Harris County Flood Control District

Leading the way for flood risk products, innovative solutions, and public-facing interactive mapping tools in southeastern Texas

Harris County Flood Control District (District) has been a member of the Federal Emergency Management Agency’s (FEMA) Cooperating Technical Partners (CTP) Program since 2000. This successful partnership resulted in the development of flood risk communication products, innovative solutions, and public-facing interactive mapping tools, promoting floodplain management, risk awareness, mitigation actions, and education while working toward a flood-resilient Harris County.

Out of hundreds of CTP partner agencies, the District has been selected by its peers as the 1st place recipient of the 4th annual Cooperating Technical Partners Recognition Program. This recognition is for the District’s ongoing efforts in the development of interactive mapping tools.

TSARP (2001-2007)

Map of 22 major watersheds in Harris County

Immediately following Tropical Storm Allison in 2001, the District launched the Tropical Storm Allison Recovery Project (TSARP) with a goal to model 1,200 miles of Harris County’s channels in 22 watersheds. The effort produced a new countywide set of high quality maps and models that became official in June 2007.

The TSARP effort included the creation of flood risk communication products that have guided community development decisions, increased understanding of riverine flood risks, and supported resilient floodplain management decisions.

Since 2007, the District has worked with FEMA to conduct several Risk Mapping, Assessment, and Planning (Risk MAP) studies to update the flood risk information where watershed-wide updates were required. These include Addicks, Sims Bayou, White Oak Bayou, Brays Bayou, and Hunting Bayou watersheds, usually due to large‑scale flood risk reduction projects or other factors.

M3 Program (2009)

In 2009, the District entered into an agreement with FEMA to become the custodian of the effective flood models for Harris County and established the Model and Map Management (M3) Program to assist in the effort of maintaining the quality models developed in TSARP.

The purposes of the M3 Program are:

  • To protect the investments in TSARP;
  • To ensure flood models and maps represent true, on-the-ground conditions; and 
  • To support resiliency efforts by providing accurate flood hazard information to FEMA and local communities.

Four Primary Objectives

1) Continuously manage and maintain an up-to-date model set

2) Establish and enforce local mapping and modeling standards through partnerships with floodplain administrators

Four Primary Objectives

3) Help coordinate concurrent development activities in watersheds

4) Provide a web application to distribute effective models and information

LOMR Review Partner (2010)

The District augmented its M3 Program by becoming a Letter of Map Revision (LOMR) Review Partner with FEMA in 2010. A LOMR is FEMA's official modification to a Flood Insurance Rate Map. LOMRs can change the regulatory floodway, the Base Flood Elevations, or the flood zones on the effective map. This partnership allows the District to process reviews of LOMR and Conditional LOMR submittals in Harris County.

Through the LOMR Review Partnership, the District was able to provide value by:

  • Applying local knowledge of area issues and projects;
  • Meeting in person with requestors;
  • Facilitating the coordination of adjacent active cases; and
  • Reducing overall review time.

FEMT (2011)

Purpose: The District developed the Flood Education Mapping Tool (FEMT) in 2011 to present floodplain information to the public in a user-friendly way. 

Ease of Use: By just using an address in Harris County, one can identify the corresponding watershed and explore the extent of the mapped floodplains in that vicinity.

Return on Investment

Sample Heat Map: Memorial Day 2015, 6-Hour Duration The heat maps we generate from gauge data for various durations tell the story of rainfall intensity across our communities after major floods.

The M3 Program maintains quality engineering models which can be used to evaluate the potential impacts of proposed projects. These models can also be modified to reflect pre-project conditions (or pre-project models may already exist). Pre-project models can be used after real flood events to estimate how much flooding was avoided thanks to the District’s flood reduction projects. 

Quantifying the benefit of these projects helps illustrate the return on investment in flood reduction projects to the public, elected officials, and potential funding partners.

The District takes rainfall records from real flood events and inputs them into pre-project models. Those model results are compared with the actual flood outcomes to determine the reduction in flooding severity as a result of implemented structural and non-structural flood reduction measures. The District has estimated avoided losses for major floods since the Memorial Day 2015 event.

Since 2015, the benefits of structural (construction projects) and non-structural (buyout) efforts by the District have added up to over 44,400 prevented instances of flooding (Imelda estimates included).

In watersheds like Sims, Brays, and White Oak Bayous where regional projects have improved channel capacity, the flood risk has been significantly reduced, resulting in a sizable return on investment from one storm event to the next.

FIMT-RT (2018)

In March 2017, the District initiated the Real Time Flood Inundation Mapping Tool (FIMT-RT). The tool was tested during Hurricane Harvey in August 2017 and launched on the District’s Flood Warning System (FWS) website in June 2018.

Based on real-time water level readings from area gauges and information from engineering models, the tool estimates water levels along the length of gauged streams and maps the extent of flooding along those streams.

The mapped extents are displayed on the FWS website on a near real-time basis.

HCFCD is in the process of developing a flood forecasting tool based on the District's effective models developed during TSARP and maintained through the M3 Program.

New LiDAR (2018)

Light Detection and Ranging (LiDAR) is a surveying method that measures distance to a target by scanning an area with a laser and measuring how long it takes the light to return to a sensor. The District acquired high quality, high resolution LiDAR ground elevation data for the entirety of 22 Harris County watersheds.

The digital elevation model generated from the LiDAR with a cell size 3 feet by 3 feet allows for detailed hydrologic and hydraulic modeling which now serves as the basis of the ongoing Modeling, Assessment, and Awareness Project (MAAPnext) to update the county’s flood risk and update the flood risk communication products.

MAAPnext (2019)

In April 2019, the District began MAAPnext, a project to improve our understanding of flood risk in Harris County. MAAPnext uses rainfall information from the 2018 National Oceanic and Atmospheric Administration (NOAA) Atlas 14 study, the newly acquired 2018 LiDAR, and modernized modeling techniques. NOAA Atlas 14 contains the latest rainfall data for much of the United States, and generally replaces the older published data. 

MAAPnext will yield flood risk products that better describe the flooding conditions in Harris County, including two-dimensional modeling capability that show how floodwaters move across a flat terrain after channels exceed their capacity. These products will also help us illustrate and describe the county’s urban flood risk.

1D Modeling (TSARP) looks at a stream as a series of slices (cross sections) perpendicular to the direction of flow. 1D models can be built with less detailed data but rely on certain assumptions of how water flows into and through the modeled system. 2D Modeling (MAAPnext) considers the way water flows over detailed terrain. 2D models avoid many of the assumptions of their 1D counterparts and, as a result, provide a more accurate representation of the complex hydraulic conditions encountered in Harris County.

Special Projects

The District partnered with FEMA on a flood risk and insurance billboard campaign in 2019. The campaign relayed flood risk and flood insurance information to Harris County communities through 12 billboards with messaging in English and in Spanish.

The billboards were placed at 12 high traffic locations off main highways to direct onlookers to the District’s website that provides information about flood risk and flood insurance. Learn more at  https://www.hcfcd.org/floodinsurance .

Hurricane Season: June to November Flood Season: Year-Round

Floods can happen at any time, and you do not have to live in the 100-year floodplain to be at risk of flooding. In fact, many flood loss claims in Harris County are located outside of the mapped 100-year floodplain.

The District recommends that all Harris County residents become informed about their flood risk and have flood insurance no matter where they reside in Harris County.

Projects will continue in 2020 and 2021 to develop additional educational tools and means of informing local communities about flood risk and ongoing MAAPnext project developments.

The District’s decades-long relationship with FEMA has provided mutually beneficial outcomes and provided professionals and residents within Harris County access to expertise, data, and educational opportunities to promote floodplain management, risk awareness, and resilience. 

CTP Overview

The CTP Program enhances partnerships between FEMA and eligible entities. FEMA teams with these partners to deliver high-quality hazard identification and risk assessments, provide outreach support, and help empower communities to bring more awareness and take action to reduce their risk through the latest data and resources.

Hurricane Season: June to November Flood Season: Year-Round

Map of 22 major watersheds in Harris County

Sample Heat Map: Memorial Day 2015, 6-Hour Duration The heat maps we generate from gauge data for various durations tell the story of rainfall intensity across our communities after major floods.

The District takes rainfall records from real flood events and inputs them into pre-project models. Those model results are compared with the actual flood outcomes to determine the reduction in flooding severity as a result of implemented structural and non-structural flood reduction measures. The District has estimated avoided losses for major floods since the Memorial Day 2015 event.

In watersheds like Sims, Brays, and White Oak Bayous where regional projects have improved channel capacity, the flood risk has been significantly reduced, resulting in a sizable return on investment from one storm event to the next.

1D Modeling (TSARP) looks at a stream as a series of slices (cross sections) perpendicular to the direction of flow. 1D models can be built with less detailed data but rely on certain assumptions of how water flows into and through the modeled system. 2D Modeling (MAAPnext) considers the way water flows over detailed terrain. 2D models avoid many of the assumptions of their 1D counterparts and, as a result, provide a more accurate representation of the complex hydraulic conditions encountered in Harris County.