About MAAPnext

MAAPnext Project Overview

This project represents a transformative step in the management and regulation of Harris County’s floodplains, further contributing to our county’s resilience.

New methodologies and technologies will provide a better understanding of flood risks throughout Harris County.

The Harris County Modeling, Assessment and Awareness Project (MAAPnext) will develop the next generation of flood mapping. Along with new Flood Insurance Rate Maps (FIRMs), new tools will be developed for communicating the results of this project. Changes are on the way for Harris County flood maps, and we are ready to bring the region’s flood resistance and resilience to the next level.

WHAT ARE WE DOING?

The project will improve the understanding of the risk of flooding in Harris County so that the public, local communities and emergency managers can make informed decisions to protect life and property that may be at risk during flood events.

The Harris County Flood Control District and the Federal Emergency Management Agency (FEMA) are partnering on a flood hazard assessment project that will use the latest available technology and data to produce the county’s most comprehensive and complete set of flood hazard maps and information.

NEW METHODOLOGIES AND TECHNOLOGIES

Using new methodologies and technologies and the most granular data available, the Flood Control District will provide a better understanding of flood risks throughout Harris County, including previously unmapped urban flooding.

NEW DATA

Other new data and information that will be utilized include updated terrain data and improved hydrologic and hydraulic modeling technology and methods.

RESULTS THAT IMPACT FUTURE PLANNING

The Flood Control District expects many changes to be reflected in the resulting flood risk maps that will impact how future projects, new development, and their associated mitigation strategies are implemented.

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ATLAS 14

This assessment will incorporate the National Oceanic and Atmospheric Administration’s (NOAA) recently released Atlas 14 results, which included increased estimates to the total precipitation in standard return period events such as the “100-year.”

Interim Guidelines and Criteria for Atlas 14 Implementation

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WHAT DATA INFORMS MAAPNEXT?

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Impervious and Land Use Data Updated 2018

MAAPnext will use updated permeability data based on 2018 aerial imagery.

New 1D/2D Hydraulic Models

Up-to-date versions of the Hydrologic Modeling System and River Analysis System software products developed by the Hydrologic Engineering Center of the U.S. Army Corps Engineers now allows for feasible countywide 1D/2D analysis.

Topographic Data – LiDAR and Survey

Updated terrain data was obtained in 2018 and provides the foundation of hydraulics models and maps.

Public Outreach and Communication

If you have questions, concerns, or feedback related to MAAPnext, please visit the Get Involved. We look forward to working with you to deliver this significant project for our region and beyond!

Historical Storm Data and Atlas 14 Data

This assessment will incorporate updated rainfall depth, duration, and frequency data from the National Oceanic and Atmospheric Administration’s (NOAA) recently released Atlas 14, Volume 11 Precipitation-Frequency Atlas of the United States, Texas, and updated terrain data developed in 2018.

Completed flood damage reduction projects

In some cases, the Harris County Flood Control District may already be implementing a flood damage reduction strategy that will reduce flood risk for a given area. Data regarding completed flood damage reduction projects will be incorporated into MAAPnext.

WHY IS THIS PROJECT BEING DONE?

The MAAPnext project is being done to improve the understanding of the risk of flooding in Harris County so that the public, the District, our communities, and emergency managers can make more informed decisions to protect life and property against flooding.

MAAPnext aims to improve Harris County's flood risk toolkit by:

Using the latest estimates of rainfall risk to update our Flood Insurance Rate Map

Studying and mapping additional miles of streams to update our Flood Insurance Rate Map

Developing additional maps that will more thoroughly communicate flood risk

PROJECT RESULTS

Project results, including new hydrologic and hydraulic models, floodplain mapping, and other flood risk products will be delivered to FEMA for review by the second quarter of 2021. The project will conclude with the Flood Control District creating new flood hazard communications tools and FEMA releasing new preliminary Flood Insurance Rate Maps (FIRMs) by the end of 2023.

Flood Insurance Rate Maps (FIRMS)

A FIRM displays the floodplains—more explicitly, special hazard areas and risk premium zones—as delineated by FEMA.

A FIRM will generally show:

Roads and map land marks
Flood zones

Base flood elevations
Floodplain boundaries

Water surface elevation change grids

Representations of the difference between the effective and revised 1% annual chance floodplain water surface elevations.

Flood depth grids

Representations of the modeled water surface elevation for various flood frequencies, primarily the 10%, 4%, 2%, 1% and 0.2% annual chance flood events.

Urban Flooding Map

Representation of flood risk due to rainfall run-off draining through streets and neighborhood on the way to bayous.

Percent annual chance grids

Provide a better understanding of the relative probability of being flooded for any given location within the mapped floodplain.

Percent 30-year chance grids

Representation of the percent chance of a discrete location experiencing flooding at least one time during a 30-year period.

Water surface elevation grids

Representations of the modeled water surface elevation for various flood frequencies, primarily the 10%, 4%, 2%, 1% and 0.2% annual chance flood events.

These flood risk products will allow Harris County to understand flood risk by visualizing flood depths, flood water surface elevations, interpolated annual chance risk, and percent 30-year chance flood hazards.

MAAPNEXT PROJECT SCHEDULE

The MAAPnext effort will be completed in phases and will cover all of the county’s 22 major watersheds, all 34 local communities and unincorporated Harris County. The project will conclude with the Flood Control District creating new flood hazard communications tools and FEMA releasing new preliminary Flood Insurance Rate Maps (FIRMS) by the end of 2023.

Phase 1 Watersheds

Phase 1 consists of an hydrologic and hydraulic analysis of 11 of the County’s 22 watersheds. In early 2019, the Flood Control District received a grant from FEMA, which provided funding for this phase of analysis.

Phase 2 Watersheds

FEMA grant funding for the remaining 11 watersheds was received in late 2019, allowing the second phase of hydrologic and hydraulic analysis to begin in early 2020.

Flood Insurance Rate Map Update Timeline

MAAPNEXT PROJECT PARTNERS

MAAPnext is a collaboration that brings together national resources and local knowledge.

HARRIS COUNTY FLOOD CONTROL DISTRICT (HCFCD)

Since its inception in 1937, the Harris County Flood Control District has continually worked to better understand flood risk throughout the county. The Flood Control District's ongoing partnership with FEMA has led to MAAPnext, as well as the previous Tropical Storm Allison Recovery Project (TSARP), which resulted in new FEMA Flood Insurance Rate Maps for all of Harris County in 2007.

FEDERAL EMERGENCY MANAGEMENT AGENCY (FEMA)

The Flood Control District is participating in partnership with FEMA to deliver this effort, providing local matching funds and authorizing negotiations with expert engineering firms to support delivery of MAAPnext.

FLOODPLAIN ADMINISTRATORS

Throughout MAAPnext, the Flood Control District will work closely with the floodplain administrators within Harris County, all of whom have their own drainage design criteria. In unincorporated areas of Harris County, the County Engineer's office is the floodplain administrator. In all, there are 35 floodplain administrators in the county. (The Harris County Flood Control District is not one of them.)

HARRIS COUNTY RESIDENTS

The Flood Control District is committed to including Harris County residents throughout implementation of MAAPnext by implementing a consistent, continuous education program for the Harris County population to more easily understand and more clearly communicate about flood risks. If you would like to participate in the program, please contact us.

Harris County MAAPNext