TP-40 (Reference 18). The resulting "computational" storms used to generate peak discharges of selected frequency have depth-area-duration characteristics consistent with the Texas Gulf Coast area. The effects of flow restrictions due to culverts and excessive backwater have been included in the hydrology. Flood discharge-frequency estimates for the Sabine and Neches Rivers were taken from the previously published Bridge City Flood Insurance Study (Reference 19) prepared by the USACE. The profiles for the 0.2-percent-annual-chance flood on both Ten Mile Creek and Tiger Creek were controlled by the 0.2-percent-annual-chance flood of the Neches River, overtopping the drainage divide. Peak discharge-drainage area relationships for each stream studied in detail are shown in Table 3, Summary of Discharges. 15

20 TABLE 3. SUMMARY OF DISCHARGES DRAINAGE AREA (sq. miles) 10% Annual Chance PEAK DISCHARGES (cfs) 2% 1% Annual Annual Chance Chance 0.2% Annual Chance FLOODING SOURCE AND LOCATION Adams Bayou At Water Supply Canal Upstream of Orange 69.0 (36.5) 1 3,440 4,800 5,400 6,780 At F.M. 1006/Dupont Road ,180 5,870 6,630 8,330 Anderson Gully At North Feeder Interstate ,200 1,500 1,650 2,000 At South Feeder Interstate At Southern Corporate Boundary Limit At Kansas City Southern Railroad Bridge 3.9 (2.4) 1 1,350 1,650 1,850 2,200 Caney Creek At confluence with Tiger Creek ,460 3,370 3,750 4,520 Coon Bayou At confluence with Cow Bayou ,900 2,470 2,680 3,200 Coopers Gully At Pumphouse ,250 1,470 1,640 1,780 Cow Bayou At Farm Road ,290 10,300 11,900 14,900 At Roundbunch Road ,700 10,800 12,500 15,700 Cow Bayou Lateral No Gum Gully At confluence with Adams Bayou ,790 2,290 2,470 2,910 Hudson Gully At confluence with Adams Bayou ,120 1,360 1,470 1,640 Little Cypress Bayou At confluence with Little Cypress Bayou Tributary 12.3 (4.3) 1 1,700 2,080 2,330 2,800 At Little Cypress Creek 20.7 (10.3) 1 2,220 2,960 3,270 3,970 At Jacks Landing 25.1 (15.7) 1 2,470 3,370 3,750 4,620 Little Cypress Bayou Tributary At Little Cypress Creek 7.8 (6.4) 1 1,940 2,430 2,720 3,280 Meyers Bayou At Southern Corporate Boundary ,560 1,920 2,150 2,580 Neches River At Beaumont 10,000 60, , , ,000 Notes: 1 Effective drainage area contributing to the peak flow 2 Data not available / Not determined / Not computed 16