Chris Bloch Archives - Reduce Flooding

Sinkholes Often Sign of Damaged Storm Drains

Most of us have seen sinkholes. And most of us have probably given little thought to what causes them.

Retired engineer Chris Bloch, a local flood fighter, measured a 13-foot deep sinkhole near Taylor Gulley earlier this year that had become overgrown with vegetation. Working with the City of Houston and a local homeowner who first reported the problem, they found the sinkhole related to a nearby storm drain.

*Bloch lowered this length of PVC pipe into the Taylor Gully sinkhole to measure the depth.* *Note how the hole had become overgrown with vegetation.*

Other things can cause sinkholes, but in this area and in this part of the world, “storm drain gone bad” ranks high on the list of things to investigate.

Corrugated Pipe Commonly Used At Outfalls When Kingwood Built

According to Bloch, when Friendswood built Kingwood, they commonly used corrugated metal pipe (CMP) at storm sewer outfalls. CMP has an expected service life of approximately 35 years, says Bloch. And corrosion commonly causes failure at older outfalls constructed with such pipe.

For example, see the section of pipe below. This photo was taken on Ben’s Branch, not Taylor Gully, but it shows how the pipe rusted, bent, and crimped. Also look just to the right of the wooden posts, and you can even see a large hole in the pipe. It even tilts upward before it reaches the creek.

Corrugated metal pipe replaced earlier this year as part of a project to restore the conveyance of Bens Branch between Rocky Woods and Kingwood Drive. This area also developed a sinkhole near the manhole.

Taylor Gully Sinkhole One of Many In Area

Bloch frequently walks ditches looking for sinkholes to report to the City. He says he’s aware of at least five right now.

The 72-inch outfall to Taylor Gully serviced drainage area G03408-00-OUT which encompasses all of Greenriver Valley Drive and Mountain Bluff Lane as well as portions of Appalachian Trail, Natural Bridge and Echo Falls Drives. That area comprises 33.4 acres. See below.

*Service area for damaged outfall encompasses 33.4 acres where several homes flooded.*

The transition from a 72-inch concrete storm sewer to the 72-inch CMP outfall is at a manhole on the edge of the Taylor Gully right of way. See below.

Over the years, the CMP at the connection to the manhole failed. The earth above the failed pipe washed into the outfall and then downstream where it helped reduce the conveyance of Taylor Gully.

Repairs Started But Not Complete

The City of Houston has already repaired several storm sewers with failed corrugated metal outfalls. At least five additional storm sewer outfalls with sinkholes have been identified that have not yet been repaired.

Vegetation frequently hides the presence of these sinkholes. In addition to posing a danger to citizens walking along the banks of the drainage channels, the soil that falls into the sewer can be held up by the corrugations of the metal pipe reducing the flow capacity of the sewer, says Bloch.

Even without obstruction from soil falling into a sewer outfall, the rough surface of the corrugated metal pipe generates greater friction than smooth concrete. The friction slows the flow of storm water and reduces flow capacity which becomes critical during high intensity rains that cause street flooding.

Bloch somehow convinced the City of Houston Public Works Department to replace the damaged CMP at Taylor Gully with concrete pipe. See below.

“This upgrade in the outfall piping will significantly improve the flow capacity of the storm sewer system,” says Bloch.

*Concrete pipe replaced CMP at the location of the 13-foot sinkhole on Taylor Gully. Installed by City of Houston Public Works Department* *after HCFCD repaired Gully.*

Concrete Better for New Atlas-14 Rainfall Intensities

When Friendswood Development installed stormwater sewers in Kingwood, they met standards which applied at that time. With new Atlas-14 rainfall projections, we now understand that we should expect more rainfall. Several homes along Appalachian Trial suffered flood damage during Tropical Storm Imelda.

How to Report Sinkholes When You Find Them

As they say, it takes a village to reduce flooding. Now that you know the story behind sinkholes…

If you jog or walk along drainage ditches, exercise caution. Look out for developing sinkholes. And report them to 3-1-1 when you find them. They can pose dangers to children and even grown adults. To put that in perspective, Bloch (shown in the first photo) is more than 6 feet tall, but the sinkhole dwarfs him.

For More Information about Sinkholes

I highly recommend:

The US Geological Survey has an in-depth discussion of different types of sinkholes in different parts of the country and how each forms. This is geared toward students in science classes.

This NBC News story on YouTube has some spectacular examples of sinkholes in Florida along with easy to understand animations that show how they form.

Another 7 minute YouTube video from a series called Practical Engineering focuses on how sinkholes form. It contains both real world examples and table-top experiments that bring the processes to life.

Posted by Bob Rehak based on information and photos provided by Chris Bloch

1492 Days since Hurricane Harvey

City Repairing Storm Sewer Outfalls

One of the most often overlooked points of failure in drainage systems is the lowly storm sewer outfall. When rain flows into the storm sewer on your street, it travels through pipes underground until it reaches the “outfall” at a stream or drainage ditch. If the outfall becomes blocked or damaged, it can back water up and contribute to street flooding.

Often, the damage to the outfall is so remote and difficult to find, that unless someone makes it his or her specific mission, it can go undetected.

Chris Bloch Takes on the Mission

Luckily for Kingwood residents, retired engineer Chris Bloch has made it his mission to identify damaged outfalls and bring them to the attention of the City of Houston. In his quest to help the Kingwood community, Bloch has trudged through mud, muck, brambles and underbrush for years. But his persistence has finally started paying dividends.

Recently the City repaired four outfalls that empty into Bens Branch. The repairs coincided with Harris County Flood Control District’s project to restore conveyance of the channel between Rocky Woods and Kingwood Drive. The result: reduced flood risk to surrounding neighborhoods.

*Locations of four outfalls recently repaired by City of Houston in conjunction with HCFCD restoration of Bens Branch*

Below: pictures before and after the repairs.

Outfall #1: Cedar Knolls At Woods Estates

*Outfall #1 before repairs. Severe erosion exposed then partially severed pipe.* *The erosion resulted from churning water behind a logjam in the natural section of Bens Branch.*

*The logjam that created the erosion has since been removed* *by HCFCD.*

*Outfall #1 drained approximately 10.7 acres.*

The outfall repaired by the City was upstream of HCFCD’s Ben’s Branch restoration project. Of the two other outfalls in this photo, HCFCD repaired the one in the foreground and the City repaired the one in the middle. See Outfall #4 for more info on that one.

Outfall #2: Laurel Garden and Bens Branch

*At point #2, drain pipe had cracked and was pushed upward, causing water to back up.*

A sinkhole also developed along this line. That usually results from part of the pipe collapsing in on itself. Dirt above the hole then erodes into the pipe. The City plans to address the sinkhole now that Flood Control has finished its work.

Outfall #3: Wildwood Ridge Near Deerbrook

According to Bloch, this area originally had 22 feet of corrugated metal pipe and another 50 feet of concrete pipe sections that failed. Erosion undercut the pipe and washed it away.

As erosion widened and deepened the area around the destroyed pipe and a manhole, trees fell into the widening “ditch.” The blockages caused the water to churn, creating even more erosion.

Below is the “after” shot. Instead of replacing all the pipe, the City created a wider ditch that will greatly improve street drainage in this watershed.

*The area eroded by the damage to outfall #3 has been replaced by a side ditch. It will provide more than enough conveyance to handle water exiting the 36″ pipe.*

In the picture above, the rocks surrounding the outfall are called riprap. Riprap is a permanent layer of large, angular stone, cobbles, or boulders typically. Riprap armors, stabilizes, and protects the soil surface against erosion and scour in areas of concentrated flow, such as at outfalls.

*The storm sewer outfall #3 services a drainage area of 28.6 acres.*

Outfall #4: East Side of Bens Branch at Rocky Woods and Wildwood Ridge

During a storm, the cover on this manhole blew off. Later, young people threw wood into the open manhole and started fires while they drank beer.

*Before repairs.* *The manhole acted as a chimney that made it easy to have a roaring fire.*

*People also threw beer cans and other debris into the manhole.*

Eventually the sewer line became completely blocked according to the City. As a result, storm water backed further up the line. Increased pressure lifted covers off of all upstream manholes. In addition, the pressure forced storm water out between the concrete pipe joints and created a number of sinkholes.

Due to all of this damage approximately 580 feet of 24-inch sewer line and three manholes had to be replaced by the City. This is probably one of the most expensive cases of vandalism Kingwood has experienced.
Chris Bloch

With the line completely blocked, it was of no use and storm water runoff from this area would flow further down Wildwood Ridge where several homes suffered flood damage.

*Outfall #4 after repairs. Note also replacement of the manhole.* *Not shown: the 580 feet of other repairs including more manholes.*

*The drainage area serviced by this sewer is only 5.6 acres, the 24-inch line was more than adequate for this acreage.*

Kudos to the City and Bloch

These are just four of several repairs underway. More news to follow.

Thanks to the City of Houston, Mayor Pro Tem and District E Council Member Dave Martin, and his staff for coordinating these repairs with the Public Works Department. Residents will sleep much better in the next big storm.

Thanks also to Chris Bloch for his tireless efforts in reporting these issues. If you find similar problems near your home or business, please report them through the contact page on this web site. I’ll make sure they get to Chris who will make sure they get to the people who can help.

Posted by Bob Rehak on 4/18/2021 based on information and photos collected by Chris Bloch

1328 Days since Hurricane Harvey

City Quietly Cleaning Out Culverts Under Kingwood Drive Thanks to Local Activist

Chris Bloch, an engineer and Kingwood resident, has become a flood-control activist in his retirement. I often run into Chris inspecting ditches, streams and culverts for blockages and collapsed outfalls. Chris also works with the Bear Branch Trail Association which owns property along many of the channels and streams cutting through Kings Forest, Bear Branch, and Hunters Ridge.

Activist Extraordinaire

For the last several months, Chris has focused intensely on blocked channels that contributed to the flooding of 110 homes in Kings Forest during Harvey. Where the channels cross under Kingwood Drive, three had become almost totally blocked by vegetation and silt. That contributed to backing water up into homes. See below.

*Ditch at Shady Run and Kingwood Drive before clean-out.* *Photo courtesy of Chris Bloch.*

Chris meticulously photographed the problems, began researching which entities were responsible for which portions of the channels, and in the case above, contacted the City of Houston. The City has responsibility for the medians and sides of Kingwood Drive and other streets. His persistence paid off.

In October, the City began cleaning out the ditch near Shady Run and Kingwood Drive.

*Vacuum truck photographed at same location on 10/3/2020*

Here’s what that part of the channel looks like today.

*Same ditch after clean-out*. *Photo courtesy of Chris Bloch.*

End-to-End Inspections

Chris is tenacious, tireless, and wide ranging. He looks at ditches from end to end. In this case, he’s also trying to get the Flood Control District to escalate clean-out of the ditch south of Kingwood Drive. Reduced conveyance through that reach could also have contributed to flooding in Kingwood Lakes.

Bloch says he has also identified twenty storm-drain outfalls that need repair. “It doesn’t make any difference if the storm sewers are clear if the water in them can’t get to ditches and streams,” he says.

You Be an Activist, Too

Activists like Chris make Kingwood the great place it is. They help identify local problems for government and make the case for addressing them.

As you hike through our greenbelts and along channels, keep your eyes open for developing problems:

Collapsed outfalls into ditches
Eroded banks
Vegetation and silt blocking culverts
Developing sinkholes
Fallen trees damming streams

Be an activist like Chris. Take pictures and report them to the appropriate authorities. That will usually be the City or Flood Control.

You, too, can make a difference.

Posted by Bob Rehak on 11/15/2020

1174 Days since Hurricane Harvey

Save the Date: Kingwood Area Drainage Analysis

Harris County Flood Control District (HCFCD) will hold a Virtual Community-Engagement Meeting for the Kingwood Area Drainage Analysis project: 10/20 at 6:30 PM.

Study Purpose

The purpose: to inform residents about the status of the project and share findings to date.

The Kingwood Area Drainage Analysis focuses on “evaluating the existing drainage level of service for the 32.3-mile open channel network within the greater Kingwood area and identifying the drainage infrastructure which will improve the network’s level of service.”

What That Means

The San Jacinto River Master Drainage Study examined the major streams around Kingwood. But this study examined every stream and ditch within Kingwood. From Taylor Gully, Ben’s Branch and the Diversion Ditch on down to the smallest ones.

When originally constructed, engineers designed ditches to convey a 100-year rain without flooding homes or businesses. However, over time, many have filled in with sediment – often so gradually, the process is invisible. Such ditches may need cleaning out. See below.

*Ditch between Valley Manor and Twin Grove where it goes under Kingwood Drive. Capacity dramatically reduced by sedimentation and vegetation. Photo courtesy of Chris Bloch.*

Also, new upstream development, such as Woodridge Forest and Woodridge Village, may be contributing additional stormwater to ditches during heavy rains. So those ditches may need expansion.

Instead of being able to safely convey a 100-year rain, ditches now might only be able to convey, for example, a 25- or 50-year rain because of such factors.

“Identifying drainage infrastructure which will improve the network’s level of service” means “figuring out what it will take to make them safely convey a 100-year rain again.”

Partially Funded by Lake Houston Redevelopment Authority

The Flood Control District has entered an interlocal agreement with the Lake Houston Redevelopment Authority (TIRZ 10) to partially fund this drainage study. Bonds approved by Harris County voters on August 25, 2018, have funded the rest.

Public Participation Important

Community engagement is an important component of the Bond Program. You live here. You know where the problems are and how high water gets. Your participation is necessary to ensure your safety. Speak up now BEFORE HCFCD begins implementing the program.

If you know of a problem HCFCD is not addressing, you need to tell them.

The virtual Community-Engagement Meeting will be held on:

Tuesday, October 20, 2020
6:30 p.m. to 7:30 p.m.
Join online at PublicInput.com/Kingwood
Or by phone at 855-925-2801 with Meeting Code: 9541

Meeting Format and Other Details

The meeting will begin with a brief presentation to share project updates, followed by a moderated Q&A session with Flood Control District team members.

You can submit questions and comments throughout the presentation. Any comments not addressed during the Q&A session will receive a response after the event.

A recorded version of the meeting will be available on the Flood Control District’s website and YouTube channel after the event.

Meeting accommodations can be made for those with disabilities. If needed, please contact 346-286-4152 at least 48 hours prior to the meeting.

The Kingwood Area Drainage Analysis Technical Report Executive Summary will be available online prior to the October 20, 2020, Community Engagement Meeting at www.hcfcd.org/F14.

For questions, please contact the Flood Control District at 346-286-4000, or fill out the comment form online at www.hcfcd.org/F14.

Posted by Bob Rehak on 10/7/2020

1135 Days after Hurricane Harvey

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