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Flooding

Around 6:30PM Monday evening, West Houston experienced a large, slow moving thunderstorm that dropped approximately 3.5 inches in our area. Lots of street flooding resulted. This was not the event that caused major flooding. That began Tuesday morning, over 8 hours later, between 3:00 and 4:00AM on April 28th, 2009, after these flood waters had long receded. The pictures below were taken at the end of the first event.

Below: I-10 feeder road floods too easily. Below: Briar Branch Creek west of Witte Road. Below: Briar Branch Creek nearly overflows.
Below: The banks are higher looking east towards the Bunker Hill bridge. Below: Briar Branch Creek bridge at Bunker Hill acts like a dam.
Below: Bunker Hill no longer blocks water flowing on Pine Lake. Below: Water can now flow across Bunker Hill to lower properties to the east.

Again, the pictures above were the evening preceding the flooding, but show how a relatively common event of 3+ inches affects the area; however, there are lots of pictures available from the homes of flood victims. Some are included as separate files on this disc.

On page 6 (Section 2.4) of Drainage Study of Briar Branch Creek (38MB), Derek St. John, of LAN, explains that:

“The channel crosses Witte Road through two 48 inch culverts.  The 48 inch culverts also connect to the existing Witte storm sewer (one 8′ by 5’box culvert) that flows south, across Briar Branch.  Water that enters the junction of Briar Branch versus the Witte storm sewer is determined by the current hydraulic head on each system. Water will ultimately follow the path of least resistance.  For the extreme event, storm sewer trunk lines carry very little flow relative to overland sheet flow. W151, the receiving waterway for the Witte Road storm sewer, has been widely documented in other reports as ineffective during the extreme event.”

Why is this important?  Imagine a straw with a hole in its side. Ditch 151 has a hole in it where it crosses Ditch 140, Briar Branch Creek. Water had already been blocked at the end by flooding around the Memorial City area, and water from the flooded neighborhoods Shadow Wood and Pine Villages had filled up Metro National’s Witte Road detention pond, so with both ends of the straw under pressure, water spilled out into Briar Branch Creek, flooding adjacent neighborhoods, then spilled over Witte Road and flowed down Pine Lake. Still more water flooded Gessner.  The Metro National detention pond on Witte spilled into homes of several elderly women, flooding them. Flooding issues North and South of Memorial City are inextricably linked.

Briar Branch Creek was not intended to carry water from both drainage systems, so pipes that normally deliver water to the creek now serve to deliver water into the neighborhood.  And the undersized culvert bridge at Bunker Hill serves as a restriction, backing up water in the Creek faster so that even relatively common events like the 3.5 inch rain on Monday April 27th, causes backflow in the drainage system.

In particular, the dual 2 foot pipes at Windhover are submerged with all but the least amount of rain water. Once submerged, water flows initially floods Windhover at Pine Lake, then further down Windhover and begins flooding Westview and Cedardale.  Water on Cedardale and Pine Lake that was once blocked by the elevated Bunker Hill Road, now freely crosses Bunker Hill and continues to travel down Cedardale to Springrock where it collects in low areas near Westview.

Below: Water backflows into the neighborhood during a rain event of 3″ or more. Below: Notice the water already on Windover. Also notice the low path through the yard that was under water during the next rain event

We know that the Drainage Study of Briar Branch Creek is flawed because it only shows minor street flooding for 100 and 500 year rain events, yet routinely neighborhood streets are submerged.  In the Study, LAN calculated expected flow in Briar Branch Creek by extending existing TSARP calculations that end at Blalock Road with an estimated flow of about 1088 cfs.  The Study assumes TSARP flow numbers at the W140-01-00 bridge at Blalock Road are correct, which are undoubtedly low, then extrapolates them from zero cfs at Gessner to the 1088 cfs at Blalock.  According to our hydrologist, Briar Branch Creek drains approximately 400 acres at Gessner, so the initial assumption is in error.  Furthermore, LAN calculations show that overland sheet flows were substantially greater (3.5X) than the TSARP numbers used so should have been a red flag that the TSARP numbers were too low.

The flawed Briar Branch Creek Study was used to define the culvert sizes for the bridge at Bunker Hill Road. Consequently, the culverts are undersized, acting as a restrictor, causing water to back into the neighborhood via the drainage pipes at Windhover. This water eventually spills across the newly lowered roadway into even lower elevations to the east. Unfortunately, these Study errors rippled into the construction of Bunker Hill Road and its drainage study.

Consider the Bunker Hill Drainage Study where Harris County Flood Control District’s, Myron Harris, made TCB Vice President, Eric Nevil, P.E., add the following statement before they would sign off on the plan. It’s item 4 of page 2:

“Please include in the report of the engineer’s conclusion that the proposed project causes no adverse impact to existing flood conditions up to and including the 100-year event.”

HCFCD evidently had seen the pictures which showed flooding under relatively frequent rain conditions on earlier versions of this DVD that they received, as did PW&E, the Mayor and all City Council Members holding office when I presented it in Council chambers in August 2008. So when the TIRZ 17 Board suggests that the recent rain even was extraordinary and that was why houses flooded, it had to have been greater than any other event in the past 50 years, because this is the first time many of these 50+ year old houses have flooded. Furthermore, hydrologists define a 100-year event for Houston as 13 inches within a 24-hour period. North of I-10, this was not a 100-year event. On page 5 of the Bunker Hill Drainage Study it says:

Hydrologic impact calculations for the 100-year frequency event were completed using the Small Watershed Method (SWM). The SWM was used to develop existing and proposed hydrographs that were then compared, taking into account the increase in impervious cover throughout the project area. The area between the existing and proposed curves(bs) provides the amount of storage required to mitigate for any increase in runoff volume due to the increase in imperviousness associated with the roadway construction. Results of these calculations show that 4.40 acre-feet of storage is required to mitigate the increase in runoff associated with the proposed project. Calculating the storage available in the proposed roadway section (depressed curb and gutter) and the storage available in the proposed storm sewer yields a total of 5.06 acre-feet. Therefore, the need for 4.4 acre-feet of volume is provided by the storage in the proposed roadway and storm sewer

There would seem to be several problems with this approach. First, the increased runoff from a two-year event is usually handled by the roadway itself, but in this case, there is less than an acre-foot of excess capacity for major events. Secondly, as stated above, numerous examples of serious water problems had been brought to the attention of the TIRZ and Public Works and Engineering, including strong suggestions that previous estimates of ponding were gravely in error. And it was ludicrous to expect water to be confined between curbs in a roadway with numerous cutouts for sidestreets that were often at lower elevations. Third, in the TIRZ Contract with the City of Houston under Exhibit A, City of Houston Drainage Improvements, Improvement Projects Description, the TIRZ states that it will Oversize Storm Sewers with Proposed TIRZ Mobility Projects. Lastly, when the PE at TCB consented to sign the HCFCD addendum stating that there be no adverse effects “up to and including the 100-year event”, he negated any this was an Act of God argument because TSARP maps generated for the area from the Briar Branch Creek Study show no adverse effects for most of these homes up to a 500-year event.

Therefore, it is our belief that the flooding that occurred on April 28th was strictly a result of poor engineering.

NOTE: At the November 13, 2014 Spring Branch West Super Neighborhood, Gary Stuzick of Klotz Associates told us that Briar Branch Creek has a Level of Service (LOS) of somewhere between 5 and 7 years, and that they were attempting to raise it to a 10-year LOS by adding large underground Rectangular Box Culverts.  This means that adjacent neighborhoods are protected only up to a 10-year event, not the 100 year event that LAN’s 2007 study had asserted.  The question is whether all the addition development in the area lowered the service level after the LAN study was done, or was the original study in error.

Fidelis Property at 9758 Katy Freeway

The PW&E required drainage study for the Fidelis property states that there is a decrease in runoff water to Briar Branch Creek so they were not required to have additional detention by Harris County Flood Control District (HCFCD). Trammel Crow Residential built apartments on the site of the old Daniel Engineering building that are an even more egregious violation of Chapter 9 requirements.

Presumably the reasoning is based upon analysis of the flow patterns from the original Daniel Industries’ property. This analysis, done by R.G.Miller Engineers, claims that nearly 2.6% previously flowed into the TxDOT’s I-10 drainage system, a little more than flowed into Bunker Hill (6.2%) and the balance (about 91%) flowed into Briar Branch Creek. With their new drainage system, a little more than 59% flows into Briar Branch Creek, none flows into Bunker Hill and approximately 41% flows into the I-10 drainage system. Given that they have allegedly reduced the flow into Briar Branch Creek by 20%, Fidelis was able to justify to Clay Haynes at HCFCD that they do not need detention.

LIDAR elevation maps show that the Daniel property was nearly flat. Notice that Old Katy Road was mislabled as “Katy Freeway Access Road” in the picture. Also note the large drainage ditch along the north side of the old MKT rail line. Much of Daniel’s runoff found it’s way there. And note the amount of permeable space on the property. Many of Daniel’s small labs were pier and beam construction and the flow loops used to prove their designs were above pea gravel. The SE corner of the property that Fidelis bought sold rock. Slabs of rock were vertically aligned or palletized – above permeable ground. After a rain, it was usually a big mud puddle, so it is difficult for nearby residents to understand how public officials can say that “there was equal impervious area”, when clearly there was not.

There are several flaws in this argument.

First, the City of Houston requires detention at a rate of 0.5 acre-feet per acre of increased impervious cover. HCFCD and TxDOT do not and should not figure into this calculation. Nevertheless, despite eyewitness testimony and pictures to the contrary Andrew Ichen, Deputy Director of PW&E; says, “This development creates 0.9 acres of increased impervious cover in the 8.31 acre tract”, in its analysis of pervious versus impervious for both the Fidelis and Trammel Crow properties is less than an acre. Even when supplied with photographic evidence 1, or 2 he restates his position. Michael Marchotte and former Mayor White have both publicly stated that there is equal impervious cover. Why would politicians continue to make fallacious statements when proof to the contrary is so easily obtained? Documents viewed at the Planning Department gave a clue. Indeed, the calculations show that there is only an increase in 0.9 acres. But notice that there’s an unexplained 0.1 acre fudge factor in the calculations. Furthermore, almost a half an acre of the permeable area is supposed to be located inside the courtyards of the apartments. That’s simply * not * true and their own flyer indicates that almost all of the available land in the courtyards is covered by impervious surface. Even the large green square in the apartment’s flyer is actually a large barbecue pit for residents. And the 0.191 acre portion of property at the SE corner of the property is now part of the HEB driveway – nearly totally impervious.

Second, Daniel Industries designed their parking lots to be detention systems.  Concrete was sloped to drains in such a way that water collected in pools and took a while to drain.  As a former employee at Daniel, I remember that the old timers  got a kick out of watching new employees park in areas that traditionally flooded then scrambling out to save their vehicle.  The City of Houston has no way to record information about who  has parking lot detention, but a good hydrologist should be able to recognize it.  Trammel Crow should have replaced the existing detention, then added detention for the additional impervious area that the apartments created.

Third, the Daniel Industries property never fronted I-10. Much of the Daniel water flowed into the giant ditch between the old MKT railroad tracks and Old Katy Road. There were ditches on both sides of Old Katy Road. Was this water accounted for in the Fidelis, TxDOT, or TIRZ drainage studies? We think not.

There was very little water that flowed into the I-10 system because the elevated track bed prevented its flow. Historically, the railroad tracks served as a berm between the I-10 feeder road and the Daniel property and continued to be a barrier to water until Bunker Hill construction was begun, after the drainage study was done. Only then was the hump for the railroad crossing removed from Bunker Hill. Daniel Industries sheet flow was never able to reach the I-10 drainage system.

Then, there’s the issue of raising the entire property an average of 1.5 feet.   MCDDC leased surveying equipment identical to that used by TxDOT to survey I-10.  Referencing the same markers that TxDOT used, we found that the entire property had been raised an average of 1.5 feet, displacing the 69 acre-feet of water.  According to Texas Watershed laws (1), if the property owner changes the flow patterns and causes flooding of neighbors, they can be liable for the damages. Since the Fidelis drainage analysis said that nearly all of the water was captured by Briar Branch Creek and the rest flowed into I-10 or Bunker Hill Road, that implies that previously none flowed into the Old Katy Road and MKT railroad drainage systems. That’s simply not true. Therefore, the flow patterns and the entire Fidelis drainage system is based upon flawed analysis. With a flawed basis as the starting point, the probability is very high that flow patterns were changed. Now every time it rains, the feeder road in front of the Fidelis property floods, and it’s not just the outer lanes. A 2 to 3 inch downpour floods all the lanes.

Furthermore, in an extreme event the steep driveways of the Fidelis property funnel water into Bunker Hill where it joins water from the flooded feeder road. Now no longer blocked by the MKT railroad tracks, excess feeder road water flows down Bunker Hill and east down Long Branch, Pine Lake, Larston, and Cedardale. Many neighbors described the “river of water” traveling down their streets to lower areas during the April storms.

Although Daniel installed a drainage system on their engineering building on Pine Lake Drive, the properties on Old Katy Road primarily relied on natural drainage patterns; that is, the prevailing northwest to southeast slope of the land. It is very difficult to believe that 91% of the water on the old Daniel property arbitrarily decided to make its way against the natural slope and into Briar Branch Creek. Again, LIDAR elevation maps clearly show the prevailing slope of the land.

TxDOT representatives at the Village’s Flood Meeting on August 20, 2009, stated that TxDOT will handle the first 150 feet of frontage along the I-10 feeder road. The Fidelis property extends about 1800 feet along the feeder road from from Bunker Hill going west. This corresponds to an area of about 6 acres, yet the drainage analysis, done by R.G.Miller Engineers, says that 16 acres is drained into the I-10 drainage system. So TxDOT is draining 2 2/3 times more than they should be and TxDOT expanded the I-10 drainage area feeding the W151 drainage system by over 70%. Perhaps these are the reasons why the feeder roads flood whenever it rains.

As for the Grandfathering argument that has frequently been used by Public Works & Engineering (PW&E) officials, Fidelis put together various land parcels (at least 4) and divided others. All these transactions would have required some replatting and, hence, reset the requirements for detention to current standards. Besides, Daniel Industries was established in 1955, before the city had rules about detention and before the Interstate system even existed. Anyway, the City line didn’t extend that far. Our local government and PW&E should be ashamed if this sort of Grandfathering is routinely used as a a valid reason not to install adequate detention.

 

Residents Against Flooding (MCDDC) our Drainage Coalition

Who we are – The April 28, 2009, flooding in the Memorial City area amplified the flooding concerns and problems of residents in the area roughly bounded by Memorial Drive on the south side, Beltway 8 on the west, the drainage basins of W140-01 and W151 on the north side and Hedwig Village and Bunker Hill Village on the east.  Residents within this area formed MCDDC.

This area has had an escalating history of significant flooding problems despite numerous drainage projects. While a project’s design scope might bring relieve to a particular area, it often does so without regard for downstream or adjacent affects. Further changes to the drainage systems caused by commercial development and redevelopment, and a number of drainage projects in various stages of planning, design and construction by Memorial City TIRZ 17, will have uncertain impacts on nearby residential neighborhoods. I-10 reconstruction significantly increased the amount of impervious area and included a new drainage system that has almost certainly impacted water flow in the area. Early indications are that area flooding has been made worse. Construction of the recently redesigned W153 system (the ‘Fonn Villas’ project) had very significant flooding impacts to nearby homes. The updated W151 study, recently completed by HCFCD, developed several alternative plans for improving drainage in portions of the MCDDC area. However, preliminary reviews of the W151 system indicate that it fails to account for changes in the I-10 drainage area and new drainage systems that have been severed from the W151 system. Our members are concerned that these disparate systems do not seem to function well together and are looking for independent guidance.

Ed Browne 9/11/09

Editor’s note 7/18/11 – this document was originally written and passed out on a DVD  to each sitting Houston City Council member and the Mayor’s office fully a year before the flooding.  After the storm, the section above entitled April Flooding and Its Causes was added and the DVD was again presented to City Council.   When no action was taken, MCDDC was formed and money was raised to hire environmental attorney, Jim Blackburn, who hired independent hydrologist, Larry Dunbar, to find out what happened.  Since then Larry Dunbar’s Report was finished, Harris County Flood Control completed a study of W151, MCDDC’s membership voted to proceed with a lawsuit against TIRZ 17, and TIRZ 17 commissioned and  LAN completed the TIRZ 17 Regional Drainage Study.  As a result of all these actions, a new detention pond is planned for an area east of the Bunker Hill bridge adjacent to the existing Costco detention pond.  While we welcome a new detention pond, in these economic times wise spending is paramount.  It is our fear the the undersized bridge will restrict water from getting to the detention pond, rendering it less effective.