A popular misperception says Halls Bayou has received no flood-mitigation funding. Yet it has received $175 million since 2000. $65 million of that happened since Harvey.

Channel widening, stormwater-detention basins and neighborhood drainage improvements have reduced flood risk somewhat, but several factors – including the need for more funding – make mitigation difficult. HCFCD has many projects still seeking federal assistance.

The Bond Program approved by voters in 2018 includes more than $110 million for the Halls Bayou watershed. That money could help attract another $236 million in federal matching grants for a total of $346 million. But many projects have yet to receive grants and start construction.

Halls cuts diagonally across the northern part of Harris County between Beltway 8 and Loop 610 North. It joins Greens Bayou before the Ship Channel.

Background: Halls Ahead

Halls received an extraordinary amount of damage during Tropical Storm Allison in 2001. Among all 23 Harris County watersheds, it ranked second only behind Greens Bayou during that storm. But Greens has four times the area and three times the population. (Greens had 15,590 damaged structures; Halls had 12,820.)

As a result, HCFCD launched many studies of Halls drainage after Allison. They culminated in the 2013 Halls Ahead Plan. But HCFCD lacked money to fully implement it and still does. All unfunded Halls Ahead projects carried forward into the 2018 Bond Program and many were able to start as you will see in the pictures below. Several have even finished. However…

A Phasing Study designated 58 flood risk reduction projects in 12 phases, with estimated costs between $100 million and $150 million per phase. 

Flood Control executives recently traveled to Washington to plead for more help from the Army Corps of Engineers. The Corps now has a pilot program to help economically disadvantaged areas and Halls certainly qualifies. Halls has the highest percentage of vulnerable, Low-to-Moderate Income (LMI) residents of any watershed in Harris County (71%).

Complicating Factors

Halls is plagued by a combination of factors that make flood mitigation difficult:

• Silted-in roadside ditches
• Aging stormwater infrastructure
• Developments built to older standards
• Homes frequently built at street level
• Dense population that leaves little room for mitigation projects
• Structures built in floodplains that have to be bought out before many mitigation can begin (see below).

Flood History in Halls Watershed

Much of the Halls Bayou watershed developed during or after the 1950s. Take this area immediately east of what became I-45. It was farmland before then.

Homes and businesses built in Halls Bayou floodplains created the flood risk. They also make widening channels or building detention basins difficult because of time-consuming, expensive buyouts.

Vital Stats

These statistics help put Halls Bayou flood problems in perspective. Here’s how Halls ranks among 23 Harris County watersheds on:

• Watershed size – #16 (42.3 square miles)
• Population – #10 (152,358 in 2020 census, down 5% from 2010)
• Population density – #6 (3,602 people/square mile)
• Dollars per capita in flood mitigation spending – #5 ($1151 per resident)
• Dollars per square mile – #4 ($3.9 million dollars per square mile between 2000 and the end of last year).
• Damaged structures – #4 (25,691 structures during five major storms since 2000 [Allison, Tax Day, Memorial Day, Harvey and Imelda])
• Damage per square mile – #1 (607.4 structures/sq. mi.)

That last point makes recovery difficult for communities, especially less affluent ones. It may help explain the decrease in population.

Allison, Harvey Dramatize Need for Mitigation

HCFCD has documented flooding along Halls 14 times since 1989. But the two worst storms were Allison (2001) and Harvey (2017). Allison damaged 12,820 structures in the watershed. But Harvey damaged fewer – 11,831.

It’s fairly safe to say that without many mitigation improvements made prior to Harvey, Harvey damage would have been worse. However, rainfall distribution patterns make comparisons between the storms difficult.

The following table from HCFCD’s final Harvey report compares rainfall associated with severe, recent storms for various time periods. Tropical Storm Allison exceeds Harvey’s rainfall in the 6, 12 and 24-hr periods. But in the 2-day period, Harvey produced 6.0 inches more than Allison and 8.9 inches more over 4 days.

Photos of Stormwater Detention Projects from 7/19/22 Flyover

Last Tuesday, I flew most of the length of Halls Bayou with two fellow members of the Harris County Community Flood Resilience Task Force, Ken Williams and Bill Callegari. Let’s take a look at several Halls projects already completed or under construction – starting upstream and working east.

Helms Street Basins

East Helms runs between these two small basins just south of Aldine Mail Route Road. HCFCD completed these last year. They hold 119 acre-feet. That’s a little less than 3″ of stormwater falling over a square mile.

P518-11-00

I last reported on this project in March 2022. It’s still under construction.

The $6 million stormwater detention basin project will provide regional mitigation benefits. 

The basin will hold 180 acre-feet of stormwater. That’s about 3.5 inches of rain falling across a square mile. It will be a wet-bottom basin with a vegetated shelf.

This basin is part of a larger mitigation project that will also extend and enlarge a channel north to the Western Homes subdivision along Aldine Mail Route Road.

Keith Weiss Park

One of the hidden gems of Houston is Keith Weiss Park east of Aldine-Westfield Road. The area is really a series of large connected detention basins disguised as a nature park with hike and bike trails, soccer fields, piers and boardwalks. City of Houston owns the park.

The Keith Weiss project removed 1,770,000 cubic yards of soil to create detention basins that hold approximately 963 acre feet of stormwater storage. That’s enough to hold a foot of stormwater falling across 1.5 square miles.

Google Earth shows that excavation started around 2006 and was substantially completed by 2010.

Channel Improvements

HCFCD is making channel improvements along Halls in many locations. See project C-41. The area below lies between Keith Weiss Park and US59.

Bretshire Stormwater Detention Basin

The Bretshire Stormwater Detention Basin on Halls Bayou added approximately 635 acre feet of additional stormwater storage upstream of Jensen Drive at US 59. It holds a foot of stormwater falling across one square mile.

A large part of a subdivision had to be bought out before construction of this basin could begin. HCFCD substantially completed this basin in 2015.

Hall Park Basin

HCFCD also had to buy out a large part of a subdivision to build the Hall Park basin on the opposite side of US 59. Flood Control substantially completed this project in 2018.

Hall Park holds 835 acre-feet. That’s enough to hold a foot of water falling across 1.3 square miles.

This project involved relocating a City of Houston sanitary sewer line and removing approximately 1.2 million cubic yards of soil.

As part of its Bayou Greenways 2020 project, the nonprofit Houston Parks Board is designing and constructing the Halls Bayou Greenway – which includes a hike and bike trail, landscaping and neighborhood connections – along the southern edge of the stormwater detention basin. The full Halls Bayou Greenway will provide nine miles of publicly accessible open space from Brock Park to Keith Wiess Park.

In many cases, such stormwater detention basins are disguised as parks. So, many people don’t even recognize them as basins.

Hopper and Little York Basins

Slightly east of 59 at Hopper and Little York, HCFCD constructed two smaller basins in 2021 along a tributary of Halls. Together they hold approximately 200 acre feet. That’s about a foot of rain falling over a third of a square mile. Or four inches across a whole square mile.

Such projects hold water back during storms until it can be slowly and safely released later when water in the bayou has receded.

Holding Back A Foot of Rain Falling Across Almost 5 Square Miles

Altogether, the detention basins in this post will hold almost a foot of stormwater falling across 5-square miles.

Halls Bayou has many other projects in various stages. For a complete listing, see the HCFCD website. Or review this presentation.

Posted by Bob Rehak on 7/23/2022

1790 Days since Hurricane Harvey