Expert Drainage, Flood Control & Land Planning Blog | Tetra Land Services (Houston, TX)

Houston’s Flood Tunnel Debate: Size and Strategy Matter

Dwayne Culp, PhD., P.E., CFM.
October 8, 2025

As a Canadian-turned-Texan with nearly five decades in Houston, I’ve seen our city battle floods with grit and ingenuity. The esteemed Houston Chronicle recently questioned the undeniably brilliant Elon Musk’s claim that his Boring Company’s 12- foot-diameter tunnels, used in Nashville, could solve Houston’s flooding for a fraction of the Harris County Flood Control District’s (HCFCD) $4.6 billion, 36-foot-diameter tunnel plan. After crunching the numbers, I find Mr. Musk’s idea innovative but inadequate for Addicks Reservoir - though the tunnel’s untapped potential could fight both floods and subsidence.

The Real River State

Dwayne Culp, PhD., P.E., CFM.
August 1, 2025

Surface water fills Texas’ rivers, lakes, wetlands, and streams, directly exposed to environmental and human influences, making it prone to contamination from sediment, pathogens, and organic matter. Groundwater, stored in underground aquifers, is recharged by precipitation filtering through soil, a process that naturally reduces contaminants. All groundwater begins as surface water, undergoing filtration as it percolates. Globally, over 30% of freshwater resides in aquifers, 30% is locked in glaciers and permanently frozen sources, and 40% exists in surface water systems. Texas boasts an abundance of surface water, with fifteen named rivers, approximately 3,700 named streams, and roughly 80,000 miles of waterways, supporting diverse ecosystems and communities.

Miles from Venice

Dwayne Culp, PhD., P.E., CFM.
June 2, 2025

While I am originally from Canada, I’ve been in Houston for nearly five decades and consider myself a Texan. Frustratingly enough, in that time I have been unable to shake an old habit of reading foreign newspapers. In a recent perusal of the British press, I chanced upon a most disconcerting report proclaiming our cherished Houston as the swiftest subsiding metropolis in all of America. It was said that research from multiple sources have estimated “as much as 42% of Houston's land area is subsiding faster than 5 millimeters per year, and 12% is sinking faster than 10 millimeters per year.” Houston is indeed sinking, however we are miles from Venice, both figuratively and literally.

Eye of the Landholder

Dwayne Culp, PhD., P.E., CFM.
April 4, 2025

As beauty is in the eye of the beholder, expenses are different for every landholder. Land development engineering expenses vary for every landowner. The least expensive option is a detention facility draining via gravity to a public system, like a drainage ditch or storm sewer. In Harris County, detention rates depend on the outfall type. For an 8-foot outfall, 12-15% of the land is used for detention, while a 4-foot outfall requires 25-30%. Excavated material is often used to raise project elevations, including the detention facility's high bank. Adding one foot of detention can reduce land use by over 10%, a neat little trick for maximizing developable area.

Every Builder’s Concern

Dwayne Culp, PhD., P.E., CFM.
March 18, 2025

Harris County is in the process of issuing new flood maps based on Atlas 14 rainfall amounts showing an increase in rainfall by 20%. The net result is that for most buildings in the Houston area floodplains, the water surface elevations will be increasing. Every building owner needs to review the preliminary maps to determine how they impact the properties they own.

Down on the Bayou (Part 3)

Dwayne Culp, PhD., P.E., CFM.
March 12, 2025

As discussed in our previous column, for both commercial and residential development the City of Houston currently regulates minimum flood protection elevation of 0.2 percent flood elevation plus 2 feet. Harris County currently regulates minimum finished floor elevations to 0.2 percent flood elevation in areas where the drainage infrastructure meets the current design standards, and 0.2 percent flood elevation plus 2 feet in non-conforming subdivisions. Since elevation is a passive system, and requires no significant maintenance or manual intervention, elevation is generally the first option selected by engineers and architects for commercial systems. It is important to understand that commercial properties, unlike residential properties, have the additional option of floodproofing buildings to the same elevations as previously noted.

Down on the Bayou (Part 2)

Dwayne Culp, PhD., P.E., CFM.
November 16, 2024

Recall in the last article we discussed the need for floodplain regulations. In this article the discussion will be on how to develop in the floodplain. The most important concept to understand is the elevation known as Base Flood Elevation (BFE). The base flood elevation is the elevation of the water surface to which the city or county regulates development. In our region, the BFE could be the elevation of the stormwater during the 1%-event (100-year storm) or the 0.2%-event (500-year storm), dependent on jurisdiction.

Down on the Bayou (Part 1)

Dwayne Culp, PhD., P.E., CFM.
September 9, 2024

Regional developers are commonly challenged with developing low-lying land within the floodplain. Unlike stormwater regulations, which mostly defer to Harris County Flood Control Standards (HCFD), floodplain development regulations are unique to all 64 jurisdictions within Harris County alone. These regulations have been adopted by FEMA, and to participate within the National Flood Insurance Program (NFIP) these jurisdictions must have similar regulations, but not always similar interpretations. It can be confusing.

Green Solutions: A Guide to Low Impact Development

Dwayne Culp, PhD., P.E., CFM.
August 15, 2024

Low Impact Development (LID) attempts to mimic existing conditions in the developed world with regards to rainfall and stormwater runoff related design. LID techniques include: reducing pavement widths; reducing the amount of pavement in parking systems; increasing flow path lengths; adding filtration systems to the green areas; not directing stormwater to storm sewers; adding trees with large canopies to intercept stormwater and to enhance evapotranspiration; adding vegetation in unusual areas such as green roofs. Each of these systems has advantages and disadvantages, which we will review in brief.

Image credit: Elizabeth Conley, Houston Chronicle

Glenwood Cemetery

Josh van Nifterik
September 28, 2021

Latest update from our ongoing civil design work on a true Houston landmark, the oldest professionally designed cemetery in Houston; Glenwood Cemetery.

First River Oaks

Josh van Nifterik
September 24, 2021

Pre-design and feasibility still in the works for premium 17-acre site in River Oaks.

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Navigating Houston’s Terrain: Expert Drainage Solutions for Extreme Weather

Houston’s Flood Tunnel Debate: Size and Strategy Matter

The Real River State

Miles from Venice

Eye of the Landholder

Every Builder’s Concern

Down on the Bayou (Part 3)

Down on the Bayou (Part 2)

Down on the Bayou (Part 1)

Green Solutions: A Guide to Low Impact Development

Glenwood Cemetery

First River Oaks

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