Les inondations récurrentes de Houston, une fatalité ?

L'ouragan Harvey est maintenant en cours de dissipation et c'est au tour d'Irma de pointer le bout de son nez, avec des prévisions dignes de madame Irma (sic) :

• Hurricane Irma, also known as Typhoon Irma, in the Philippines known as Typhoon Isang, and in the Indian ocean known Very Severe Cyclonic Storm Megh, was the longest lasting tropical cyclone ever recorded, as well as the strongest ever recorded. Irma, having developed in the Atlantic on September 18, 2017 before finally dissipating on November 4, 2017, lasted a record breaking 48 days, shattering the previous record held by Hurricane John in 1994. Irma as a Typhoon also obtained a peak of 868mb, making Irma the strongest tropical cyclone ever recorded in any basin.

Plus sérieusement, voici quelques indications par l'image :

Updated 11:00 am, Sat September 2, 2017, source cnn/storm-tracker

earth.nullschool.net

Il est peu probable qu'Irma touche le sud des Etats-Unis, bien qu'il ne faille jamais dire jamais.

Harvey aura donc fait des dégâts considérables, surtout sur Houston et sa périphérie, mais on peut se poser la question de savoir si ces dégâts sont vraiment imputables à l'ouragan ou si d'autres causes ne sont pas à avancer ; et en investiguant un peu on s'aperçoit que les Texans sont "un peu" responsables de leurs malheurs, ou pour le dire plus crûment, ils n'ont eu que ce qu'ils méritaient !

Quand je dis "ils" je n'inclus pas en vérité tout le monde, car il y a des Houstoniens qui se préoccupent depuis longtemps de la situation de leur ville et qui le font savoir, de toute évidence sans grand effet sur les "élites" qui décident de leur "bien-être".

Je n'ai pas eu le temps de tout lire, et je n'aurai pas le temps de traduire, car il y a une abondante littérature et je suis obligé d'effectuer un choix forcément réducteur, mais j'espère suffisamment significatif, sous forme de simples extraits ; je laisse à chacun le soin d'aller plus loin, les liens sont disponibles, rien n'est caché.

J'ai sélectionné deux sites :

• http://www.savebuffalobayou.org/
• http://drainagecoalition.com/
  

Sur le premier site Save Buffalo Bayou, qui offre la possibilité de rechercher un mot clé, j'ai d'abord tapé "1935" puis "flood".

recherche mot clé "1935"

http://www.savebuffalobayou.org/?page_id=3580
Engineers Caused the 1935 Flood that Led to Creation of Flood Control District (5/03/2017)

• Bloom and Stagner’s description of the 1935 flood that led to the creation of the flood control district is in error. In fact, the catastrophic flooding that occurred in downtown Houston was the result of faulty engineering. A 1937 report commissioned by the Texas legislature found that the sole cause of the flooding was a badly designed bridge – the Magnolia Bridge, built by the Magnolia Ice and Brewing Company in 1912. The bridge’s base was too narrow and caused the rain-swollen Buffalo Bayou to back up rapidly into downtown.
• Furthermore, the Katy prairie at that time was not “undeveloped,” as described by Bloom and Stagner as well as other advocates for the flood control district. Most if not all of the native deep-rooted tallgrass prairie in the Katy area west of Houston, source of Buffalo Bayou, was by then agricultural land, which has far less ability to hold and absorb rainwater.
• Bloom and Stagner state that tallgrass prairie cannot “prevent flooding.” No one suggests that preservation or restoration of native prairies, forests, and wetlands, including riparian wetlands along our bayous and streams, will “prevent flooding.” It is quite obvious that not even engineers can prevent flooding. The goal is to reduce flooding risk and protect our vital natural drainage and water-cleansing systems.
• We support stopping storm water before it gets into our local streams. Slow it down, spread it out, soak it in. That approach, working with nature, is cheaper and more effective, better for us and environment, and the most enlightened approach to floodplain management.
• The National Oceanic and Atmospheric Administration study cited by Bloom and Stagner finding no increase in the frequency of extreme weather events may not present the whole picture. State Climatologist Dr. John Nielsen-Gammon says that climate models “predict a long-term upward trend in extreme rainfall events and temperatures in Texas.” Dr. Phil Bedient, professor of engineering and director of the Center for Severe Storm Prediction, Education and Evacuation from Disasters (SSPEED) at Rice University, points out that the Houston region is in fact experiencing more frequent and more intense rainfall events, leading to more damaging flooding.
• In any case, Bloom and Stagner cannot have it both ways. Houston is obviously flooding in places it rarely if ever flooded before, and flooding more severely more often. Either more intensive rainfall is causing flooding, i.e. it’s just a lot of rain and “not man-made flooding,” according to Bloom and Stagner (and former flood control director Mike Talbott). Or if extreme weather events are not increasing, according to the NOAA study cited by Bloom and Stagner, something else – something not natural but man-made — must be causing more frequent and damaging flooding

Apparemment il y a un "point de vue côté ingénieurs" et un "point de vue côté habitants", et les deux sont de toute évidence contradictoires...Les ingénieurs en question (Bloom and Stagner) affirmaient notamment :

• The uncomfortable fact for most people is that the Houston region is flood prone and engineering and infrastructure solutions will never reduce or prevent extreme rainfall events. Large rainfall amounts, especially those that exceed our storm design, will always occur and will always result in flooding. This is not “man-made flooding.”

Les avis sont donc partagés.

http://www.savebuffalobayou.org/?p=3583
Engineers Caused the Flood That Led to Creation of Flood Control District (6/03/2017)

• According to this point of view [celui de Bloom and Stagner], our native tallgrass prairie and its associated wetlands are hardly better than concrete when it comes to slowing and absorbing rainwater. These deep-rooted grassland prairies, with water-absorbing root systems that can reach 12-15 feet into the ground or more, once existed around and upstream of Buffalo Bayou, in Katy, west of Houston, for instance, source of Buffalo Bayou, as well as up and down the coastal plain. Practical people are trying to preserve and restore what remains.
• In support of their argument, Bloom and Stagner summon up a point commonly made by members of the local engineering community: that the 1935 flood on Buffalo Bayou that devastated downtown Houston and led to the creation of the Harris County Flood Control District happened even though the Katy Prairie way upstream was then a big natural tallgrass prairie.
• This argument is wrong on two points. Read why in this fact-based response by Save Buffalo Bayou to an “Engineers’ View” published as a comment in the Tribune’s TribTalk.

https://houstonmaritime.org/learn/hmm-lecture-series?id=176
Buffalo bayou flooding: A Historical perspective (11/10/2016)

• The recent flooding in Houston has reminded us that the city and its residents are subject to the effects of high water and flooding on Buffalo Bayou and other streams in Houston. From the earliest days of the city, Houstonians have had to deal with rainfall and the high water conditions it produces. This presentation will provide a historical perspective to those conditions. Visitors will gain an appreciation for why Houston is known as the “Bayou City.”  

Il s'agissait d'une conférence dont malheureusement aucun compte rendu n'est apparent sur le site.

http://www.savebuffalobayou.org/?page_id=2851
The Flood Czar Answers His Own Phone (12/07/2016)

• The soft-spoken Costello, a civil engineer, former member of the Houston City Council (serving six years), former president and current board member of the Memorial Park Conservancy, and former candidate for mayor of Houston, was speaking at a meeting of the Briar Forest Super Neighborhood in west Houston a few weeks ago. Buffalo Bayou runs through the Briar Forest Super Neighborhood.
• [...] Costello answers his own phone and emails himself. He has no staff. Apparently he has no funds or budget. (He also said in a later email exchange that he wasn’t sure where the funds for his salary were coming from and didn’t answer how much he was being paid.) Yet he has been bravely handing out his card, offering his cell phone number and email to myriad people in a city drowning in outrage and misery over increasing and repeated flooding, lost homes, cars, property, savings, and lives.
• We know that Houston has a flooding problem, and that flood damages are increasing, despite the hundreds of millions if not billions of federal, county, and city tax dollars being spent on flood control and drainage.
• In Fiscal Year 2015 the overall budget for the Harris County Flood Control District was $66 million for maintenance and operations and $158 million for Capital Improvement Projects, a total of $224 million, which includes some federal funds. The District’s FY 2016-17 Capital Improvement budget is $66 million. The flood control district employs 341 full-time employees [à mettre en regard des dizaines de milliards de dollars que va coûter Harvey...]
• Drainage problems are one of the three types of urban flooding threats listed by Costello in his talks and panel discussions, and drainage is the issue that he is focusing on, he says. “A lot of houses throughout the city flooded from poor drainage infrastructure,” said Costello.
• The other two flooding threats, as described by Costello, are riverine (overflowing streams) and tropical events like hurricanes. The Harris County Flood Control District, often working with and funded in part through the US Army Corps of Engineers, is responsible for dealing with riverine flooding.
• There are also badly built bridges that cause rushing floodwater to back up. A bridge over Buffalo Bayou downtown was a major cause of the catastrophic flooding of downtown Houston in 1935 that led to the creation of the flood control district. The flood control district’s controversial and much-delayed project known as Project Brays is replacing or modifying 30 bridges on Brays Bayou.

On voit donc que les moyens mis en place sont insignifiants ; les budgets sont ridicules en comparaison des dégâts causés, notamment par le dernier en date, Harvey ; par ailleurs rien, ou très peu, n'est fait pour véritablement s'attaquer aux problèmes auxquels Houston est confrontée.

http://www.savebuffalobayou.org/?page_id=2669
Dammed If They Do, Dammed If They Don’t (26/05/2016)

• It had taken only a little more than twenty-four hours for the rains that began on April 18 to fill the vast flood control reservoirs in west Houston with a record amount of water: a total of more than 206,000 acre feet, a massive amount of water. Imagine 206,000 acres covered in a foot of water. Enough to cover more than eight times the acreage of both reservoirs to a depth of one foot. That much water would take an estimated four weeks to drain, according to reports at the time.
• Not since 1992 had the water been so high behind the two federal dams that protect the city of Houston from catastrophic flooding downstream on Buffalo Bayou. In fact, until recently, most Houstonians, even those who grew up here, were probably unaware or only vaguely aware that there are dams that prevent the center of the city, including downtown, from massive flooding.
• The original 1940 plan was not just for two dams on Buffalo Bayou, however. There was also to be a dam on White Oak Bayou and a levee on Cypress Creek to the north, where there was major flooding on April 18. There were also to be two major canals: one on the north feeding into the San Jacinto River and another on the south that emptied into Galveston Bay. The plan was ignored, wisely or not, as was a much earlier 1913 plan created for the Houston Park Commission by landscape architect Arthur Comey (see page 53) calling for woodland parks along all the bayous extending for some four to six miles through the city.
• The dams enabled development close to the bayou. The charming meanders and majestic trees that naturally flourish along the banks attracted developers who built residential subdivisions, as well as office buildings, highrise towers, and parking lots. Development on the bayou and in the prairie upstream and downstream has also increased impermeable surface, causing faster, more concentrated runoff into the reservoirs and into the bayou. (Flooding below the dams now happens because of that fast, heavy runoff from streets, buildings, parking lots, and other paved or hardened surfaces. And mostly it’s flooding that happens before the stormwater gets into the bayou.)

Ainsi, assez ironiquement, la construction des deux retenues d'eau censées régler, ou du moins atténuer, le problème des inondations, a en fait accru celui-ci en favorisant des constructions et du bétonnage supplémentaires "en raison" de l'attractivité nouvelle des lieux !

recherche mot clé "flood" (201 occurrences...)

http://www.savebuffalobayou.org/?p=3953
Free Lecture: Houston’s Self-Inflicted Flooding We’re Number One! (19/06/2017)

• Why does Houston have such awful flooding problems? And why do they seem to be getting worse?
• A citizens’ group dedicated to reducing preventable flooding caused by development in the Houston region is presenting one of the leading experts on the subject at a free public talk Tuesday, June 20.
• Brody also agrees with Save Buffalo Bayou that the current public policy of widening and deepening (and destroying) our urban streams to handle increased stormwater flow is outdated and ineffective. “We can solve the problems or treat the symptoms,” says Brody. Widening and deepening our bayous is just treating the symptoms, which will only get worse with increased development, failure to enforce stormwater detention requirements, and policies that emphasize costly engineering solutions like bigger drain pipes that collect and shunt more and more rain runoff into our streams faster and faster.
• Leading experts nationally agree that the emphasis should be on slowing down, spreading out and soaking in stormwater before it hits our streams. Unlike other major cities such as Philadelphia and New York, flood-prone Houston has no plan for managing stormwater through Green Infrastructure, which typically brings greater benefits – including more parks and green space – at far less cost.
• The Harris County Flood Control District project opposed by Save Buffalo Bayou would spend some $12 million to raze the trees, dig up, channelize and shorten one of the last natural stretches of Buffalo Bayou in order to send more stormwater downstream faster, a practice that even the US Army Corps of Engineers acknowledges causes more flooding and erosion downstream. (See Buffalo Bayou Partnership 2001 Master Plan Project, p. 18.)

Il semblerait donc que l'essentiel des moyens mis en oeuvre pour soi-disant "régler le problème" n'aurait en réalité d'autre effet que d'amplifier celui-ci !

http://www.savebuffalobayou.org/?p=3534
Petition to End Avoidable Flooding Citizens Call for Regional Oversight Based on Science, Transparency, and Enforcement (17/01/2017)

• A Houston group called Citizens Solutions to Flooding is circulating a petition calling for the creation of a long-overdue Houston-Galveston regional body to ensure that new construction and development does not increase flooding.
• The petition focuses on the inadequacy and lack of enforcement of current regulations regarding stormwater drainage and detention. It calls for transparency in the permitting process and financial incentives for property owners to retrofit properties to conform to more effective standards for controlling stormwater running off impervious surface.
• Houston’s natural tendency to flood has been greatly worsened by uncontrolled development and the proliferation of hard surface like parking lots, building rooftops, and roadways that rapidly collect and concentrate rainwater rather than slowing, absorbing, and dispersing it.

Il est peut-être encore temps de signer la pétition...

http://www.savebuffalobayou.org/?p=3182

Buffalo Bayou Flooding: A Historical Perspective (7/10/2016)

• Louis Aulbach, author of the definitive guide to Buffalo Bayou, will speak on Tuesday, Oct. 11, on the history of flooding in Buffalo Bayou. The free lecture is from 7 to 8 p.m. at the Houston Maritime Museum, 2204 Dorrington St.

  

  Downtown Houston during the 1935 flood and before the construction of the Addicks and Barker dams.

   

Malheureusement toujours aucun compte rendu de la présentation.

Le deuxième site est RESIDENTS AGAINST FLOODING

http://drainagecoalition.com/?p=935
Don’t blame Mother Nature for flooding. Blame City Council. (20/04/2016)

• The disasters are predictable. Why aren’t we preventing them?
• Man-made, preventable flooding has surged dirty, sewage-ridden water through Houston living rooms three times now in seven years, yet city government fails to prevent these recurring emergencies.
• Right now, too many real-estate developments do not detain storm water run-off from their new construction, and instead allow it to flow downstream into other neighborhoods, into people’s homes. This new development is  responsible for unnecessary flooding of neighborhoods that previously weren’t flood plains, weren’t prone to flooding. That new development is also responsible for flood insurance rising 100 to 200 percent (before the Tax Day flood) in these non-flood plains.
• City government is allowing this to happen. Developers use loopholes and grandfathering to avoid doing what the city’s laws require them to do. Is it ethical to allow a new office building to flood an entire neighborhood even if a loophole makes it legal?
• For seven years Houston homeowners have begged and pleaded with the mayor (previous and present) and City Council members to treat man-made flooding as urgent, as if it were a deadly fire to put out in a hurry. Yet despite hundreds of emails, calls, meetings, petitions from homeowners’ associations (at least 18), Super Neighborhoods, civic associations, and person-after-exhausted-person speaking at City Hall, there is more talk about bike trails and recycling than critical, focused action to address our flooding.
• Underhanded, unethical things are being done to keep big developers happy while homeowners suffer needlessly. That’s why a nonprofit group called Residents Against Flooding was formed in 2009: to show the Houston-area public that  the cause of our troubles isn’t Mother Nature, but rather our city government’s failure to act.

Mère Nature n'est peut-être pas à mettre en cause, mais quand même, elle a un peu aidé cette fois avec Harvey, non ? Avec Harvey et tous les émetteurs de CO2 qui lui ont permis d'être "un peu plus puissant" qu'il ne l'aurait été "naturellement".


http://drainagecoalition.com/?p=187
Can We Stop Houston Flooding? (22/09/2012)

• Our issues with Grandfathering are: unwarranted variances have been granted to builders, such as elevating property with no consideration of sheet flow obstruction or compensating detention; proper detention simply wasn’t installed; the land was developed prior to annexation by the City; or, for any number of other reasons, adequate detention and/or site drainage wasn’t installed. Once built, these properties are forever Grandfathered and new ones are added every year, so that the floodplain will continue growing until Grandfathering is removed from City Design Manuals.

Je me suis demandé ce que pouvait bien vouloir dire "Grandfathering" sachant qu'un "grandfather" est un grand-père, j'ai la réponse je pense ici avec wikipedia :

• A grandfather clause (or grandfather policy) is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases.

Le mot "provision" signifie dans ce cas une clause ou une disposition d'un contrat ; donc une "clause grand-père" est en quelque sorte une disposition n'ayant pas d'effet rétroactif, à double effet donc, une partie continuant à s'appliquer "comme par le passé du temps de grand-père", une autre partie s'appliquant pour les petits-enfants...

• Each year that the 100-year floodplain grows, Houston’s viability as a good location for new businesses is diminished. Moreover, the cost to residents increases in the form of diminishing home values, increased insurance rates, or actual flood damage to property. Our practice of using streets as drainage channels and neighborhoods as detention areas routinely brings the City to a standstill with untold property damage and work hours lost. 

http://drainagecoalition.com/?p=960
Man-made Flooding in Greenspoint (25/04/2016)

• Below is a map showing where the apartments flooded in the Greenspoint area during the April 18, 2016 flood.  Note that all of the apartments that flooded are in the 100-year floodplain for Green’s Bayou and some of the apartments are actually within the floodway – the no build zone set up along bayous and streams.  While we understand that some of these apartments were built before the floodway ordinance, surely the 100-year floodplain was in place.  Look closely and you’ll see that there are no detention ponds associated with most, if not all, of these apartments.  Look around Houston.  How many apartments are built in areas close to bayous?  How many have installed detention?  Did they pay a fee in lieu of detention?  Was that fee used to build detention within the watershed where they were built or in some other unrelated watershed?  Were any of the residents of these apartments aware that they were in the floodway or the 100-year floodplain for Green’s Bayou?  Could the 1800 apartments here that flooded be called a man-made disaster?  You bet your wet a$$ they can!!

Yellow dots are the apartments that flooded in Greenpoint.

A noter que "floodplain" signifie lit majeur, c'est-à-dire plaine d'inondation ; un "100-year floodplain" ne veut pas dire qu'il y a une inondation par siècle dans ce lit majeur, mais que chaque année il y a une chance sur cent pour qu'il y en ait une ; c'est comme jouer à pile ou face, chaque fois qu'on jette la pièce en l'air, même au bout de plusieurs milliards de jets, il y a toujours 50% de chance que la pièce tombe sur pile et 50% de chance pour qu'elle tombe sur face, ce qui ne veut pas dire que la pièce ne va jamais tomber deux, trois ou davantage de fois de suite sur le même côté...Il est donc possible que dans un proche avenir la "100-year floodplain" devienne une "50-year floodplain" ou même une "<50-year floodplain"...

*****

Mon billet est forcément incomplet, j'imagine que j'ai dû rater bien d'autres articles intéressants, mais une idée générale se dégage tout de même, à savoir que l'on connaît depuis très longtemps les problèmes de Houston mais que pas grand chose n'a vraiment été tenté pour y faire face.

L'argent (i.e. la cupidité et l'avidité humaines) semble être la cause principale des inondations à répétitions qu'a connues la ville de Houston, même avec Harvey qui sera peut-être le révélateur (je n'ose dire la goutte qui fait déborder le vase...) auprès de l'opinion publique américaine ; mais même cela n'est pas totalement sûr, le déni étant quelque chose de suffisamment bien ancré dans bien des têtes en charge de gérer le pays.

On remarquera que les articles cités ci-dessus sont relativement récents et semblaient annoncer la catastrophe actuelle ; mais il n'est pire sourd que celui qui ne veut rien entendre et pire aveugle que celui qui ne veut rien voir.