About the Master Drainage Plan
The City of Friendswood is undertaking an ambitious effort to update its Master Drainage Plan (MDP)—a comprehensive, citywide study designed to identify drainage problems, recommend solutions, and guide future infrastructure investments. This plan builds upon previous phases completed in 1993 and 2007 and reflects the City’s commitment to flood resilience and responsible growth.
With support from the Federal Emergency Management Agency (FEMA) through the Hazard Mitigation Grant Program (HMGP), the updated MDP integrates modern technology, new flood modeling techniques, and recent data from regional initiatives to address both current vulnerabilities and future challenges.
The study will use advanced 1D/2D and 2D modeling to evaluate current vulnerabilities and test potential improvements under future rainfall scenarios.
What is a hydraulic model?
A hydraulic model is a mathematical model of a stream flow. These models are used to analyze stream behavior, such as flow direction, speed, and water volume. Hydraulic modeling for floodplain analysis generally falls into two categories: 1D and 2D modeling. And, the Friendswood MDP will incorporate both types of modeling into its analysis to develop the most comprehensive flood risk data available to date.
The type of modeling used to create the current FEMA effective floodplain maps assumes water moves just in one direction along a channel.
The type of modeling used as part of this study assumes water moves in multiple directions, both along a channel and between the channel and the overbank areas on each side.
By allowing water to move in multiple directions, the modeling provides a much more representative picture of how water flows and how areas drain. This is especially true for urban areas that are farther away from major channels and may drain via roadside ditches or storm sewer pipes.
MDP Benefits
The updated MDP will serve as a dynamic, data-driven roadmap to reduce flood risk and improve quality of life across Friendswood. Key benefits include:
- Actionable recommendations for small, medium, and large-scale flood mitigation and drainage improvements.
- GIS-based tools to support emergency response and responsible development decisions.
- Prioritized project list to help the City pursue additional funding and implement high-impact projects.
- Alignment with federal guidelines to ensure environmental compliance and access to external funding sources.
- Improved community awareness of flood risks through public outreach and engagement tools.
Goals of the MDP
The goals of the updated Master Drainage Plan are rooted in data, collaboration, and long-term sustainability:
- Assess areas of high flood risk under current and future conditions.
- Identify and prioritize feasible drainage projects.
- Enhance flood resilience through regionally coordinated planning and targeted local solutions.
- Support informed growth and infrastructure investment.
- Promote transparency and community engagement through outreach, meetings, and public input opportunities.
- Create a clear path to implementation, including funding and phasing strategies.
Study Area
The study area encompasses the entire City limits, covering 20.7 square miles and includes nine distinct sub-watersheds. Friendswood’s drainage is heavily influenced by Clear Creek and offsite flows from adjacent communities.
Study Partners
The Friendswood Master Drainage Plan is a collaborative effort made possible through federal, state, local, and technical partnerships.
Federal Emergency Management Agency (FEMA) – The study is funded in part through FEMA’s Hazard Mitigation Grant Program (HMGP), which supports long-term, cost-effective solutions to reduce the risk of natural disasters.
Texas Division of Emergency Management (TDEM) – Administers the HMGP grant on behalf of FEMA, serving as the pass-through agency for project oversight, compliance, and reimbursement.
City of Friendswood Engineering Department – Provides overall study oversight, facilitates local coordination, and ensures alignment with the City’s flood risk reduction goals.
Gauge Engineering – Serves as the Program Manager, overseeing regulatory compliance, offering managerial support, and conducting independent technical reviews.
Halff Associates – Acts as the Prime Consultant, responsible for managing day-to-day execution of the study scope, coordinating with City staff, managing subconsultants, and preparing the final study deliverables.
Technical Consultant Team – Includes Garver, Torres & Associates, Hollaway Environmental + Communications Services, and HTS Inc. Consultants. These firms provide specialized expertise in drainage engineering, environmental analysis, public engagement, and technical support throughout the study.
Together, these partners are developing a comprehensive and coordinated strategy for flood mitigation planning for the City of Friendswood.
Looking Ahead
Once complete, the updated Master Drainage Plan will equip Friendswood with the data, tools, and strategies needed to implement effective flood risk reduction projects. More importantly, it will reflect the voices and values of community, ensuring that the solutions developed today will continue to serve Friendswood for decades to come.
Visit the Get Involved page to learn how you can participate in shaping the future of flood mitigation in Friendswood.