A watershed is the land area that ultimately drains rainfall runoff to a common outlet point, typically a creek or bayou in Jefferson County. If your home is located in the Taylor’s Bayou Watershed, rain that falls on your house will eventually end up in the Gulf of Mexico. Mother Nature designs and builds watersheds, largely determined by the topography or “lay” of the land. Jefferson County has three (3) major watersheds.
As defined by FEMA, a floodplain is “Any land area that is susceptible to being inundated by water from any source.” In Jefferson County, a floodplain is generally defined as an area flooded due to either a channel’s capacity being exceeded or due to a tidal storm surge.
The strictest area of regulation along both sides of a bayou or creek (including the main channel) because it moves the 1% (100-year) flood downstream, away from homes or businesses that it may have flooded.
A 100-year floodplain is an area of land that has a 1% chance of being inundated by floodwaters in a given year. The 1% (100-year) flood is a regulatory standard used to establish risk zones with varying risk probabilities, which are then used by insurance actuaries to compute the flood insurance premium rate. The Base Flood Elevation (BFE) is used as a benchmark to administer floodplain management programs, the National Flood Insurance Program (NFIP), and to set building requirements for new construction.
There are an infinite number of flood frequencies that can occur. The .2% flood is called the 500-year flood; the 2% flood is called the 50-year flood; the 10% flood is called the 10-year flood; the 50% flood is called the 2-year flood, etc.
Yes. Some flood hazards simply are not mapped on FEMA Flood Insurance Rate Maps (see questions on “ponding” and “overland sheet flow”), nor is every small tributary in the county included. The mapped floodplain is only an estimate of where flooding is predicted to occur given a set of parameters which include a hypothetical rainfall that occurs over a watershed for an assumed amount of time. During an actual rainstorm, natural conditions can result in greater amounts of rainfall or runoff, resulting in flood levels deeper and wider than shown on the FEMA Flood Insurance Rate Maps.
Detention basins are excavated areas of land where potentially damaging excess floodwater is temporarily stored and then drained over time as water levels recede. Because Jefferson County is pancake flat, most of its detention storage must be excavated at a substantial cost; still, Jefferson County Drainage District No. 6 makes extensive use of detention basins to reduce the risk of flooding. They are typically large regional facilities, several hundred acres in size.
As defined above, a detention basin is an area where excess stormwater is stored or held temporarily, and then slowly drains when water levels in the receiving channel recede.In essence the water in a detention basin is temporarily detained until additional room becomes available in the receiving channel. Detention basins are used extensively in Jefferson County region. There are thirtyeight (38) detention basins in operation within the District throughout Jefferson County.
A retention basin also stores stormwater, but retention storage implies a more permanent basis. In fact, water often remains in a retention basin indefinitely, with the exception of the volume lost to evaporation and soil absorption. This differs greatly from a detention basin, which typically drains after the peak of the stormflow has passed, sometimes while it is still raining. Retention basins, for the sake of flood damage reduction, are not common in the Jefferson County region; they are popular in parts of the country that have soils more amenable to this type of flood damage reduction measure.
A proposed development in DD6’s service area is required to incorporate detention in the plans and construction of the project or subdivision if a review of the development by DD6 determines that the development would have an adverse impact on surrounding areas. The requirements and design of on-site detention basins are defined in the DD6 Criteria Manual. These on-site detention basins become the responsibility of the developer to construct and maintain or may be maintained by the final landowner.
If subdivision flooding is due to out-of-bank rising water rather than localized sheetflow, it almost certainly originates upstream. This is why regional detention systems must be built to contain upstream water runoff due to urban development, enabling gradual floodwater release rates which are not damaging to downstream neighborhoods.
Hydrology is an engineering process used to convert a rainfall amount into a volume of water moving down a channel. This volume of water is then inputted to a hydraulic model and turned into a map of flooding areas using a computer model called HEC-HMS.
DD6 has more than 1,070 miles of predominately grass-lined bayous, creeks, and man-made drainage channels in the district. DD6 maintains nearly 785 miles of these channels along with 38 large stormwater detention basin sites in Jefferson County.
Our regular maintenance program includes mowing, selective clearing, hazardous tree removal, herbicide application in agricultural areas, tree pruning, care of concrete linings, and removing sediment and foreign materials that build up in our channels potentially affecting their ability to efficiently convey stormwater.
Multi-Service Areas include Cris Quinn Soccer Field, Folsom Hike and Bike Trail andGulf Terrace Hike and Bike Trail. These areas are mowed as needed for control of grass, which means keeping vegetation to less than 24 inches in height.
The District’s mowing program is intended to maintain cost-effective grass-lined channels, limit tree growth and other woody-stemmed vegetation that grow near the channel flow line, and provides open access for the inspection of slopes and other flood control infrastructure. DD6 accomplishes this with its current schedule mowing twice a year. In keeping with its mission statement, DD6 must prioritize its limited budget to reduce flooding risks and damages and to properly maintain our important drainage infrastructure. Flood damage reduction and health and safety – rather than beautification – is the goal.
Grass-lined channels convey stormwater very effectively; even tall grass will not prevent or significantly slow the channel flow. Soft grass stems bend with rapidly flowing water, allowing it to “get out of the way” during floods. (Visual observation after a rainfall event, once the water recedes, shows the grass lying down in the direction of the flow.)
DD6 does limit the presence of large woody-stemmed trees, shrubs and grasses within channel flow lines.
a) If your home or business is located within the City of Beaumont please contact the City of Beaumont Community Development Department at 409-880-3100.
b) If your home or business is located outside the City of Beaumont please contact the Jefferson County Engineering Department at 409-835-8584.
a) Please call our office at 409-842-1818 to make us aware of a maintenance need. Please be prepared to provide a description of the location. DD6 only maintains ditches, drainage channels and detention ponds on property owned by DD6 and those within an established drainage easement or right-of-way.