Common Terms Related to CCFCC’s Mission Objectives: Flooding, Preservation & Education

1% (Annual Chance) Flood: National Flood Insurance Program (NFIP) regulations define this as “the flood that has a 1% chance of being equaled or exceeded in any given year.” The terms “Base Flood” and “100-year Flood” mean the same. It is a function of rainfall amount, rainfall intensity, topography and other variables. The 1% annual chance flood standard has been used for nearly a century as the basis for many structural and non-structural floodplain management approaches.

1% (Annual) Storm: The amount of rain having a 1% chance of being equaled or exceeded in any given year. The rainfall amount and intensity is established by the National Weather Service. The amount of precipitation constituting a 1% storm varies by geographic location (i.e., the amount is much greater along the Gulf Coast than in the Texas Panhandle).


Acre-foot: The volume of water required to cover one acre of land (43,560 square feet) to a depth of one foot. An acre-foot of water is equivalent to 325,851 gallons or 1,233 cubic meters.

Aquifer: An underground reservoir. To tap the water in an aquifer, wells are dug until they reach the top layer of the water table, which has peaks and valley that echo the shape of the land above it. When large quantities of water are pumped from an aquifer, or during an extended dry spell, the water table is lowered. Groundwater for most communities and industries in the Cypress Creek Watershed comes from the Evangeline and Chicot aquifers. Aquifers do not have inexhaustible supplies of fresh water. They must be recharged. As population and industry demands increase, well water consumption increases and withdrawal reaches a point where the aquifer cannot replenish itself, resulting in land subsidence. In most areas, the Evangeline aquifer (one of the two primary aquifers in the Houston-Galveston region) is separated from the overlying Chicot aquifer by clay beds (visit for information on “Where is Earth’s Water?”). The Evangeline aquifer recharges by direct infiltration of rainfall in inter-stream, upland outcrop areas, and leakage from other aquifers such as the Chicot. The hydraulic conductivity of the Evangeline varies between twenty and one hundred feet per day. Because the Cypress Creek Watershed is in mostly unincorporated areas of Harris and Waller Counties, the majority of water wells drilled there are operated and maintained by local municipal utility districts (MUDs). The maximum depths of occurrence of freshwater in the Evangeline aquifer range from 150 feet above sea level to 2,250 feet below sea level. Its fresh water interval ranges in thickness from fifty feet to 1,900 feet. Wells drawing water from the Evangeline aquifer range in depth from 170 feet to 1,715 feet.

Annexation: To incorporate one territory into another political entity (e.g., a country, state, city or municipal utility district).

ASCE: American Society of Civil Engineers (for more information, visit
Association of State Floodplain Managers (ASFPM): CCFCC is a standing member of this organization of professionals involved in floodplain management, flood hazard mitigation, the National Flood Insurance Program, and flood preparedness, warning and recovery. ASFPM is a respected voice in floodplain management practice and policy in the United States because it represents the flood hazard specialists of local, state and federal government; the research community; the insurance industry; and the fields of engineering, hydrologic forecasting, emergency response, water resources. (for more information, visit

Association of Water Board Directors (AWBD)-Texas: A professional organization with over 620 members made up of municipal utility districts (MUDs), Water Control and Improvement Districts (WCIDs), Public Utility Districts (PUDs), Utility Districts (UDs) and Special Utility Districts (SUDs). Consultants servicing these districts may also join. The published objective of the AWBD-Texas is “to promote the enhancement of Texas water district operations and management. It is an advocacy group for utility districts.
Base Flood: See 1% (Annual Chance) Flood.

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Base Flood Elevation (BFE): This is the peak floodwater elevation expected to occur at any given location during a 1% (100-year) storm. The 1% annual chance was agreed upon in the late l960s as a level for determining where regulatory and National Flood Insurance Program flood management measures would be applied. The BFE for specific locations along the stream and tributary channels is shown on the Flood Insurance Rate Map (FIRM) at that location.

Bayou Preservation Association (BPA): A citizens’ group whose mission is to protect and restore the richness and diversity of our waterways through activism, advocacy, collaboration and education. BPA facilitates collaborative projects and public awareness about the region’s streams and bayous in order to foster watershed management, conservation, and recreation along Houston’s defining natural resource. BPA advocates a “watershed management” approach to flood control, which mitigates flooding by managing the amount of water leaving a watershed and also balances the needs for storage, conveyance, habitat, recreation and aesthetics (

Best Management Practices (BMP): BMPs are effective, practical, structural or nonstructural methods which prevent or reduce the movement of sediment, nutrients, pesticides and other pollutants from the land to surface or groundwater, or which otherwise protect water quality from potential adverse effects of silvicultural (forestry) activities. These practices are developed to achieve a balance between water quality protection and the production of wood crops within natural and economic limitations.

Brazos River Basin: Bordering the western edge of the Cypress Creek Watershed in Waller County, the Brazos River Basin is the longest and largest in Texas, meandering 1,050 miles from its headwaters in New Mexico to its mouth two miles south of Freeport in Brazoria County. The basin contains 44,642 square miles. Once considered a potential source of surface water to supplant well water in an effort to alleviate land subsidence in Harris County, this effort was abandoned for several reasons (


Capital Improvements Program (CIP): The Harris County Flood Control District CIP shows the amount of funding it has decided to spend each year during the next five-year period for selected flood mitigation projects. The CIP is submitted annually to Harris County Commissioners Court for approval. HCFCD uses a “category” system to prioritize where these funds will be spent. There are nine levels ranging from Category One (Federal Flood Damage Reduction Projects), which has the greatest priority, to Category Nine (Local Participation Projects) (

Carbon Sequestration: A term which describes processes that remove carbon from the atmosphere (i.e., photosynthesis by trees).

Center For Watershed Protection: An excellent source of information for stormwater flood managers (

Channel: The main part of the stream that carries the stormwater flow from the watershed.

Charlie’s Trees: A to-be-announced CCFCC preservation project.

Clean Water Act (CWA): The Clean Water Act is the cornerstone for surface water quality protection in the United States. The statute employs a variety of regulatory and non-regulatory tools to sharply reduce direct pollutant discharges into waterways, finance municipal wastewater treatment facilities, and manage polluted runoff. It does not deal directly with ground water or with water quantity issues (see Nonpoint Source Pollution and National Pollutant Discharge Elimination System below). For more information concerning the Clean Water Act jurisdiction and EPA /U.S. Army Corps of Engineers districts implementation actions following the U.S. Supreme Court’s decision in the Rapanos v. United States and Carabell v. United States ruling, click here to view a summary of the key points.

Clear Cutting: The removal of all trees and native flora, usually by urban land developers, to make way for the construction of streets, homes, water and sewer lines, stormwater sewers, and other infrastructure in addition to homes, shopping centers, parking lots, etc. In the absence of Harris County replacement regulations, the detrimental environmental impact of clear cutting has become a source of growing concern by the public and by environmental organizations…leading to growing preservation activity by land developers and by Harris County Commissioners Court in the undeveloped areas of the Cypress Creek Watershed (click here for photos of clear cutting forests surrounding Mercer Arboretum).

Compliance Period: The period that begins with the issuance of a Letter of Final Determination and ends when a new or revised Flood Insurance Rate Map becomes effective. During the compliance period, a community must enact and adopt new or revised floodplain management ordinances required for participation in the National Flood Insurance Program.

Comprehensive Drainage Plan (CDP): First completed in September 1999, this City of Houston engineering analysis contains information on existing storm sewer infrastructure (

Community Rating System (CRS): A program created by the National Flood Insurance Program (NFIP) to encourage communities to establish floodplain management projects that exceed the minimum federal standards required for NFIP participation.

Confluence: The point where two streams join together in their journey downstream to a larger body of water.

Conservation Easement: A conservation easement is used to exclude certain activities on private land such as commercial development or residential subdivisions. Its primary purpose is to conserve natural or man-made resources on the land. The easement itself is typically described in terms of the resource it is designed to protect (e.g., agricultural, forest, historic or open space easements). The easement is a legally binding covenant that is publicly recorded and runs with the property deed for a specified time or in perpetuity. It gives the holder the responsibility to monitor and enforce the property restrictions imposed by the easement for as long as it is designed to run. An easement does not grant ownership nor does it absolve the property owner from traditional owner responsibilities (i.e., property tax, upkeep, maintenance, or improvements) (

(visit for Harris County Precinct #4 Park Facilities List, including Little Cypress Preserve, a local conservation easement completed by Legacy Land Trust).

Cost-Benefit Ratio: A mathematical calculation comparison of the cost which would be incurred for design and construction of a proposed flood damage reduction project versus the cost savings (benefit) couched in terms of the cost of repair of future damages if the project is not constructed. If the estimated project cost is less than the future damages, the cost-benefit ratio test will be deemed to have been met. Cost-benefit analysis was first used by the Corps of Engineers in the l920s and l930s to justify flood control and dam projects.

Cubic feet per second (cfs): The rate of drainage flow of stormwater runoff in streams and rivers. It is equal to a volume of water one foot high and one foot wide flowing a distance of one foot in one second. One “cfs” is equal to 7.48 gallons of water flowing each second (i.e., if a car’s gas tank is two feet by one foot by one foot…or two cubic feet…then gas flowing at a rate of one cubic foot/second would fill the tank in two seconds).

Cypress Creek Flood Control Coalition: A non-profit 501(c)(3) alliance of municipal utility districts, homeowner associations and supporting individuals/businesses located within the Cypress Creek Watershed which was formed in l999 to collaborate with the government and private sectors for the purposes of flood damage mitigation, environmental preservation and effective communications, all on a regional basis (Click here to view charter).

Cypress Creek Watershed: By area, the largest of the twenty-two watersheds in Harris County. Its headwaters are in Waller County and its mouth is at the confluence of Spring Creek shortly before they flow into the West Fork of the San Jacinto River Basin and downstream to Lake Houston.

Cypress Creek Watershed Major Tributaries Study: Completed by the HCFCD and the Texas Water Development Board (TWDB) in 2002/2003, this is a regional drainage plan and environmental investgation for nine primary tributaries in the Cypress Creek Watershed. The final report is entitled Regional Drainage Plan and Environmental Investigation For Major Tributaries In The Cypress Creek Watershed. (Note: A CD copy of this report has been given to all CCFCC directors. Copies are available upon request). CCFCC hopes to obtain a clairifcation from HCFCD as to whether the multi-purpose recommended flood mitgation and environmental preservation plans contained in this study will be implemented or merely used as “guidance for future development.”

Cypress Creek Watershed Master Drainage Plan: A master regional watershed drainage plan prepared by Turner Collie & Braden, adopted by Harris County Commissioners Court in l984. It did not establish responsibility or identify potential funding for implementation. HCFCD has advised CCFCC that it is a “conceptual” plan for use on a voluntary basis. This plan serves as the official HCFCD flood mitigation plan as of 2007 (visit

Cypress Creek Watershed Stormwater Management Plan: A six-part flood plan undertaken by HCFCD in 2001 that covered nine major tributaries (See “Major Tributaries Study” below). When implementing this plan, the schedule was to be completed by 2005. Changes in how to accomplish the plan occurred after Tropical Storm Allison in 2001. If these implementation evolutions are indicative, it will not be completed before 2009 (See Flow, Page 3, a news pamphlet published by HCFCD, spring 2003).

Cypress Creek Watershed Flood Control Study: An engineering review to develop alternatives for flood control and mitigation measures along five reaches of the watershed between Aldine Westfield and U.S. Highway 290. Contracted to Turner Collie & Braden (Job No. 13-02326-011), the final report was issued in January 1995. None of the recommendations were implemented.


Detention Basin: A man-made change to the natural topography where the soil has been excavated to create a basin for temporary storage of stormwater. The “captured” stormwater is then released into drainage channels at a controlled rate, which reduces the volume of water flowing downstream from what would otherwise be left to nature. This flood mitigation technique reduces the height of the flood peak. Regional detention basins in Harris County are constructed by HCFCD using funds available under the approved CIP. “Detention ponds” are smaller and usually constructed by land developers as a requirement for obtaining a development permit. There are five regional basins in the Cypress Creek Watershed. They total 860 acres of which 100
acres have been excavated (Source: HCFCD).

Detention Release Rate: Stormwater runoff detention is considered a viable flood damage reduction method. Temporarily detaining a specified amount of runoff can significantly reduce downstream flood hazards. The main purpose of a detention facility is to store the excess storm runoff associated with the increased imperviousness resulting from urban development and to discharge this excess at a rate no more than the rate occurring when the land was in its natural state (see “Development”).

Development: As defined in National Flood Insurance Program (NFIP) regulations, development means “any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment or materials” (Ref: 44 CFR59.1).

Drainage Basin: Also called a watershed, this is a natural part of the land’s topography where rainwater flows downhill into streams, rivers, lakes and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins (i.e., the Mississippi River basin) contain thousands of smaller drainage basins.


Easement: Ownership of a piece of property may best be described as a “bundle of rights.” These rights include the right to occupy, use, lease, sell, and develop the land. An easement involves the exchange of one or more of these rights from the landowner to someone who does not own the land. Easements have been used for years to provide governments, utilities, and extractive industries with certain property rights. An easement provides the holder certain rights regarding the land for specified purposes while the ownership of the land remains with the private property owner.

Effective maps: A flood insurance rate map (FIRM) becomes effective six months after the date FEMA issues a letter of final determination (LFD).

Elevation Certificate: A certificate issued to a property owner by a professional surveyor, which shows the elevation of the bottom floor of a structure on a given property. FEMA’s new elevation certificate (approved for use effective February 13, 2006, through February 28, 2009) requires the certifier to provide the square footage of the enclosed area below the elevated floor and at least two photographs of the building if the elevation certificate is being used to obtain flood insurance. An electronic version of the form and instructions is available on FEMA’s website ( Elevations certified on or after January 1, 2007, must be submitted on the new form and must include photographs.

Erosion: As defined in National Flood Insurance Program (NFIP) regulations which states that erosion “means the process of the gradual wearing away of land masses.” This peril is not per se covered under the Program (Ref: 44 CFR 59.1) The erosion process is believed to be greater in the Cypress Creek Watershed than other watersheds in Harris County due to the high content of fine-grained “sugar sand” within the soil content. Erosion is a main cause of constant silt deposits which reduce the creek’s carrying capacity during flood events. The process is exacerbated by urban development including improper installation of new subdivision outfalls (e.g., Little Cypress at the Little Cypress Preserve and at Meyer Park where a $1.4 million repair and restoration project undertaken by HCFCD in response to a CCFCC investigation and request was nearing completion in 2006).

Extra Territorial Jurisdiction (ETJ): The ETJ of a city is that area of land outside the city limits of an incorporated municipality in which the city has certain unilateral annexation rights and the right to apply its zoning and sub-division ordinances (Article 1, Chapter 160, Acts of 58th Legislature 1963 as amended by Article 970a, Vernon’s Texas State Statutes). CCFCC estimates that 99% of the Cypress Creek Watershed lies within Houston’s ETJ.


Federal Emergency Management Administration (FEMA): The federal agency responsible for administration of the National Flood Insurance Program (NFIP).

Flood Insurance Rate Maps (FIRMs): A map that shows rivers, channels, and tributaries and their adjacent floodplains based on a 1% flood and sometimes floodplains based on a 0.2% (500-year) flood. FIRMs are used as a tool to help determine the risk of flooding for a property and to compute actuarial flood insurance rates. A word of caution: Some areas of flooding are not shown on the map. FIRMs are published by FEMA (visit (for more information, go to:

Flood Insurance Study Data (FIS Data): Compiled by using detailed hydrologic and hydraulic analysis to model the annual chance flood event, FIS Data is used to determine Basic Flood elevations (BFEs) and to designate floodways and risk zones employed under the NFIP program (the first FIS covering the Cypress Creek Watershed was adopted in September l985). After FEMA reviews and approves a draft FIS (usually prepared by a study contractor and modified by FEMA where appropriate), it releases the information to the public as a Preliminary FIS for review and comment during a statutory 90-day appeal period.

Floodplain: Areas of low-lying, normally dry land along the banks of rivers, streams, and bayou channels which are inundated when channel flow spills out-of-bank onto adjacent land. This occurs when an unusually large amount of rain falls in a matter of a few hours or days. The floodplain serves as a major component of the watershed needed to convey the water downhill to the sea. Floodplains are designated by the frequency of the flood that is large enough to cover them (i.e., the 10-year floodplain will be covered by the 10-year flood and the 100-year floodplain by the 100-year flood). Flood frequencies such as the “100-year flood” are determined by hydrologic engineers plotting a graph of the size of all known floods for an area and determining how often floods of a particular size occur. Another way of expressing the flood frequency is the percentage of the probability of flooding each year (i.e., the 100-year flood has a 1% chance of occurring in any given year). It is important to understand that these calculated frequencies are, 1) average intervals that can and do vary significantly, and 2) the calculation is a mathematical expression, not an exact science. Predicting the frequency of and the area expected to be inundated is a complex task. It is also important to understand that the 2-year, 10-year, 20-year, and 50-year floodplain areas all lay within the boundary of the 100-year flood plain. The risk of a home being flooded corresponds to the area in which it is located. (Note: A 100-year event is often referred to as a “1% storm event” because in any given year it has a 1% chance of occurring. It is also referred to as the base flood, defined below). Because of urbanization, the building of structures and paved roads causes more water to flow into the creeks, streams, and rivers instead of being absorbed by the soil (for gradual release). This phenomenon causes floodwaters to spread over a larger land area than would occur if left in the state created by Mother Nature. Without proactive mitigation, urbanization increases the size (dimensions) of the floodplain.
For more information click here to go to Wikipedia’s definition.

Floodplain Management Plan (FMP)
: Prepared by the City of Houston, July 2001 (

Floodplain Management Standards: Ordinance No. 2006-894, which regulates development in areas of the city that are designated as floodplains, was passed by Council August 30, 2006. As amended, it prohibits issuance of permits for development in floodways which would result in fill, new construction, additions to existing structures or substantial improvement of any structure within the floodway. Exceptions are allowed where protection of the health, safety and welfare of the general public is concerned (Ref: City of Houston’s Code of Ordinances: Development and Building Standards, Chapter 19, “Flood Prone Areas”).

Flood Risk Zones: Flood zones are geographic areas that FEMA has defined according to varying levels of flood risk. These zones are shown on the Flood Hazard Boundary Map or a Flood Insurance Rate Map (FIRM) covering the location where your house or business exists. Each zone reflects the severity or type of flooding in the area and is taken into account to determine the flood insurance premium for structures located in each zone (See definitions of the FEMA flood zones at the end of this Glossary). For comprehensive flood zone definitions, visit National Flood Insurance Program’s website (

Floodway: The channel of a creek, stream, river, or other watercourse and that portion of the floodplain area immediately adjacent to the stream banks which conveys the flowing water downstream during a base flood without cumulatively increasing the water surface elevation more than one foot. The floodway is the main artery through which stormwater moves on its journey from higher to lower levels of the watershed tributaries and main channel. For streams and other watercourses where FEMA has provided Base Flood Elevations (BFEs), but where no floodway has been designated, the community must review floodplain development on a case-by-case basis.
Floodway Encroachment Lines: The lines marking the limits of floodways on federal, state and local floodplain maps.

Freeboard: A safety factor usually expressed in “feet above a flood level” for purposes of floodplain management.

Future Conditions Flood Hazard Boundry study project: While participating as a member of the Stakeholders Committee under the HCFCD/FEMA TSARP project in 2002, CCFCC became aware that the flood maps being developed for expected publication in 2004 would be outdated by their publication date due to evolving changes in the floodplains/floodways within the rapidly developing Cypress Creek Watershed. The “Future Conditions” analysis will use the TSARP hydrologic and hydraulic computer models to simulate where this will occur and to what extent under full urban development conditions. The project is being accomplished by HCFCD’s Planning Department with CCFCC’s engineering consultant participating on the project team. PBS&J is the HCFCD engineering contractor (for more information, go to “Historical Milestones” on this website).


Glossary of Hydrologic Terms: A US Geological Survey website feature (

Geographic Information System (GIS): Computer programs used to store a wide variety of information, which link specific types of the stored data to specific geographic locations. Examples would be streets, bayous and channels, HCAD parcel data, contours, floodplains and all the data that supports the information such as names, location, etc. (Source: HCFCD).

Ground Water: Water that fills cracks, voids, and other openings in beds of rocks, sand and soil. Ground water is found in soils and sands that are able to retain water (much like a sponge) and is constantly replenished by rainfall or snow. Unlike surface water, which can be polluted and which must be treated before it is drinkable, ground water pumped from deep wells is naturally filtered. After chlorination, it’s ready to drink (unless contaminated by some other source). Once considered limitless, ground water levels can decrease as a result of excessive pumping. Each year, out of all rainfall, only about 5.3 million acre-feet are absorbed and “recharged” into the state’s aquifers. In 1996, the 9.9 million acre-feet of ground water pumped exceeded the natural recharge, for a net loss of 4.6 million acre-feet of ground water, a loss that may not be restored. In 1995, sixty-seven percent of the total water supply in the San Jacinto River Basin came from surface water; ground water supplied thirty-three percent. Because of higher demands and population in the region, the percentage of ground water used must be lowered to twenty percent of total water use by 2020 in order to control excessive pumping (Source: San Jacinto River Authority; visit

Groundwater Reduction Plan (GRP): The North Harris County Regional Water Authority (NHCRWA) and the West Harris County Regional Water Authority (WHCRWA) are each required to prepare a GRP in compliance with Houston-Galveston Subsidence District regulations. The plan includes a description of how they will achieve the required reduction in groundwater withdrawal by the deadline dates mandated by the HGSD.

Global Positioning System (GPS) Port-A-Measure (PAM) (GPS-PAM): The Houston-Galveston Subsidence District, in cooperation with the Fort Bend Subsidence District, owns and operates seven GPS-PAM trailers to record land surface elevation changes. Each trailer is equipment with a GPS receiver and is moved on a weekly basis to established location points. Observations are recorded every 10 seconds. The data is considered to be accurate to +/- one centimeter with a 95% confidence level.

General Reevalation Study (GRR): A US Army Corps of Engineers reporting process.


Houston-Galveston Subsidence District (HGSD): The Texas Legislature created HGSD in l977. Their mandate: To prevent land subsidence by managing the withdrawal of groundwater. This important function will help to minimize the threat of flooding, water well failures, water quality problems, and other property damage issues while protecting and preserving an important natural resource (visit

Harris County Flood Control District (HCFCD): The Texas Legislature created the HCFCD in l937. The enabling legislation (Section 59, Article XVI of the Constitution of the State of Texas) states that the District’s authority includes, “the control, storing, preservation, and distribution of the storm and flood waters, and the waters of the rivers and streams in Harris County and their tributaries; for domestic municipal, flood control, irrigation and other useful purposes, the reclamation and drainage of the overflow land of Harris County, the conservation of forests, and to aid in the protection of navigation on the navigable waters by regulating the flood and storm waters that flow into said navigable streams. The Commissioners Court of Harris County, Texas, is hereby designated as the governing body of such District and the agency through which the management and control of the District shall be administered, and it is hereby empowered to do any and all things necessary to carry out the aims and purposes of this Act” (click to view Sections 1 & 2 “Added Powers”). (

Harris County Flood Control Task Force:
The Task Force consists of thirty-two voting members. Its objectives are, 1) to advise and recommend to Harris County government, policies and programs that adequately protect homes and businesses from the hazards of flooding and that facilitate economic development, while conserving and using the resources we have for the present and future enjoyment of our citizens; 2) to create a method whereby the Task Force can best address itself to short-term and long-range questions; and 3) to report to the Harris County Commissioners Court as soon as recommendations are complete on each subject of inquiry. County Judge Robert A. Eckels’ recommendation to Harris County Commissioners Court that CCFCC be appointed as a Task Force member was approved during the July 27, 2004 session.

Houston-Galveston Area Council (H-GAC): A region-wide voluntary association of 133 local governments and locally elected officials in the thirteen-county Gulf Coast Planning region of Texas. H-GAC’s mission is to serve as the instrument of local government cooperation, promoting the region’s orderly development and the safety and welfare of its citizens. It is the regional organization through which local governments consider issues and cooperate in solving area-wide problems. Through H-GAC, local governments also initiate efforts in anticipating and preventing problems, saving public funds (

Houston’s Regional Forest: In 2001, the USDA Forest Service approved funding for a special project to build the tools and systems that will help state and local groups monitor and guide the development of the area’s green infrastructure. Houston’s Regional Forest project brought federal and state government researchers together with local planners, policy makers, and managers to analyze the region’s tree cover using field research and computer modeling (Ref: A Report of Structure, Functions, and Values, October 24, 2005).This is the first report documenting the contributions that trees make toward air pollution removal, carbon sequestration, and residential energy savings for the entire Houston region.

Houston Wilderness: Founded in 2002 as a 501(c) (3) organization to encourage land conservation and preservation. CCFCC is a member.

Houston Voters Against flooding (HVAF): A non-partisan political action committee dedicated to making flooding a front-burner political issue in the Houston area by increasing awareness, organizing voters, and by proposing solutions to this problem (

Hydrograph. There are two meanings for hydrographs, both coming from hydro- meaning water, and -graph meaning chart. A hydrograph plots the discharge of stormwater in response to a storm event over a period of time. It portrays the rate of stormwater runoff measured in terms of cubic feet per second (cfs) (click to view hydrograph at the confluence of a tributary in Upper Cypress Creek). Terminology used to describe a hydrograph:
• Rising limb – The part of the hydrograph up to the point of peak discharge.
• Falling limb – The part of the hydrograph after the peak discharge.
• Peak discharge – The highest point on the hydrograph when there is the grreatest amount of water flow.
• Lag time – The difference between the peak rainfall and peak discharge.
Hydrologic Analysis/Modeling: The TSARP computer model is a Windows-based, HEC-HMS (similar to HEC-1).

Hydraulic Analysis/Modeling: The TSARP computer model is a Windows-based HEC-RAS (computation similar to HEC-2).


IGCC Technology (IGCC): A clean coal technology that combines two technologies (coal gasification and combined cycle) to offer the potential to achieve the environmental benefits of gas-fired generation with the thermal performance of a combined-cycle plant, yet with the low-fuel cost associated with coal (visit

Impervious Cover: The amount of land cover in roads, buildings and parking lots, and turf grass cover in a watershed which can seriously impact biotic integrity in associated streams. Methods are being developed to estimate and project impervious cover and turf grass area in small watersheds based on regionally available data. These estimations and projections will be used to guide monitoring and focus educational efforts on the importance of watershed management in developing localities.

Infiltration: The downward movement of water from the land surface into soil or porous rock. It is the primary process by which aquifers in the Cypress Creek Watershed and in Harris County are replenished.


Katy Prairie Conservancy (KPC): A non-profit land trust founded in l992 charged with ensuring the protection of a portion of the Cypress Creek Upper Watershed in perpetuity for the benefit of its wildlife and all Texans. Its land use is dedicated to mitigation of stormwater flooding in the lower Cypress Creek Watershed (below U.S. Highway 290 extending downstream beyond Cypress Creek’s confluence with Spring Creek).
KPC’s Mission: Preserve, protect, and enhance critical and sustainable portions of the Katy Prairie ecosystem which includes:
• Protecting between 30,000 and 60,000 acres of the Katy Prairie, primarily in its current agricultural state, and with some appropriate portions enhanced as wetlands and restored prairie habitat.
• Involving the local community and all stakeholders in the Katy Prairie Conservancy including hunters, conservationists, landowners, local residents, farmers and developers.
• Responsible stewardship of protected land.
• Conducting and facilitating research needed for the accomplishment of their mission.
• Promoting ecotourism and other economic incentives for conservation on the Prairie.
• Educating the public about the Katy Prairie.


Land Subsidence: As defined in the bill creating the NHCRWA, subsidence means lowering the surface elevation of the land by withdrawal of groundwater. Land subsidence occurs when the surface of the land sinks, a phenomenon which is occurring throughout Harris and Galveston counties and, to a lesser degree, surrounding counties in the metroplex. It is caused by pumping water, oil, and gas from underground pockets in volumes which exceed the aquifer’s natural replenishment rate such that it reduces the pressures causing (in the case of water) the clay layers of the aquifer to collapse. In the l950s and 1960s, community leaders began to link the increased frequency and severity of stormwater flooding to subsidence. Investigations revealed an alarming need to reduce our reliance on underground water and switch to surface water sources (such as streams and lakes). In 1977, government action led to creation of the Houston-Galveston Subsidence District (HGSD) as the regulatory agency charged with this responsibility. In 1999, the Cypress Creek Flood Control Coalition endorsed the HGSD’s undertaking as one of the key actions in its charter to provide the community stewardship to establish an integrated approach to solutions for stormwater flooding, land subsidence, and preservation of environmental resources on a regional basis throughout the watershed. (visit

Land Use Change: Cited in many environmental study projects as being the greatest threat to preservation of the area’s forests, wetlands, and exacerbation of stormwater flooding.

Legacy Land Trust (LLT): The Legacy Land Trust was formed in 1996 as an offshoot of the Bayou Preservation Association (a group dedicated to protecting the bayou systems of the Houston Metroplex through land conservation agreements). LLT encourages stormwater management and the preservation of area bayous for use as parks, hike and bike trails, and urban wildlife corridors. It also works to identify and recognize the hazards of construction in floodplains.

Letter of Final Determination (LFD): A letter sent by FEMA to the community stating that a new Flood Insurance Rate Map (FIRM) will become effective in six months and that each participating community compliant floodplain management ordinance must be adopted by that effective date (on December 18, 2006, FEMA released a Letter of Final Determination, which was the final step in the Tropical Storm Allison Recovery Project (TSARP). As a result of this letter, the Revised Preliminary Flood Insurance Rate Maps will become the effective maps for Harris County at the end of a six-month regulatory adoption period).

Light Detection and Ranging (LiDAR): Using the same process as radar, a LiDAR instrument transmits light out to a target. The tramsmitted light interacts with and is changed by the target; some of the light is reflected back to the instrument where it is analyzed (LiDAR was used to determine the elevation of the topography in the process of creating new FIRMs under the TSARP project). There are three basic generic types of LiDAR:
• Range finders.
• DIAL (Differential Absorption Lidar).
• Doppler lidars.

Letter of Map Amendment (LOMA): For a LOMA to be issued removing a structure from the Special Flood Hazard Area (SFHA), National Flood Insurance Program (NFIP) regulations require that the lowest adjacent grade (the lowest ground touching the structure) be at or above the 1% annual chance flood elevation. To remove the entire lot, the lowest point on the lot must be at or above the 1% annual chance flood elevation.

LOMC: A letter which reflects an official revision to an effective National Flood Insurance Program (NFIP) map. It is issued in place of the physical revision and republication of the effective map.

Letter of Map Revision (LOMR): It documents FEMA’s modification to an effective Flood Insurance Rate Map (FIRM), or Flood Boundary and Floodway Map (FBFM), or both. LOMRs are generally based on the implementation of physical measures that affect the hydrologic or hydraulic characteristics of a flooding source and thus result in the modification of the existing regulatory floodway, the effective Base Flood Elevations (BFEs), or the Special Flood Hazard Area (SFHA). The LOMR officially revises the Flood Insurance Rate Map (FIRM) or Flood Boundary and Floodway Map (FBFM), and sometimes the Flood Insurance Study (FIS) report, and when appropriate, includes a description of the modifications. The LOMR is generally accompanied by an annotated copy of the affected portions of the FIRM, FBFM, or FIS report. In December 2005, FEMA notified Harris County Judge Robert Echols that the CCFCC appeal seeking correction of significant calibration deficiencies in the preliminary FIRMs was denied. Subsequent negotiations/discussions among FEMA, the HCFCD, and CCFCC concluded with FEMA stating that they would proceed with issuance of the deficient FIRMs with the understanding that HCFCD, CCFCC, and other community organizations seeking the change would provide what is required to justify such a change, and FEMA would do so through issuance of a LOMR. At this time (January 2007), it is expected the LOMR will be issued within the next nine months. All requests for changes to effective maps, other than those initiated by FEMA, must be made in writing by the Chief Executive Officer of the community or an official designated by the CEO. Because a LOMR officially revises the effective NFIP map, it is a public record that the community must maintain. Any LOMR should be noted on the community’s master flood map and filed by panel number in an accessible location.


Map Modernization: Over the years, many of the government’s flood insurance maps became obsolete due to urban growth, changes to river flow and coastlines, and even flood mitigation efforts like drainage systems and levees. Accurate information is essential to inform property owners of emerging flood risks and to determine appropriate premium rates for flood insurance coverage. FEMA’s map modernization program, including creation of digital flood insurance rate maps (DFIRMs) is their response to the need to update and maintain flood hazard maps. DFIRMs will become the platform for identifying other potential risks such as land erosion, deforestation and ice flows (Source: Note: The TSARP remapping throughout Harris County and North Carolina are the first areas in the United States to undergo this initiative.

Multi-use: A term used by HCFCD in the TWDB/HCFCD final report, Regional Drainage Plan and Environmental Investigation For Major Tributaries in The Cypress Creek Watershed. Quoting from HCFCD publications, it denotes, “the ability to provide more than one use. This usually is in reference to drainage facilities that not only provide for drainage uses, but can accommodate other uses such as hike-and-bike trails, sports fields, wildlife habitat, etc.”

Municipal Utility District (MUD): A political subdivision of the State of Texas authorized by the Texas Commission of Environmental Quality (TCEQ) to provide water, sewage, drainage and other services within the MUD boundaries. A MUD is created by a majority of property owners in the proposed district petitioning the Texas Commission of Environmental Quality to create a MUD. The TCEQ evaluates the petition, holds a public hearing, and grants or denies the petition. After approval, the TCEQ appoints five temporary members to the MUD’s Board of Directors until an election is called to elect permanent Board members, confirm the MUD’s creation, and authorize bonds and taxing authority for bond repayment. Visit the TCEQ to look up municipal utility district info:


National Environmental Protection Act (NEPA): NEPA is the basic national charter for protection of the environment. It establishes policy, sets goals, and provides means for carrying out the policy.

National Flood Insurance Program (NFIP)
: In 1968, Congress created the National Flood Insurance Program (NFIP) in response to the rising cost of taxpayer funded disaster relief for flood victims and the increasing amount of damage caused by floods. The NFIP makes federally-backed flood insurance available in communities that agree to adopt and enforce floodplain management ordinances to reduce future flood damage. National Flood Insurance is available in more than 19,000 communities across the United States and its territories. The NFIP is managed by the Federal Emergency Management Agency’s Federal Insurance Administration and Mitigation Directorate. The Federal Insurance Administration manages the insurance component of the NFIP and works closely with FEMA’s Mitigation Directorate, which oversees the floodplain management aspect of the program. The NFIP, through partnerships with communities, the insurance industry, and the lending industry, helps reduce flood damage by nearly $800 million a year. Further, buildings constructed in compliance with NFIP building standards suffer seventy-seven percent less damage annually than those not built in compliance (and every three dollars paid in flood insurance claims saves one dollar in disaster assistance payments). The NFIP is self-supporting for the average historical loss year, which means that operating expenses and flood insurance claims are not paid for by the taxpayer, but through premiums collected for flood insurance policies.

National Geodetic Survey (NGS): Provides the benchmarks used to measure land subsidence.

National Pollutant Discharge Elimination System (NPDES)
: As authorized by the Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States. Point sources are discrete conveyances such as pipes or man-made ditches. Individual homes that are connected to a municipal system, use a septic system, or do not have a surface discharge do not need an NPDES permit; however, industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters (visit

North Harris County Regional Water Authority (NHCRWA): Created by the Texas Legislature in 1999 under House Bill 2965 (and subsequently ratified by the voters in January 2000), it’s purpose is to provide surface water, piped from Lake Houston, to MUDs located within its boundaries in order for the MUDs to comply with regulations mandated by the HGSD to reduce land subsidence (Also see West Harris County Regional Water Authority).

“No Adverse Impact”: A floodplain management initiative which represents a way to prevent worse flooding in the community by not increasing flood damages to other properties.
Nonpoint Source Pollution (NPS): Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution occurs when rainfall drains over or seeps through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into bayous, creeks, rivers, wetlands, coastal waters, and even underground sources of drinking water. These pollutants include:
• Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas.
• Oil, grease, toxic chemicals and trash from driveways, streets, express freeways, shopping centers, strip malls and other urban development.
• Sediment from improperly managed construction sites, crop and forest lands, and eroding stream banks.
• Salt from irrigation practices and acid drainage from abandoned mines.
• Bacteria and nutrients from livestock, pet wastes, and faulty septic systems.
• Atmospheric deposition and hydromodification.
As amended in 1987, the Clean Water Act has paid increased attention to nonpoint source pollution. It provides for states to prepare reports and propose management plans for the control of nonpoint source pollution for approval by the EPA, and encourages the development of plans on a watershed-by-watershed basis. Nonpoint source pollution control is a key element in design of the multi-purpose flood mitigation infrastructure described in the completed Cypress Creek Stormwater Major Tributaries Plan and the evolving Cypress Creek Stormwater Master Program being developed by HCFCD.


Over-flow: A major concern in Cypress Creek Watershed flood management is when, during heavy rainfall events, floodwater in Upper Cypress Creek overflows into Addicks Reservoir and eventually Buffalo Bayou (and into Houston’s central business district). The need to control release rates from the reservoir during flood events is critical to developments along the reservoir fringes and for major thoroughfares like State Highway 6. This concern has prompted sub-regional planning on the major tributaries draining into Addicks. CCFCC believes that the original design (early 1940s) of Addicks Reservoir by the Corps of Engineers took this overflow into account and sized Addicks accordingly. Nevertheless, HCFCD engineers continue to study this phenomenon and how best deal with it.


Ponding: The result of run off or flows collecting in a depression that may have no outlet, subterranean outlets, rim outlets, or man-made outlets such as culverts or pumping stations. Impoundments behind man-made obstructions are included in this type of shallow flooding as long as they are not backwater from a defined channel or do not exceed three feet in depth.

Preferred Risk Policy: This type of policy is available under the National Flood Insurance Program (NFIP) only in the B, C, and X flood zones (subject to the property meeting certain flood history conditions). It is not available in Special Flood Hazard Areas (SFHAs).


Rapanos/Carabell: Two important cases concerning wetland issues, which pose an environmental challenge to the Clean Water Act. Heard by the U.S. Supreme Court on 6/19/06 (visit
Recharge: The process which occurs when water is added to an aquifer. For instance, rainfall that seeps into the ground and into the aquifer is recharge.

Reclaimed Wastewater: Treated wastewater that can be used for beneficial purposes, such as irrigating certain plants.

Recycled Water: Recycled water is used more than one time before it passes back into the natural hydrologic system.

Regeneration: Renewing tree cover by establishing young trees naturally or artificially, promptly after the previous stand of trees or forest has been removed. Regeneration  includes practices such as changes in plant density through human-assisted natural regeneration, enrichment planting, reduced grazing and changes in tree provenances/genetics or tree species.

Regional Water Planning Groups (RWPG): Established in l998 as part of the implementation of Texas Senate Bill One enacted by the Legislature a year earlier, the TWDB divided the state into 16 regions..  The groups prepare regional water plans for their respective areas, which include estimating water demands in their area for the next fifty years.  The first plans were submitted in January 2001 and must be updated every five years (Source: Your Water Supply, Lone Star Chapter Sierra Club, 2003; for additional information visit:

Regulatory Floodway: A term used in FEMA’s National Flood Insurance Program (NFIP) regulations meaning the channel of a stream and the adjacent land areas “that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation to more than a designated height.”

Retention Basin: A basin designed to hold stormwater on a permanent basis. The HCFCD does not utilize this approach in their flood mitigation projects. HCFCD and CCFCC support the use of “detention” methods.
Riparian Corridor: The word “riparian” is derived from Latin ripa, meaning river bank. Riparian zones may be natural or engineered for soil stabilization or restoration. These zones are important natural biofilters protecting aquatic environments from excessive sedimentation, polluted surface runoff and erosion. They supply shelter and food for many aquatic animals and shade that is an important part of stream temperature regulation. When riparian zones are damaged by construction, agriculture or silviculture, biological restoration can take place usually by human intervention in erosion control and revegetation. Because of their prominent role in supporting wildlife, riparian corridors are often the subject of government protection. Research shows riparian zones are instrumental in water quality improvement for both surface runoff and water flowing into streams through subsurface or groundwater flow.

Risk Zones (See Flood Risk Zones): Zones designations used in flood regulations and for establishing insurance premiums under the National Flood Insurance Program (i.e., Zones AE, A1-30, AH, AO, VE, and V1-30).

Right-of-Way (ROW): An interest in real property, either in fee or easement (see “Easement”).

Run Off Rate: The amount and time during which a portion of precipitation, especially rain or melted snow, flows over a land surface while draining to a creek or other tributary. The run off volume and rate increases dramatically when forested land is converted to concrete and other non-porous surfaces during the urban development process.


San Jacinto River Authority: The Upper San Jacinto River Basin (above Lake Houston) contains thirteen major watersheds. The Cypress Creek Watershed is one of them.

Sheet Flow/Sheet Flooding: A condition where stormwater run off forms a sheet of water flowing across the land surface in areas where there are no clearly defined channels. Houses constructed with the ground floor only slightly above the outside grade are more likely to have stormwater enter than those which are constructed with higher slabs and good stormwater drainage.  The probability of flooding due to sheet flow is not shown on the FEMA flood maps for Harris County (with a few exceptions).

Silviculture: The art and science of controlling the establishment, growth, composition, health, and quality of forests to meet diverse needs and values of landowners and society.

Special Flood Hazard Area (SFHA): An area defined on a Flood Insurance Rate Map with an associated risk. A SFHA is defined as an area of land that would be inundated by the base, or 1-percent chance, flood. A structure located within an SFHA shown on an NFIP map has a 26-percent or greater chance of suffering flood damage during the term of a 30-year mortgage (Souce:

Square Mile: Equal to 640 acres or 43,560 square feet.

Strategic Partnership Agreement (SPA): Agreements between the City of Houston and Municipal Utility Districts located outside the city limits whereby the parties agree to impose and share equally a one-cent sales and use tax on an equal basis and the City agrees not annex the District for a minimum 30-years after the agreement is executed. The SPA provides that the District shall use such sales and use tax revenue only for the purposes for which the District is lawfully authorized to use its ad valorum tax revenues or other revenues. Section 6.01 provides that “the District shall take one or a combination of certain specified actions” which includes, “Accelerate the development of the water, wastewater, and drainage systems in the District…as necessary to encourage private investment in new construction in the District.”

Stormwater Detention Release Rate: (see “Detention Release Rate”).

Subsidence: (see “Land Subsidence”).

Substantial Damage: A term used in the National Flood Insurance Program (NFIP) regulations, which means “damage of any origin sustained by a structure whereby the cost of restoring the structure to its pre-damaged condition would equal or exceed the market value of the structure before the damage occurred.”
Sugar Sand: Found in abundance in the Cypress Creek Watershed, sugar sand is a fine silt comprised of ultra-fine mineral sand with a large percentage of organic granules. Because of its lightness it can easily form quicksand in hollows. Even when dry, sugar sand tends to be too light to drive across and can be hazardous to machinery. It is a key contributor to erosion in the watershed.


The City of Houston Stormwater Management Plan (SWMP): (visit

Texas Commission on Environmental Quality (TCEQ): The state’s primary environmental regulatory agency (visit

Texas Legislature: (for useful information, visit

Texas Water Development Board (TWDB): The board’s mission is to provide leadership, technical services, and financial assistance to support planning, conservation, and development of water in Texas. TWDB has two goals: First, to plan and guide the conservation and orderly, cost-effective development and management of the state’s water resources for the benefit of all Texans; second, to provide cost-effective financing for the development of water supply, for water quality protection, and for other water related projects (visit

Texas Windstorm Insurance Association (TWIA): Texas Association of Independent Insurance Agents.
Topography: The natural and man-made surface features of the land. These natural features include hills, valleys, streams, and lakes. Man-made actions which change the natural topography include, 1) construction of roads, subdivisions, shopping centers and other forms of urban development, and 2) withdrawal of underground water in excess quantities such that land subsidence occurs.

Topography: The natural and man-made surface features of the land. These natural features include hills, valleys, streams, and lakes. Man-made actions which change the natural topography include, 1) construction of roads, subdivisions, shopping centers and other forms of urban development, and 2) withdrawal of underground water in excess quantities such that land subsidence occurs.

Total Maximum Daily Load (TMDL):  The amount of a particular pollutant that a given stream or other body of water can “handle” without violating state water quality standards. Once a TMDL is established, responsibility for reducing pollution among both point sources (pipes) and diffuse sources is assigned. Diffuse sources include but are not limited to run-off (urban, agriculture, forestry, etc.), leaking underground storage tanks, septic systems, stream channel alteration and damage to a riparian area.  Responsibility for compliance ultimately includes everyone who lives, works and plays in a watershed that drains into an impaired water body.

Tributary Watershed: The land area that drains to a smaller stream which flows to the main channel of the watershed (i.e., stormwater drainage within Faulkey Gully’s tributary watershed ultimately flows into Cypress Creek).

Tropical Storm Allison Recovery Project (TARPS): A joint project by FEMA and HCFCD, created in 2001 to help Harris County recover from Tropical Storm Allison and to minimize damages from future floods by developing more current and accurate flood hazard information. This included investigation and development of new Flood Insurance Study (FIS) and Flood Insurance Rate Maps (FIRMs). The processing of appeals was completed in late 2005/early 2006. The Letter of Final Determination was expected to be issued in December 2006, but it has been delayed for an undetermined period of time.


United States Army Corps of Engineers (USACE): Among other things, the Corps of Engineer’s mission is to provide quality, responsive engineering services to the nation including: Planning, designing, building and operating water resources and other civil works projects (navigation, flood control, environmental protection, disaster response, etc.) (visit

United States Geological Survey (USGS): Part of the Department of the Interior, the USGS collects water level and subsidence measurements as part of a cooperative agreement with the Houston-Galveston Subsidence District. USGS scientists pioneered hydrologic techniques for gauging the discharge in rivers and streams and modeling the flow of complex ground-water systems.

Upper Watershed: When the term “Upper Watershed” is used discussing the Cypress Creek Watershed, it generally means the drainage area located upstream from the U.S. Highway 290 bridge crossing. Flooding in the communities downstream from the North Eldridge Parkway (the “Lower Watershed”) is, with few exceptions, a function of the upstream flood mitigation infrastructure (or lack thereof). Because drainage and stormwater flooding are both a system and a regional function, the size of the drainage areas and land-use upstream in relation to the total watershed must be clearly understood.

Following is a quick overview of these drainage areas, all of which funnel water downstream past the Interstate 45 bridge:
Sub-Watershed Square Miles %
• Little Cypress Creek 52.3 16%
• Mound Creek 35.6 11%
• Remainder of Upper Watershed 107.9 34%
• All remaining areas (Lower Watershed) 123.7 39%
• Total Cypress Creek Watershed 319.5 100%

Urban Development: The term “development” as defined in the National Flood Insurance Program (NFIP) regulations is “any man-made change to improved or unimproved real estate, including but not limited to buildings, or other structures, mining, dredging, filling, grading, paving, excavation or drilling operation or storage of equipment or materials.”

Urban Design Standards: See Iowa Statewide Urban Design Specification, Section 8, Storm Runoff Detention (visit

Urban Forest Effects Model (UFORE): A computer model used in analysis during the “Houston’s Regional Forest” project.

Urban Stormwater Management Study: This study (also called Flood-Wise), is local government’s response to CCFCC’s advocacy efforts in 2003-04. The coalition and other community organizations were convinced that the detention outlet “flow release rate” specified in HCFCD regulations was (and continues to be) excessive when applied to urban development in the Cypress Creek Watershed. The collaborative effort sought local government approval of and funding for a peer review to be done by an independent technical expert. HCFCD agreed to act as team leader in undertaking the study (to include the City of Houston, TxDOT, and Harris County). In a letter to Harris County Commissioners Court seeking authorization for the study, HCFCD advised that the study plan would be based on a “recommended goal for communities in Harris County to reduce existing flood risk and to avoid increasing flood risks or creating new flood hazard areas,” and that “to help achieve the community goal, the purpose of the study would be to confirm or recommend updates to existing drainage policy, regulations, and design criteria based on technical analysis of the elements that make up an urban stormwater conveyance system,” and to “improve communication with the community regarding flooding and drainage issues.” CCFCC was invited and agreed to participate as a member of the Stakeholders Committee. The two million dollar, two-year study approved by Commissioners Court in September 2004 is significantly behind schedule.

US National Geodetic Survey (NGS): The National Geodetic Survey (NGS) defines and manages a national coordinate system. This network, the National Spatial Reference System (NSRS), provides the foundation for transportation and communication; mapping and charting; and a multitude of scientific and engineering applications (visit


Watershed: Also called a drainage basin, a watershed is the area in which water drains from higher to lower elevations of land coming together in bayous, creeks, and/or streams which, in turn, flow downhill into rivers eventually reaching the sea. There are twenty-one drainage basins in Harris County. Harris County land generally slopes downward until it meets sea level at Galveston Bay. Brays Bayou, Buffalo Bayou, Clear Creek, Spring Creek and Cypress Creek are some of the larger basins. For the most part, these basins flow from west to east. The highest level from which the water flows is called the “headwaters.” The point where the stream/creek/river ends by flowing into another body of water is called the “mouth.” Cypress Creek Watershed’s drainage begins in Waller County and gradually flows downhill to its mouth where it joins Spring Creek. This is part of a larger drainage basin called the West Fork of the San Jacinto, which flows into Galveston Bay (Note: Little Cypress Creek is a major sub-watershed of the larger Cypress Creek watershed and is often considered the “22nd Watershed” within Harris County by the HCFCD, although it is generally not categorized separately. It comprises more than 15% of the larger Cypress Creek watershed, with a drainage area of about fifty square miles).

Water Cycle: The water cycle describes the existence and movement of water on, in, and above the Earth. Water is always in movement and always changing states from liquid to vapor to ice and back again (visit

Watershed Environmental Baseline (WEB): A program developed by HCFCD to document/evaluate potential project alternatives (visit

Wetlands: Wetlands are areas where water is the primary factor controlling the environment and the associated plant and animal life. They occur where the water table is at or near the surface of the land, or where the land is covered by shallow water. There are more than fifty definitions of wetlands used throughout the world, but the broadest and most international is provided by the Ramsar Convention, which defines wetlands as “areas of marsh, fen, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters” (Article 1.1). Ramsar further incorporates into its consideration for listing “riparian and coastal zones adjacent to the wetlands and islands or bodies of marine water deeper than six meters at low tide lying within the wetlands” (Article 2.1). Ramsar categorizes wetlands into the following: estuaries, mangroves and tidal flats; floodplains and deltas; freshwater marshes; lakes; peatlands; and forested wetlands. This overview contains World Heritage natural and mixed sites, which qualify as Ramsar sites in addition to sites with significant inland wetlands (subterranean rivers and lakes), a coastal/marine component (coral reefs and islands), mangroves, and other sites with unique wetland and marine values (visit

West Harris County Regional Water Authority (WHCRWA): This is one of the two regional water authorities responsible for reduction of underground water withdrawal in order to prevent further land subsidence in the Cypress Creek Watershed. It generally encompasses watershed land south of U.S. Highway 290.

Wildlife: Many creatures live in the riparian corridors of the Cypress Creek Watershed. A primary objective of the CCFCC is preservation of the watershed’s wetlands, natural amenities, and aquatic and wildlife. CCFCC’s Greenway Project includes advocating for nature parks to preserve this important wildlife habitat along the thirty-seven mile main channel in addition to the development of numerous tributary trails and preserves where local residents can catch glimpses of beaver, blue heron, coyotes, ducks, egrets, owls, nutria, pileated woodpeckers and various species of turtles.

Thirty Key Concepts of the Clean Water Act (CWA):

Compiled in collaboration with River Network (visit
1. Reliable and accurate information about your watershed helps you use the Clean Water Act and all the other tools at your disposal. Much of the information you need has already been generated as a direct result of requirements of the Clean Water Act.
2. Point source discharges of pollutants to waters of the United States without permits are illegal. (A point source is any discharge of pollutants from a “discrete conveyance” such as a pipe).
3. National Pollutant Discharge Elimination System permits must impose discharge limits based on minimum performance standards or the quality of the receiving water, whichever type is more stringent in a given situation.
4. Minimum performance standards (called technology-based standards) are established by the EPA. They set minimum pollution control requirements for various categories of discharges, such as municipal sewage treatment plants and some industries.
5. Water quality-based permit discharge limits are established by the EPA or an agency to which the EPA has delegated authority. They must establish limits sufficient to protect the human and ecological uses of that particular water.
6. Permit violators are subject to fines of up to $25,000 per day (more in the case of repeated, negligent, or knowing violations).
7. If agencies fail to take appropriate enforcement action when permits are violated, individuals or public interest groups may sue violators directly to bring CWA compliance.
8. Public involvement during a permit period is critical. By providing information on the receiving waters, the public improves the effectiveness of permits.
9. Water quality standards established by states, districts, territories and tribes consist of three basic components: designated uses, water quality criteria, and anti-degradation requirements.
10. A state’s designated uses should include existing and desired uses of water that require good to excellent water quality. Water quality criteria may be site-specific. Citizens must make sure that the criteria for their watershed adequately protect designated and existing uses.
11. Water quality criteria establish standards for each designated use. They should consist of “numeric” and “narrative” descriptions of the chemical, physical, and biological water quality conditions necessary to support each of the designated uses.
12. Water quality criteria may be site-specific. Citizens must make sure that the criteria for their watershed adequately protect designated and existing uses.
13. The Clean Water Act’s anti-degradation requirements offer broad protection. Even if all other requirements are met, no activity that would compromise any one of the “three tiers” of anti-degradation is allowable.
14. Tier I of anti-degradation prohibits any activity that would remove an existing use.
15. Tier II of anti-degradation requires states to avoid, or at least hold to an absolute minimum, any lowering of quality of waters that currently meet or exceed standards.
16. Tier III of anti-degradation prohibits any activity that would degrade an “outstanding water” (a water body of exceptional ecological significance) or a water that has high recreational or other social value.
17. Mixing zones are areas designated where some or all water quality standards are waived to allow for dilution of pollution. Citizens should work to minimize their impact.
18. Changes to state water quality standards are to be considered at least every three years with at least one public hearing and opportunity for public review and written comment. This is the Triennial Review of Water Quality Standards.
19. Changes to state standards are not effective until approved by the EPA. If the EPA disapproves of a state’s water quality standards it must impose standards of its own.
20. In most states, citizens may serve as catalysts for consideration of specific changes to water quality standards through some type of state administrative process.
21. Impaired waters are waters that do not support designated uses after the application of the “National Pollutant Discharge Elimination System” permitting process and “best management practices” (mandated by the CWA). States must update their lists of impaired waters every two years after reviewing the best available data.
22. Total Maximum Daily Loads (TMDLs) are watershed-wide pollution budgets and associated clean-up plans. They are required for waters on a state’s impaired waters list.
23. Agencies must consider all available data, including data from the public, when listing impaired waters. They must also circulate a draft list every two years for public comment. Interested citizens should get involved in the development of Total Maximum Daily Loads (TMDLs) in their watershed.
24. All federal licenses and permits for activities which may result in any discharge into water require water quality certification under Section 401 of the Clean Water Act. This requirement gives states veto authority over federally permitted activities, and it is an opportunity to regulate activities on private land.
25. States may waive their water quality certification responsibility; it is automatically waived if the agency does not act on an application for certification within one year. The public should monitor Section 401 applications and draft certifications to prevent waivers if possible.
26. The Army Corps of Engineers regulates all proposed activities that will discharge dredged material into water such as dams, channel modifications to rivers and streams, or activities affecting wetlands. The EPA has veto authority over Corps “dredge and fill” permits.
27. The “dredge and fill” permits are a federal action; they require water quality certification from the state and endangered species consultation if applicable. It is one of the ways that private land activities are regulated.
28. Nonpoint source pollution reduction is funded through grants to states. States allocate the money thought grants and use some of the money to update state programs and nonpoint source assessments.
29. The Clean Water Action Plan, announced in 1998, calls for the nonpoint source program to stress a watershed-based approach to nonpoint source management.
30. State Revolving Water Pollution Control Funds (SRFs) are established in all fifty states. Used primarily for municipal sewage projects to date, these funds can be used for a wide variety of pollution control activities, including projects to address unregulated and difficult-to-find watershed problems.

NFIP Flood Risk Zones:
Moderate to Low Risk Areas:
Zones B, C, and X: Areas with less than a 1% chance of flooding each year; areas that have less than a 1% chance of sheet flow flooding with an average depth of less than one foot; areas that have less than a 1% chance of stream flooding where the contributing drainage area is less than one square mile; or areas protected from floods by levees. No base flood elevations or depths are shown within these zones.
High Risk Areas:
Zone A: Areas with a 1% annual chance of flooding and a 26% chance of flooding over the life of a 30-year mortgage. Because detailed analyses are not performed for such areas, no depths or base flood elevations are shown within these zones.
Zones AE and A1-A30: Areas with a 1% annual chance of flooding and a 26% chance of flooding over the life of a 30-year mortgage. In most instances, base flood elevations derived from detailed analyses are shown at selected intervals within these zones.
Zone AH: Areas with a 1% annual chance of shallow flooding, usually in the form of a pond, with an average depth ranging from one to three feet. These areas have a 26% chance of flooding over the life of a 30-year mortgage. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.
Zone AO: River or stream flood hazard areas, and areas with a 1% or greater chance of shallow flooding each year, usually in the form of sheet flow, with an average depth ranging from one to three feet. These areas have a 26% chance of flooding over the life of a 30-year mortgage. Average flood depths derived from detailed analyses are shown within these zones.
Zone AR: Areas with a temporarily increased flood risk due to the building or restoration of a flood control system (such as a levee or a dam). Mandatory flood insurance purchase requirements will apply, but rates will not exceed the rates for unnumbered A zones if the structure is built or restored in compliance with Zone AR floodplain management regulations.
Zone A99: Areas with a 1% annual chance of flooding that will be protected by a federal flood control system where construction has reached specified legal requirements. No depths or base flood elevations are shown within these zones.
High Risk – Coastal Areas: In communities that participate in the National Flood Insurance Program (NFIP), mandatory flood insurance purchase requirements apply to all V zones.
Zone V: Coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. These areas have a 26% chance of flooding over the life of a 30-year mortgage. No base flood elevations are shown within these zones.
Zone VE and V1 – 30: Coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. These areas have a 26% chance of flooding over the life of a 30-year mortgage. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.
Undetermined Risk Areas:
Zone D: An area with possible but undetermined flood hazards. No flood hazard analysis has been conducted. Flood insurance rates are commensurate with the uncertainty of the flood risk.