Addicks Reservoir Watershed
Updated November 2013
The Addicks Reservoir watershed is located in western Harris County with a small portion crossing into eastern Waller County.
Rainfall within the 138 square miles of the Addicks Reservoir watershed drains to the watershed’s primary waterway, Langham Creek
(U100-00-00). The Addicks Reservoir watershed occasionally receives a significant amount of natural stormwater overflow from the
Cypress Creek watershed during heavy rainfall events. Stormwater runoff from this watershed drains through the Addicks Reservoir
and eventually into Buffalo Bayou. Rural and agricultural uses have historically dominated the upstream regions of the watershed,
but residential and commercial developments are rapidly growing. There are 159 miles of open waterways in the Addicks Reservoir
watershed, including Langham Creek and its major tributaries, such as South Mayde Creek (U101-00-00), Bear Creek (U102-00-00)
and Horsepen Creek (U106-00-00). Based on the 2010 U.S. Census, the estimated population of the Addicks Reservoir watershed is
Together with Barker Reservoir, Addicks Reservoir was built in the 1940s as part of a federal project to reduce flooding risks
along Buffalo Bayou, which runs west to east through downtown Houston. The U.S. Army Corps of Engineers (the Corps) completed
construction of Addicks Dam and the outlet facility in 1948. The Corps owns, operates and maintains the reservoir, including
leases or permits for some compatible recreational uses within the basin. Operation of the outlet facilities controls discharges
from the reservoir into Langham Creek, then into Buffalo Bayou. Environmentally-sensitive areas and a wide range of wildlife
habitats exist within the reservoir boundaries and along the upper tributary reaches that extend into the Katy Prairie.
Active Capital Projects
Addicks Reservoir Watershed Model and Map Update - The Addicks Reservoir Watershed Model and Map Update study
is updating the hydrologic and hydraulic computer models for the Addicks Reservoir watershed that will result in revised Flood
Insurance Rate Maps (FIRMs or floodplain maps). Because of technological advances and additional studies, the Flood Control
District has an improved understanding of the amount and extent of the natural stormwater overflow from Cypress Creek into
Addicks. When this effort is complete, revised FIRMs for the Addicks Reservoir watershed will be produced based on
1-foot contour interval (rather than on 2-foot contour interval topographic maps) and based on 2008 Land Use data (rather
than on 2001 Land Use data). The draft revised FIRMs are under review by FEMA. This study also will produce other map products
as a result of the Harris County Flood Control District’s participation in a Federal Emergency Management Agency (FEMA) pilot
program called Risk MAP (Mapping, Assessment and Planning). This study will focus on the “Mapping” component of the Risk MAP
program. The maps will be made available to the public. Harris County is the first county in FEMA Region VI to participate in
the Risk MAP program.
Cypress Creek Overflow Management Plan - The Addicks Reservoir watershed occasionally receives a significant
amount of natural stormwater overflow from the upper Cypress Creek watershed during heavy rainfall events. To understand and
manage this overflow, a study has been initiated that will result in policies, technical criteria and guidelines to reduce
flood risks that are acceptable to area interests and reflect the unique hydrologic conditions in the area. The study area
includes upper Cypress Creek (upstream of Highway 290) and the drainage areas upstream of Addicks and Barker reservoirs,
including Langham Creek, Bear Creek and South Mayde Creek. Approximately 60 square miles of the upper Cypress Creek watershed
originate in Waller County and drain into Harris County. The Flood Control District and Harris County have received a grant
from the Texas Water Development Board to partially support this study effort. The first of three planned public meetings was
held in August 2012. Two additional public meetings will be held during the course of developing the plan. See
www.hcfcd.org/cypresscreekoverflow for further information.
Frontier Program - The Frontier Program is a way to accomplish an orderly drainage infrastructure in concert
with future land development. Working in partnership with landowners, the Frontier Program identifies strategies unique to
specific areas of the county that are distant from existing drainage infrastructure. These strategies will better mitigate
increased stormwater runoff, offer opportunities to provide community amenities through development of recreation and open
space areas, and enhance or preserve the area’s natural resources. Individual landowners and developers tend to adhere to
site-specific approaches to development that result in isolated detention basins and minimum-width channels for stormwater
management. In contrast to site-specific approaches, a regional plan facilitates construction of a channel corridor with wide
flood benches, gentle side-slopes, storage volume within the corridor cross-section for mitigation of floodplain and development
impact and outfall depth. The wider channel corridor in a regional approach allows for replacement of natural resource functions
that would be lost and habitats that would be inadequate in a piecemeal, site-specific approach.
In the past 20 years, the Harris County Flood Control District has spent nearly $12 million on capital projects in the Addicks Reservoir
watershed. The completed capital projects include channel improvements along Langham Creek and diversion channels on Bear, Langham and
Horsepen creeks. Active capital projects include implementation of concepts from the Frontier program and excavation of stormwater
Recently Completed Capital Projects
Upper Langham Creek Frontier Program - The purpose of the Upper Langham Creek Frontier Program is to implement
key elements – including right-of-way acquisition, pipeline adjustments, design and construction of control structures, and
environmental mitigation – of a regional drainage plan that embraces concepts from the Flood Control District’s Frontier
Program and uses funding from development impact fees. The plan includes a 700-foot-wide corridor for the stream and its
floodplain along with two detention basins. Excavation of the corridor and basins will be conducted by property owners –
primarily developers – as their properties are improved or developed. This project was authorized by the Harris County
Commissioners Court and will advance in phases.
Stormwater Detention Basin at John Paul's Landing Park - The Flood Control District is supporting Harris County
Precinct 3 efforts to develop a regional park and stormwater detention basin within John Paul’s Landing Park (U502-02-00),
which is located in the Upper Bear Creek and Upper Langham Creek area. While the Flood Control District completes a wetlands
mitigation project in support of this project, a portion of the stormwater detention basin has been excavated through an
excavation and removal agreement. Since 2011, the contractor has removed more than 1.1 million cubic yards of soil from this
site. A future capital project is planned to complete the first phase of the basin. The remainder of the basin volume will
be excavated on an as-needed basis by developers as a part of the Upper Langham Creek Program.
Site Improvements and Wetlands Construction - This project (K700-01-00-E001) will create and restore
approximately 95 acres of wetland habitat on the Katy Prairie near the intersection of Katy-Hockley and House Hahl roads.
The area provides required mitigation for other projects that will impact native wetlands, specifically the Greenhouse
Stormwater Detention Basin on Langham Creek (U100-00-00), northwest of the FM 529 and Barker-Cypress Road intersection
in the Addicks Reservoir watershed, and the John Paul’s Landing Stormwater Detention Basin on a Bear Creek tributary,
near the intersection of Katy-Hockley Cutoff and Sharp roads. The wetlands project, which included planting bog rush,
swamp smartweed, duck potato, powdered thalia and maidencane, began in 2013 and will cost approximately $203,000.
Routine and Completed Maintenance Projects
Upper Horsepen Creek Stormwater Detention Basin - In late 2012, the Flood Control District completed
the final phase of construction on this $1.36 million project (U506-05-00), located on a 175-acre site near the
intersection of Barker-Cypress and West roads in northwest Harris County. The final phase included construction
of a weir structure, which controls the timing and amount of stormwater that flows into a detention basin, and
significant re-grading of the detention basin’s slopes. During times of heavy rain, rising stormwater in Horsepen
Creek now flows into the basin via the weir and is temporarily stored until water levels drop. The basin has the
capacity to detain approximately 360 million gallons of stormwater and will help reduce flooding risks for those
who live downstream along Horsepen Creek. Harris County Precinct 3 is developing a county park at the basin, with
trails, playgrounds, a dog park, parking lots and other recreational facilities.
The Harris County Flood Control District oversees more than 2,500 miles (about the distance from Los Angeles to New York City) of bayous and
creeks and routinely performs maintenance projects to repair bayous and stormwater detention basins that have experienced erosion, slope
failure and sediment buildup. The Flood Control District also plants native grasses, wildflowers and trees to help reduce erosion and lower
mowing costs along bayous and stormwater detention basins in the Addicks Reservoir watershed.
Active Maintenance Projects
Mowing and vegetation maintenance - The Flood Control District performs routine cyclical maintenance, including
mowing of approximately 500 acres along bayous, creeks and stormwater detention basins in the Addicks Reservoir watershed. The
Flood Control District also performs selective clearing of invasive trees and vegetation.
Tree and wildflower plantings - Cedar elm, loblolly pine and red maple are just a few of the tree species that
were planted along two stormwater detention basins and a tributary identified as U119-00-00 in 2012. Along Langham Creek and
U119-00-00, the Flood Control District planted several species of wildflowers, such as clasping coneflower, drummond phlox,
Indian blanket and lance-leaf coreopsis in 2008 and 2011.
Horsepen Creek Maintenance Project - This maintenance project (U106-00-00-X024) removed accumulated sediment
along a 3.25-mile section of Horsepen Creek from State Highway 6 downstream to the Addicks Reservoir. The project addressed
spot erosion and pipe repairs along sections of the creek’s side slopes to help reduce the amount of eroded soil that falls
into Horsepen Creek. The project was completed in late 2012 at a cost of approximately $1.4 million.
Dinner Creek Channel Restoration Project - This project (U120-00-00-X007) will repair severe slope erosion and remove
sediment from a 4,800-foot section of this Langham Creek tributary, from Greenhouse Road to Freeman Road. Surveys have found sinkholes
and other examples of erosion, caused by overbank drainage and natural erosion due to poor soil quality. The project, which involves
replacing 25 damaged interceptor structures, installing riprap to armor the slopes, and removing sediment, is expected to be completed
Erosion Repairs in the Bear Creek watershed - This project, Z100-00-00-X190, will repair moderate to severe
erosion and remove sediment buildup in a section of Bear Creek (U102-00-00) between Greenhouse and Fry roads, and in a smaller
Bear Creek tributary (U102-25-00).