Hurricane Harvey

As of 08/19/2019

C-17 San Jacinto Regional Watershed Master Drainage Plan


The San Jacinto Regional Watershed Master Drainage Plan (SJMDP) is a comprehensive regional study funded by a federal grant and local partnershipsThe SJMDP study effort is led by the Harris County Flood Control District (HCFCD), joined by three other local agencies: the San Jacinto River Authority (SJRA), Montgomery County, and the City of Houston.

> Study Timeline

The SJMDP website is going live in August of 2019, please check back soon!


This map shows the web of creeks and their tributaries that drain into the upper/northern portion of the San Jacinto River and reflects the limits of the current MDP study boundary which ends just downstream of I-10. 

> Enlarge Map

The nearly 3,000 square mile study boundary includes parts of Harris, Montgomery, Waller, Grimes, Walker, Liberty and San Jacinto counties. Creeks and bayous in this watershed include Spring Creek, Cypress Creek, Little Cypress Creek, Luce Bayou, Willow Creek and Jackson Bayou. Municipalities and communities in the watershed include Kingwood, Conroe, Tomball, The Woodlands, and part of Huntsville.

> Questions or Comments about this project? (and join mailing list)

A total of 535.6 stream miles of the major creeks and rivers within the MDP study boundary are being analyzed and/or updated with current Atlas 14 rainfall data and newly available aerial imagery and terrain data. 

> Enlarge Map

The blue lines in this map represent the major streams being studied in this MDP effort.   

This integrated effort, kick started in April 2019 upon receipt of the federal grant, identifies future flood mitigation projects that can be implemented in the near- and long-term to reduce flood risks to people and property throughout the San Jacinto River regional watershed

> San Jacinto Master Plan Summary - Fact Sheet (May 2019)

The HMGP application timeline for this project shows the funding process as required by the Federal Emergency Management Agency's Hazard Mitigation Grant Program (HMGP) administered through the Texas Division of Emergency Management (TDEM) - a part of the Texas Department of Public Safety.

About the Study

The goals of the San Jacinto Regional Watershed Master Drainage Plan are to:

  • Identify the region’s vulnerabilities to flood hazards using Atlas 14 rainfall
  • Develop approaches to enhance public information and flood level assessment capabilities during a flood disaster event
  • Evaluate flood mitigation strategies to improve community resilience
  • Provide a comprehensive Flood Mitigation Plan that supports the needs and objectives of each regional partner

A set of hydrologic and hydraulic models are being developed using consistent, cohesive methodology and rainfall rates, regardless of the county in which those channels are located.

What is hydrologic and hydraulic analysis and modeling?

Using hydrologic and hydraulic data from the U.S. Geological Survey, FEMA, and organizations like the Flood Control District, engineers are able to utilize an integrated system of software to simulate real‑world conditions in our region’s bayous, streams, and channels. These simulations are completed using hydrologic and hydraulic, or H&H, models.  These models predict how precipitation will impact the landscape with estimates of how deep the water will get at different locations and how frequently this water depth will occur under certain weather conditions. Other models are used to estimate the monetary damages that can be expected when these events occur in developed areas and damage property.

> VIDEO: H&H Analysis and Modeling

The product from this MDP study will include non-regulatory inundation maps (not intended to replace current effective maps) for the studied/analyzed streams that show the extent and depth of riverine flooding of the larger rivers within the watershed for an array of simulated storm events. Additionally, information will be available on the number of structures, acres of land, properties, and miles of roadway that are located within the modeled inundation areas. These results will be available to inform and update Hazard Mitigation Plans for not only the participating partners, but all communities and jurisdictions located within the MDP study boundary, also to provide guidance on regulations for future growth within the watershed.

Anticipated Schedule

  • Existing hydrology and hydraulics analysis and calibration complete – Fall 2019
  • Primary alternatives analysis complete – Winter 2019
  • Vegetation and sediment control analysis complete – January 2020
  • Draft report complete – Summer 2020
  • Final report complete – Fall 2020

Recent Action

July 30, 2019 – Harris County Commissioners Court authorized negotiations with Woodlands Municipal Utility District  No. 1; Montgomery County Municipal Utility District Nos. 7, 46 and 60; and Harris-Montgomery Counties Municipal Utility District No. 386 for a partnership project to evaluate the feasibility of reservoirs in the Spring Creek Watershed to reduce flood risks on the San Jacinto River, HCFCD Unit G103-00-00, and Spring Creek, HCFCD Unit J100-00-00

March 12, 2019 – Harris County Commissioners Court approved a $2.71 million agreement with an engineering firm to conduct this watershed study

February 12, 2019 – Harris County Commissioners Court approved acceptance of a $2.03 million grant from the Federal emergency Management Agency, with a $677,052 required Flood Control District match

February 12, 2019 – Harris County Commissioners Court approved a $203,116 agreement with Montgomery County, the San Jacinto River Authority and the City of Houston in support of this study

September 25, 2018 -- Harris County Commissioners Court authorized a grant application to the Federal Emergency Management Agency in support of this project