On September 27, 2018 Version 2.0 of the National Oceanic and Atmospheric Administration’s Atlas 14, Volume 11 was released and a press conference was held. As I’ve described in previous posts, Volume 11 provides us with a more accurate picture of the annual probability of rainfall of various depths and durations across the state of Texas.  These data were last updated across the entire state in 1961.  Volume 11 was created by evaluating rainfall records as early as the 1870’s up through 2017.

As I written previously, the depth of 1% annual chance, 24-hour rainfall is a key design storm we use for drainage and flood risk reduction infrastructure in the Harris County area.  Prior to Volume 11, this key design storm was about 12.4-inches in western Harris County and about 13.5-inches in southeastern Harris County, as shown below.

After Volume 11’s release the new 1% annual chance, 24-hour duration rainfall map for Harris County looks like this:

We used to believe that the 1% annual chance, 24-hour storm was 2.6-inches to 4.5-inches smaller than it actually is. This was because the rainfall records did not span as long a period as they do now. Our uncertainty bands have gotten a bit narrower and the overall magnitude of most storm frequencies and durations have increased.  The actual depth of the 100-year, 24-hour duration rainfall ranges from 21% to 33% higher than we thought.

The updated information is presented by NOAA using a web-based map interface, located here: https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html. It allows anyone to double click on the map at any point of interest and instantly get both a tabular and graphical display of the rainfall stats.

Here’s how it works for my neighborhood in west Houston.

This first image is from the map interface. I have zoomed into my part of town and have double-clicked on the map near my house. The red cross-hairs show the click point.

After double-clicking the following information appears below the map:

This shows that my house has a 1% annual chance of receiving 16.5 inches (or more) of rain in 24-hours.  If you read the fine print you will see that there is a 90% chance that the actual rainfall depth for this 1% annual chance, 24-hour storm ranges will be somewhere between 11.6 inches and 23.5 inches, because of the uncertainty of our statistical estimate.  The website also provides a graphic version of the same data:

The website also provides a graph that illustrates the confidence bands around the estimated rainfall depth. The figure below shows confidence range for all 24-hour storms.  The green line shows the upper limit of the 24-hour rainfall depth and the red line shows the lower limit. There is 90% chance that the “true” rainfall depth will fall in between those values (for any given recurrence interval).  Please recall that “recurrence interval” is the inverse of annual probability.  So the 1,000-year storm has a 1/1,000% chance of occurring in any given year.  If you convert the fraction to a decimal, that’s a 0.001% annual chance. Notice how that is not zero?

See how the confidence range grows for the larger, more rare events?  The 100-year recurrence interval corresponds to the 1% annual chance event. The math tells us that there is 90% chance that the 1% annual chance, 24-hour event is somewhere between 11.6 inches and 23.5 inches. The corollary is there is 10% chance that the real depth is outside that range.

The expanding confidence interval – the gap between the green line and red line – makes sense because we have statistically evaluated rainfall records that only go back to, at best the 1870s, and, at worst 1970’s.  This is a period of record of only between 47 and 148 years.  So our certainty about 500-year or 1,000-year recurrence interval events is low.

In my next post I will be providing some thoughts about the cost impacts of this refined view of our rainfall statistics.

On September 2, 2018, the Houston Chronicle published “Remember the Villains of Hurricane Harvey” as their lead editorial. The byline was listed simply as “The Editorial Board.”  The editorial board is currently composed of the following people (just in case you wondered):

• John McKeon, Publisher.
• Jack Sweeney, Chairman.
• Lisa Falkenberg, Opinion Editor.
• Evan Mintz, Deputy Opinion Editor.
• Jim Newkirk, Outlook Editor.
• Andrea Georgsson, Sunday Outlook Editor.
• Harold Jackson, Editorial Writer.
• Andrea White, Editorial Writer.

STAR WARS meme prepared by m. bloom paraphrasing the lead editorial only slightly.

The editorial called for Houstonians to remember villainous developers “who saw nothing wrong with building neighborhoods inside the flood pools behind Addicks and Barker reservoirs, and then kept the risks to themselves.”

First, some definitions of the word “villain,” to place the editorial in the proper context:

Dictionary.com: Villain: (1) a cruelly malicious person who is involved in or devoted to wickedness or crime; scoundrel; (2) a character in a play, novel, or the like, who constitutes an important evil agency in the plot.

Merriam-Webster: Villain: (1) a character in a story or play who opposes the hero; (2) a deliberate scoundrel or criminal; (3) one blamed for a particular evil or difficulty. 

Cambridge: Villain (1) a bad person who harms other people or breaks the law; (2) a cruel or evil character in a book, play, or film.

Let’s break this down one bit at a time.

The developers (and the professional engineers who designed their developments) invested private capital to provide affordable housing on privately-owned land, with an annual risk of flooding of much less than 1%, which is the consensus standard used by all communities in the United States to design and locate new homes and other structures.  Engineers designed streets, lights, traffic controls, water systems, wastewater systems, and drainage facilities that functioned perfectly from the day they were built until Harvey arrived.

I believe that the engineers designing these neighborhoods did so in compliance with Sections 137.51 through 137.55 of the rules promulgated by the Texas Board of Professional Engineers under the legal authority of the Texas Engineering Practice Act.  These rules require engineers “to safeguard, life, health and property, to promote the public welfare” as well as “to protect the health, safety, property, and welfare of the public.” Please note that this rule does not require engineers to design neighborhoods with zero risk of flooding.

Why do I believe that the developers and engineers acted ethically and appropriately? Simply because the health, safety, property, and welfare of the residents were safeguarded.

Because the potable water provided to the residents was clean and healthy every day until Harvey arrived. Ever try to raise a family without potable water?

Because sanitary wastewater was collected from every home, treated, and properly discharged into nearby bayous every day until Harvey arrived.  Ever try to live in a home without a toilet or proper wastewater facilities?

Because none of the homes fell down on their owners every day until Harvey arrived and even during Harvey.

Because the roads carried traffic every day until Harvey arrived. What if there were no roads? Because the traffic lights and street lights worked every day until Harvey arrived. What if there were no lights?

Because rainwater from storm after storm was carried downstream from the developments without flooding anyone every day until Harvey arrived.  Because the systems worked.

All of these critical public health, safety, and welfare facilities were designed by ethical engineers with private funding from developers. All of the facilities and homes were made possible by the developers who invested private capital to create desirable places for people to live with a low and acceptable level of risk.

We’ve already decided to push our inundation risk exposure down for new construction in the City of Houston and Harris County to significantly less than 0.2% per year. Note that a finished floor elevation placed 2 feet higher than the 500-year flood elevation has an annual chance of inundation of much less than 0.2% per year in most places in this region.

But, if we collectively wish to retrofit existing homes and businesses in our region that are exposed to higher annual risk levels than 0.2% or 1% (think Hunting, White Oak, Brays – but certainly not neighborhoods in the Addicks or Barker flood pools) we need to have an open conversation about the desired risk level, the costs to achieve it, and the benefits realized.

We should avoid villainizing folks that built communities and facilities that worked and that beat the desired risk levels established at the time those facilities were built.

The villains pictured below are not developers.

A still from the silent comedy, Barney Oldfield’s Race for a Life MACK SENNETT/PUBLIC DOMAIN

On August 24, 2018, the Texas General Land Office released a new report entitled “Hurrican Harvey: Texas at Risk” the presents lessons learned, recommends policy changes, and administrative actions, mostly around housing.  This post will highlight the key recommendations included in the report.

The following recommendations are directly from the report’s Executive Summary (bold text added by me).

1. The State of Texas should create a Business Advisory Council on Disaster Recovery and Mitigation to access private business expertise and as a conduit for problems they have in disaster recovery. The Council would not have the authority to spend money or write regulations but would provide much-needed private sector advice and expertise.
2. The Texas Water Development Board’s statutory authority should be substantially expanded to cover flood control and have directive control over the state River Authorities in carrying out these duties. The same Board should have directive control over drainage districts to ensure they are keeping drainage ditches and waterways in a continuous state of repair.
3. The State of Texas should establish a permanent disaster recovery training center for local government officials focused on recovery, disaster fortification, and resilience.
4. The state legislature should establish by state statute a Regional Building Code District (RBCD) with standard-setting authority in the high-risk hurricane region of Southeast Texas which would replace the existing weak and uneven building code system. The Commission would have oversight over building codes in the RBCD which will be composed of the following ten Councils of Government or regional planning areas: Lower Rio Grande Valley, Coastal Bend, Golden Crescent Regional Planning Commission, Houston-Galveston Area, Central Texas, Alamo Area, Brazos Valley, Capital Area, Deep East Texas, and South East Texas. These are the areas historically most at risk of hurricane flooding and wind damage.
5. The state should fund at least 75% of the salary costs of building code enforcement (local inspectors and third-party contractors working for cities and counties) with 25% funded by building permit fees in this new Regional Building Code District. The same capacity strengthening salary program should be extended by the State of Texas for city and county recovery managers.
6. This report recommends that a large reserve account be established using federal funding initially before the next hurricane season later funded by state, city, and county resources to accelerate the existing housing buyback programs for homes which repeatedly flood. Counties and cities participating in these programs would then take the homes out of use and the property used for green space. This fund would be used in the weeks following a hurricane or flooding event before private companies purchase the properties that have a repeated history of flooding. The state legislature should also require rental units or houses for purchase which have repeatedly flooded to disclose this in rental or purchase documents and title registrations.
7. This report endorses the efforts of city and regional planning groups in Texas buying land at market prices without the use of eminent domain to reduce the risk of flooding and preserve reservoir water recharge. This report recommends the state legislature create a commission to study this land purchase program and report on what might be done by the state to support these efforts in the future.
8. Texas should continue to support private philanthropic programs after major disaster and develop a system to integrate public and private sector efforts to help survivors of natural disasters without endangering the independence of the private social service groups.
9. The GLO should implement a saturation Public Information Campaign before and during every hurricane season to ensure the local officials and the public understands what FEMA’s temporary housing programs will provide and what it will not provide under existing federal law in the event of a major hurricane or flooding event.
10. The federal government should consolidate funding for all temporary FEMA housing programs into one block grant to states with a high risk of natural disasters.
11. The GLO should bid out indefinite quantity contracts (IQCs) for information management, construction, and other engineering construction services under the Federal Acquisition Regulation (FAR) procedures before the annual hurricane season each year, so contracts are in place to be used within a week of a major disaster.
12. Congress should grant “notwithstanding authority” to those high disaster risk states which have demonstrated competency in disaster response and recovery for one year following a major disaster. This would allow the waiver of most federal procedural regulations and speed contracting and program management.
13. Congress should expand the definition of what is eligible for reconstruction using FEMA temporary housing funds under the Stafford Act so that damaged housing can be rebuilt to be more resilient and fortified to withstand disasters in the future. In the absence of the phase-out of recreational vehicles and mobile housing units by FEMA, the state legislature should give the Governor the authority to waive city and county prohibitions of their use for one year after a Presidential disaster declaration.
14. Should the federal government expand the definition of what is permissible for reconstruction funding within FEMA programs, the GLO should investigate and consider using new technologies for housing construction which are less expensive, more resilient, and can be implemented faster than traditional housing construction techniques.
15. Congress should enact legislation to consolidate disaster housing programs of FEMA, HUD, and the SBA into one agency or department to eliminate competing missions and business systems which slow down the temporary housing response.
16. Congress should amend the privacy act to give state and local officials managing disaster response and recovery efforts full access to survivor information generated by FEMA if they have applied for and are qualified for assistance. An integrated database should be built from the beginning with full access by state and local recovery and housing response administrators. In the absence of such a change in law, we urge FEMA to amend their benefits application form to allow
    people to voluntarily make their data available to state and local government agencies in order to provide them services.
17. HUD should rewrite the formula for the allocation of funding to municipal and county governments directing aid to low and moderate-income people so that all people in these categories are assisted.
18. This report endorses acceleration of the studies needed to advance the Texas Coastal Barrier System and Upper Texas Coastal Levee system, and the funding of these projects by the U.S. government.

I’ll post a little narrative summary of the findings at some point, but here is the slide deck I presented on August 13, 2018, in Nashville at the International Low Impact Development Conference, hosted by the Environmental & Water Resources Institute of the American Society of Civil Engineers.

Birnamwood Drive Results Presentation (2018)

I was saddened to see the videos and read the news stories about the flooding and landslides which occurred in Japan over the past several days.

Photo: Baltimore Sun

As of this writing, more than 179 people have been confirmed killed and 8 million people have been ordered to evacuate their homes.

Photo: Toronto Star

The flooding in Japan illustrates that Houston is not alone in dealing with flood risk. The news prompted me to do some research into the situation in Japan. This post provides some additional information about flood risk management and hydrology in Japan.

The first important difference between Japan and Houston is topography.  The rivers in Japan are very steep and convey water with high velocities.  The graphic below, which I adapted from a figure in an un-dated publication of the Network of Asian River Basin Organizations (NARBO) called “Flood Management in Japan,” illustrates the river profiles (horizontal distance and vertical fall) for selected rivers in Japan (blue) and some selected rivers in other countries (green).

When Dutch engineer Johannis de Rijke saw the Jōganji River in Toyama Prefecture (the steepest one shown above – to the far left) he famously said: “this is not a river [its] a waterfall.”

The topography in Houston is very, very flat. I added the approximate profile of Buffalo Bayou from the Barker Dam to Upper Galveston Bay in pink.

Flood risk literature generally reports that about 5% to 14% of the population of the United States lives in a mapped flood risk zone (1% annual chance).  In Japan, due to the steep, mountainous terrain, the populated areas are located in the flatter, alluvial plains between mountains and towards the mouths of most rivers.  The publication referenced above indicates that 50% of the Japanese population are located in these alluvial plains. I was not able to locate flood risk mapping products indicating what annual chance risk exposure they have.

I was able to locate information about rainfall statistics. A paper from 2017 by Sugi, et. al. used a statistical method called “extended regional frequency analysis” (ERFA) to evaluate three sets of rainfall data to estimate the depth of the 1% annual chance, 24-hour storm. This method is similar to the Atlas 14 project approach I’ve posted about on September 27, 2017, November 20, 2017, November 24, 2017, December 7, 2017, and February 21, 2018.  The three sets of rainfall data they evaluated were:

• Actual rainfall observations from 1979 to 2006, across a wide (regional) geographical area;
• Modeled rainfall observations using ocean temperatures, atmospheric carbon dioxide concentrations, and atmospheric aerosol concentrations from 1979 to 2003, across the same wide geographical area; and,
• Modeled rainfall observations using ocean temperatures, atmospheric carbon dioxide concentrations, and atmospheric aerosol concentrations predicted from the IPCC RCP8.5 scenario for 2075 to 2099, across the same wide geographical area. The RCP8.5 is a “worst case” simulation of unrestricted carbon emissions.

The results of these evaluations are presented below in a graphic that I adapted from the paper.

The key takeaways:

• Some of the inland, higher elevation areas of Japan have a less than 1% annual chance of getting 10 or more inches of rain in 24-hours.
• Some coastal areas in the south have a 1% annual chance of seeing 24 inches or more of rain in 24-hours. Compare that to Houston’s current 1% annual chance, 24-hour rain depth of about 13.5 inches.
• Climate change is projected to expand the areas with a 1% annual chance of seeing 24 inches of rain, or more in 24-hours.

Now let’s compare these data to what happened in Japan on July 6, 2018. Much like our own Harris County Flood Control District “Flood Warning System” gauge network (with 163 gauges), the Japan Meteorological Agency (JMA) operates a network of 160 rain gauges and 20 Doppler radar stations across Japan. On July 6, 2018, the JMA recorded rainfall depths up to 15 inches in 24-hours in specific locations and over 7 or 8 inches of rain over widespread areas of southern Japan. The graphic below was adapted from JMA historical data maps obtained from their data web page.

The gauge locations with the black diagonal line and box indicate new 24-hour rainfall depth total records for that gauge location.

So the high rainfall totals coupled with the steep terrain and people and infrastructure located in the alluvial plains all combined to lead to the loss of life and infrastructure damage.

There quite a buzz these days about significant private investment flowing into cities to build green stormwater infrastructure. It is a noteworthy trend, and after Harvey, more than one group has asked me about how they might help make that happen in Houston.

The question is why is this happening in other places and not so much in Houston?  What makes a private equity firm or an institutional investor jump at the chance to finance some green public infrastructure projects?

To be clear, this is different than private philanthropists making grants to Houston area projects, like the Bayou Greenway, the Museum of Fine Arts, Discovery Green, or Memorial Park. Those are pure gifts where the grantor does not expect to be paid back.

This post is about private investors lending money for green stormwater projects, getting paid back, and earning a reasonable amount of interest on their money.

PHOTO CREDIT: Organisation for Economic Co-operation and Development

Some recent examples are illustrative:

1. District of Columbia Water and Sewer Authority (DC Water) Environmental Impact Bond: In 2016, Goldman Sachs and the Calvert Foundation announced that they would purchase the first environmental impact bond (EIB) issued in America to fund the construction of $25 million of green stormwater infrastructure (GSI) in the Rock Creek sewershed. DC Water agreed to build GSI in public rights of way, with investor oversight through their independent technical agents. The GSI performance risk will be shared by DC Water and the investors. Everything depends upon the volume of stormwater runoff reduction achieved. If runoff volume reductions are higher than forecast, DC Water will pay a 13.2% premium to investors. If runoff volume reductions are lower than forecast investors will pay a 13.2% risk-sharing payment to DC Water, and if runoff volumes are in expected ranges than no contingency payment will be made and the bond will be paid back at the nominal 3.43% discount rate.
2. Maryland’s Prince George’s County “First of its Kind” Public-Private-Partnership:  In March 2015, Corvias and the county signed a $100 million, 30-year partnership contract with great fanfare. Their “Clean Water Partnership” was created to assist the county to achieve federally mandated reductions in pollutant discharges in urban stormwater runoff to the Chesapeake Bay. The county will use its own traditional design-bid-build approach to deliver green stormwater retrofits on 2,000 acres of publicly owned land while Corvias will be responsible for delivering an additional 2,000 acres. This will allow a direct comparison of the speed, effectiveness, and overall costs of using both delivery methods.  The combined effort will achieve 50% of the federally mandated retrofit requirement of 8,000 acres, with the balance of the work to be completed later using the winning process. These details are from the program FAQ.
3. City of Baltimore and the Chesapeake Bay Foundation “Pay for Success” Model: In March 2018, the City of Baltimore, Quantified Ventures, and CBF announced that they will work together to create innovative Environmental Impact Bonds (EIB) to help pay for more than 90 green stormwater retrofit projects in the city. Baltimore will issue up to $6.2 million worth of EIB financing. The proceeds will be used to implement the retrofit projects and the repayment of the bonds would be based on the effectiveness of the projects.  The city is under a federal mandate to reduce the volume and pollutant loads of water flowing to the Chesapeake Bay.

All of these examples of private investment in green stormwater systems are successful because the private investors have a high degree of confidence that the revenue stream will continue and that they will be paid back, with interest.  The investors have a high confidence level because in all of these examples the green stormwater projects MUST be built because of regulatory mandate that is memorialized in a consent decree issued by a federal court.  This provides a much higher level of funding certainty than the normal annual political budgeting process that most municipal governments undertake.

The future revenue stream in the DC Water example is driven by a court-ordered mandate to mitigate combined sewer overflows. DC Water MUST reduce runoff volumes. Prince George’s County is subject to a settlement agreement stemming from a federal lawsuit over the Chesapeake Bay restoration, therefore, that revenue stream is all but certain. Baltimore also is subject to the terms and conditions of a federal combined sewer overflow mitigation consent order.

Does this revenue certainty exist in Houston?

In a word: no.

The ballot language for the city’s celebrated “lock-box” for streets and drainage that was producing about $400 million each year – known as “Rebuild Houston” – was defeated in court and now must be reaffirmed by voters in November 2018. The result of that election is not certain. Even if that election was a “sure thing,” the appropriation of funding to any particular green stormwater project, or set of projects, is still subject to the political process and, frankly, bureaucratic resistance to change.

The city is not subject to any type of stormwater quality mandate, other than to comply with its stormwater quality permit, which imposes only narrative provisions that don’t drive the construction of public green infrastructure projects.

The city also (thankfully) does not have a combined sewer system and, therefore, the city does not have any mandated need to invest in combined sewer overflow mitigation projects using green stormwater infrastructure.

So the challenge for Houston is this: Can we create a business model that produces a reasonable return on investment for green stormwater infrastructure project financing?

On June 21, 2018, Zurich Insurance Group released a new report called “Houston and Hurricane Harvey: A Call to Action.”  Prepared by The Institute for Social and Environmental Transition–International (ISET-International), the American Red Cross Global Disaster Preparedness Center, and the Zurich Insurance Group, the report includes a five-page executive summary along with sections summarizing hurricane event statistics, why Houston is so flood-prone, various methods of risk reduction, information about the region’s initial response and recovery, priorities and gaps in long-term recovery and resilience, lessons learned, and specific recommendations.

The report includes recommendations that relate to the social and cultural aspects of resilience that I thought were noteworthy. Regular readers know I normally discuss engineering or regulatory issues.

Buy Flood Insurance

The report calls for efforts to “make flood insurance more universally appealing for homeowners and businesses.” The report suggests that our communities should undertake “awareness campaigns” to increase the demand for flood insurance – even in lower risk areas, outside of the regulatory floodplain, where insurance is relatively inexpensive – to enable policyholders to recover more quickly and to thus be more resilient.  [A higher number of lower risk policyholders would also help with the ongoing fiscal defects in the National Flood Insurance Program.]

The term “appealing” is an interesting word choice – I’m not sure we could ever make buying insurance appealing, but maybe? There are probably some smart social scientists and public relations firms that could use the power “social norms” to increase the number of flood insurance policies purchased in this region, but that effort would need to be nearly continuous to influence all of the new people moving here each month.

I snapped a photo of this poster in the tunnel just outside 611 Walker, home of Houston Public Works, in July of 2017, before Hurricane Harvey:

This is at least one example of local communities making some effort to encourage citizens to purchase insurance. The report indicates that Harris County Flood Control District is planning to promote insurance coverage with a billboard campaign (p. 38).

Culture of Awareness

The report also calls for us to “build a culture of awareness around risk” and to “incentivize incremental small decisions by residents and businesses that collectively reduce exposure and risk…to reduce the surprise element of flooding.”  The report suggests installing public markers indicating previous flood inundation levels and road signs indicating that “You Have Entered a Flood Control Reservoir,” and similar measures (p. 40).  I’m not sure that this type of information disclosure would be embraced by the larger community.  According to Jim Blackburn, inundation level signs were installed in at least one Galveston Bay area neighborhood that is subject to storm surge; but the signs were removed after about 30 days due to complaints from realtors (see time-stamp 26-minutes, 50-seconds in this video).

The report suggest that the Houston region, like Galveston, “wear its [flood] battle scars with pride.” The authors suggest that homes that flooded should be encouraged to “mount a plaque … proclaiming: ‘This home survived Harvey; the water was x feet deep.’ ”

Business Continuity Plans

The report acknowledges that “even the best … grey infrastructure [and] green solutions … will never reduce flood risk to zero” and it goes on to encourage the development of business continuity plans and household level preparedness plans to help further reduce risks. The report includes a good overview of the key elements of a business continuity plan – which is intended to increase the likelihood that a business might stay in operation throughout a disaster or at least, get back to full operation more quickly. The main elements are:

1. Identify Key Assets: For a consulting firm, it might be ensuring that employees have continued remote access to all files and intellectual property. For a coffee shop, this might mean protecting the espresso machine.
2. Consider Preparedness as Business as Usual:  Incorporate a “disaster day” into the regular schedule of work. Run drills or practice days on a routine basis.
3. Implement Infrastructure Solutions: Install floodgates. Store documents and materials at a protected location. Relocate items after receiving notification.
4. Use Existing Assets: Use security systems to track and evaluate conditions in inaccessible work locations.
5. Assist with Employee Preparedness: Household preparedness plans help business employees return to work more quickly.  A robust communication system is needed to allow the business employer and employees to communicate updates to each other. Employers can prompt employee action with a series of awareness questions related to supplies, backup power, and backup lodging plans.
6. Purchase Insurance: Businesses should obtain insurance. They should consider the full range of options available after speaking with experts. Costs should be evaluated against the full cost of both damages and lost revenue during an extended closure.
7. Support Employees and Community with Recovery: Businesses should support both employees and the larger community with recovery. This might include providing equipment, foods, access to showers or facilities, assistance with clean out / muck out work, and offering paid time off for employee victims.

Recovery Priorities

The report provides an almost accurate picture of our current priorities. It correctly notes that Houston and Harris County both strengthened their floodplain regulations. It indicates that buyouts are underway, but are taking too long and are underfunded. It notes that we are having lots of discussion about a third reservoir to address the Cypress Creek overflow, but it does not fully acknowledge how that project was proposed to mitigate future development and not necessarily to reduce flood risks for downstream properties. The report points out the general lack of state funding for recovery, especially from the state’s “rainy day fund.” ($150 million has been provided for debris removal and to avoid a property tax hike.) The report accurately indicates how recovery support has been distributed inequitably. The report suggests that we are not talking about general drainage infrastructure improvements and maintenance.  I think this was likely just due to the timing of the report; they must have gone to press before the authors heard the announcement of the $2.5 billion Harris County Flood Control District Bond Election scheduled for August 25th and the placement of a reauthorization of the Rebuild Houston program back on the ballot this November.

Overall, the report is a good addition to the growing list of post-Harvey literature and studies. Worth a read.

The Urban Resilience Program of the Urban Land Institute (ULI) just published “Ten Principles for Building Resilience,” with funding from The Kresge Foundation and The New York Community Trust.

The report emerged from a workshop of ULI members who had previously participated in volunteer, pro-bono, group consulting assignments (called advisory panels) to help various communities with resiliency questions or challenges. Workshop participants included a multi-disciplinary group from around the country.

The publication provides the following ten principles:

1. Understand Vulnerabilities
2. Strengthen Job and Housing Opportunities
3. Promote Equity
4. Leverage (Existing) Community Assets
5. Redefine How and Where to Build
6. Build the Business Case (for Resilience)
7. Accurately Price the Cost of Inaction
8. Design with Natural Systems
9. Maximize Co-Benefits
10. Harness Innovation and Technology

It also includes a good definition of resilience, which states that resilience is:

the ability to prepare and plan for, absorb, recover
from, and more successfully adapt to adverse events.

When I read this definition my big take away was this: this definition acknowledges that some future adverse event WILL happen.  This definition does not shy away from the reality that we can’t reduce the risk of a future adverse event occurring to zero.

The graph below illustrates this point.  The horizontal axis is the amount of time you are willing to wait to see if a rare event will occur.  The vertical axis is the probability of that rare event occurring over during that time duration.  Each colored line indicates the annual chance of the adverse event occurring.

This graph illustrates that if the finished floor of the living room of your house is 1-inch below the 100-year floodplain water elevation (which has a 1% annual chance of happening – the red line) you have a 26% chance of having 1-inch of water in your home during a 30-year mortgage period.  If you read the horizontal axis of the graph over to the 30-year duration mark (the second line to the right of the 10-year mark on this log scale), you will see it intersects the red line at exactly 26% on the left axis.

I support resiliency planning and thinking about our response to Harvey and other adverse events as a risk reduction effort and as a process to reduce the negative outcomes. This approach is much better than the old-school thinking that suggests that we can use engineered infrastructure to “control” nature, flooding, or other adverse events from occurring in the first place.

We can use planning, engineering, and architecture to reduce risks, to prepare for adverse events, to stage recovery efforts ahead of time, and to adapt to the eventual (certain) arrival of the next adverse event.

We can use insurance, reinsurance, and catastrophe bonds to hedge against residual risks that are not possible to eliminate.

I think I like where this is going…

How many times in the last nine months since Hurricane Harvey have you heard someone mention something about building a “third reservoir?”

If I had a dollar for every time I heard or read about that, I’d have enough money to pay for it. (Well not actually, but you get the joke.)

This post provides some information on all three of the “third” reservoirs that I’ve heard about. Please add some information about any additional “third” reservoirs you’ve heard about in the comment section below.

White Oak Reservoir (1940)

The earliest mention of a third reservoir I can find is from the U.S. Army Corps of Engineers “Definite Plan” of 1940.

This reservoir was known as the “White Oak Reservoir” and was proposed to be located just north of the area of the future intersection of US 290 and IH-610, near the future T.C. Jester and future West 34th. (Well before those roads were built.)  Here’s a map of the general location with our modern road network and current floodplains shown.

Here’s an image of the reservoir from the original, hand-drawn plans prepared by the U.S. Army Corps of Engineers in 1940.

Key statistics about the proposed 1940 White Oak Reservoir are provided below:

• Drainage Area:                                            72 square miles
• Site Area:                                                     4,280 acres
• Maximum Berm Height:                               35 feet
• Storage Volume:                                          24,400 acre-feet
• Peak Water Surface Elevation:                    84 feet above mean sea level
• Discharge Rate:                                           23,500 cubic feet per second

The White Oak Reservoir was designed to reduce the risk of flooding of downstream areas by capturing, holding, and rerouting larger storms up to a specified large, but rare, depth and intensity of rainfall.

If built, the White Oak Reservoir would have captured stormwater runoff generated from a specific amount of rainfall falling on 72 square miles of the upper portion of the White Oak Bayou watershed.  It would have slowly released the captured water through two planned conveyances. One conveyance was the proposed North Canal, which was a 20-mile long ditch about 30 feet deep that could carry 22,000 cubic feet per second of water. The second conveyance was about 2 miles of channelized Brickhouse Gully that was to carry about 1,500 cubic feet per second into Buffalo Bayou (with obstructions removed).  See detailed image from the 1940 plan set below:

The Cypress Creek Overflow

In order to more fully understand the purpose of the other two proposed “third reservoirs,” it is important to know about the Cypress Creek Overflow. As described in the Final Study Report: Cypress Creek Overflow Managment Plan (August 18, 2015), prepared for the Harris County Flood Control District, Harris County, and the Texas Water Development Board by Michael Baker International (Burton Johnson, P.E.), SWA Group, and Mitigation Resources; the Cypress Creek Overflow,

refers to a large overflow of stormwater runoff from the Cypress Creek watershed into the Addicks and Barker Reservoir watersheds during moderate to severe storm events in the upper Cypress Creek watershed, upstream of US 290. When rainfall levels … [exceed 5.8 inches in 24 hours] ... runoff drains into upper Cypress Creek and makes its way downstream. The overflow begins to occur at the point where the creek shifts from a north-south flow direction to an east-west flow direction near the Waller-Harris county line, and has the potential to inundate substantial areas of land as the overflow makes its way overland south toward tributaries of Addicks and Barker reservoirs and finally to the reservoirs themselves.

Here’s an image from the report illustrating the area of overflow inundation that occurs from a 5.8 inch, 24-hour rain event (which has a 20% annual chance of occurring):

The area above the purple line normally drains north towards Cypress Creek. This illustrates the water overtopping the purple line (the watershed divide — a line of relatively higher ground which parallels the creek) and flowing into the Addicks Reservoir watershed.

In 2014 the overflow was estimated to inundate about 20,000 acres of undeveloped, privately owned land in the Addicks Reservoir watershed during the 1% annual chance rain event (13.5 inches in 24-hours). Development trends and the demand for housing suggests that this area will become developed over time. The management plan study evaluated various options to mitigate the increase in stormwater runoff volume anticipated with that development.

An increase in stormwater volume is expected, even with existing detention and drainage design rules, because our current stormwater mitigation approach only addresses the change in peak flow rate; not the overall volume of runoff. [If desired you can read more about this here.]

Two of the main options evaluated to mitigate the increase in stormwater volume included storage facilities, the reservoirs discussed below.

Mound Creek Reservoir (2015)

The Mound Creek Reservoir was proposed to be located just downstream of the confluence of Mound Creek and Live Oak Creek in Waller County and partially in Harris County. See map below.

Key statistics about the proposed Mound Creek Reservoir are provided below:

• Drainage Area:                                            36 square miles
• Site Area:                                                     3,765 acres
• Maximum Berm Height:                               22 feet
• Storage Volume:                                          15,730 acre-feet
• Peak Water Surface Elevation:                    188 feet above mean sea level
• Discharge Rate:                                           2,000 cubic feet per second
• Benefit to Cost Ratio:                                   1.14

The proposed Mound Creek Reservoir was devised to capture some of the stormwater that overflows the Cypress Creek channel and floodplain and would otherwise flow into the Addicks Reservoir.  After capture and detention, the Mound Creek Reservoir would release the water to both to Mound Creek and to Live Oak Creek at controlled rates.

Approximately 1,580 acres of land below the Mound Creek Reservoir would be preserved as a conservation area suitable for periodic inundation.  This will help store additional waters in a more shallow environment and help manage the overflow zone.

Katy-Hockley North Cypress Reservoir (2015)

The Katy-Hockley North Cypress Reservoir was proposed to be located along Longenbaugh Road and Katy-Hockley Road partially in Waller County and partially in Harris County. See map below.

Key statistics about the proposed Katy-Hockley North Cypress Reservoir are provided below:

• Drainage Area:                                             ~100 square miles (estimated)
• Site Area:                                                     7,400 acres
• Maximum Berm Height:                                8 feet
• Storage Volume:                                           26,500 acre-feet
• Peak Water Surface Elevation:                     167 feet above mean sea level
• Discharge Rate:                                            7,300 cubic feet per second
• Benefit to Cost Ratio:                                    0.89

The proposed Katy-Hockley North Cypress Reservoir would be designed to capture stormwater that overflows the Cypress Creek channel and floodplain and would otherwise flow into the Addicks Reservoir.  After capture and detention, the Katy-Hockley North Cypress Reservoir would release the water to both to Cypress Creek and to Bear Creek at controlled rates.

Implementation Questions

Here are some questions I think we should be asking before we decide to invest in any of these or other proposed “third reservoir” ideas:

1. How many existing homes and structures will have a reduced risk of inundation as a result of the project?
2. What amount of risk reduction will be achieved for existing homes and structures?
3. What will the post-project risk of inundation be for existing homes and structures?
4. What are the pre-project and post-project risk of controlled, high flow releases from Addicks and Barker Reservoirs?
5. What would the inundation risk be for future homes and structures in the areas upstream of the reservoirs?
6. What would the inundation risk be for future homes and structures in the areas downstream of the reservoirs?
7. How much land would be removed from potential development or prairie conservation?

If you’ve heard of any other “third reservoir” ideas, please tell us about them in the comment section below.

On April 5, 2018, the Greater Houston Flood Mitigation Consortium released Edition 1 of their Executive Summary report.  The report provides “information relevant to the local, state and federal investments being discussed for flood mitigation in Harris County.” The report also “summarizes the strategies that are in the Houston area’s toolbox and focuses on specific challenges and a variety of conclusions about how best to address both strategies and tactics.”

The report is 64 pages long, with a light gray font that is eye-strainingly small if printed out in hard copy format.  I’d suggest reviewing the report for more details, but don’t print it out. You should review the PDF report in digital format with a 150% zoom enabled.

This post will provide a few of my thoughts and reactions to the material in the report.  This should not be considered a summary of the report. For that, I’d suggest reading the report’s Section 6.0 – Conclusions.

Storm Surge: It was noteworthy that consideration of storm surge was excluded from the consortium’s work effort and the report. While the risk of storm surge is certainly much less than 1% per year, the negative consequences of a worst-case surge are very large.

Political Will: The report mentions the role of “political will” in planning and responding to flood risks. Someone involved in regional water planning once called me on my use of that phrase and since then I’ve tried to avoid using the term.  With a bit of online research, one can see that there is not a good definition of what it is. One good one I found suggests that it consists of three elements: (1) Opinion, informed by both knowledge of the issue and how the issue is framed; (2) Intensity, the depth and strength of the viewpoints held; and (3) Salience, the degree of importance of the issue and how passionate stakeholders might be about it.  .

Pot Shots at Developers: The report takes a few (perhaps) unwarranted shots at developers.  For example: “… there are instances when developers have found ways to work around the [regulatory] system.” (p. 2)  To support this statement I’d like to see a more detailed description of what situation was actually observed and how the circumstances were handled. At this point I pretty much expect mainstream media to rehash the narrative that development is to blame for all flooding and that new development doesn’t include mitigation, but I would have expected the Consortium report to avoid restating any portion of that narrative.

Principles: I support pretty much all of the principals presented in the report. A focus on human impacts over property impacts makes sense. Collaboratively and inclusively determining what level of risk we are willing to accept is key (because it’s not physically possible to achieve a zero risk level and we can’t afford to achieve an extremely low risk level). Collaboration and coordination across watersheds should be undertaken.  Risk communication is very important.  Using both structural and non-structural strategies should be used. We should implement solutions at different scales. Preserving and restoring ecosystems will be helpful. Science-based decision-making is preferable.  Learn from other regions and nations. Understand the network relationships and that flooding is connected to other concerns. The only principle that gives me pause is the call for limiting new development “where necessary to mitigate downstream flooding and keep people and property out of harm’s way.”  My main concern about this relates to private property rights and our collective ability to pay current landowners for the use of their property (to avoid a constitutional takings claim).

Offsite Flows: The report incorrectly states that land development engineers “typically focus on mitigating the runoff generated by their development project, and as such, flows entering onto their site from other sources may not be considered in their design analysis.”  This is just not true.  Offsite flows are always considered and engineers cannot obtain a development permit without addressing offsite flows. Ok, maybe, if the development site is surrounded by existing development that conveys water away from the subject site, we might not consider offsite flows; but in that case, why would we?

Flood Warning Systems: I strongly agree and support this idea. The report provides a good overview of the issues and the emerging capabilities.

Green Infrastructure: The report provides a good overview of these ideas along with rational and appropriate caveats about our topography and soils so that the reader might understand that green infrastructure approaches are not a silver bullet.  As I’ve written previously, we need to do more field infiltration testing to learn more about what is possible with soil amendments, deep root vegetation, and actual field conditions.

Sea Level Rise and Climate Change: Both are mentioned, contrary to some accounts of this report that suggested the report is silent on these topics.

Clarity About a Third Reservoir: The report does a good job of outlining the potential benefits and costs of any potential third reservoir (depending upon its design intent).  Many have called for its construction without being detailed about its purpose. Is it to mitigate new development flows? Is it to reduce the probability and frequency of Addicks and Barker overflows?  Is it to reduce the frequency of Cypress Creek overflows?  Is it to preserve the Katy Prairie?

Watershed Discussions: The report includes some great, factual, and thoughtful discussion about all of the major watersheds in the Harris County region. You should definitely read about the watershed in which you reside. There are also some great details about our level of investment, population stats, and the level of risk exposure in each watershed that should be more widely known.

Probabilistic Flood Analysis: I like the idea of using a Monte-Carlo or statistical method of estimating flood risk.  This would be in place of deterministically modeling each storm sewer, swale, channel, or bayou.  I wonder, however, if the various federal and state governing organizations (think: Federal Emergency Management Agency and National Flood Insurance Program), as well as lenders and reinsurance companies, would accept that type of risk mapping product?

Conclusions: Section 6 of the report is only five pages long. If you don’t have time to read through the entire document I would encourage you to read the conclusions.  Some very good thoughts and ideas for all Houston-area stakeholders to consider.