On October 3, 2022, the City of Houston announced an update of its 568-page Infrastructure Design Manual (IDM). The new IDM will govern all new construction within the jurisdiction of Houston after October 1.
Residents concerned about the possibility of new construction negatively affecting drainage should review it and related documents to make sure contractors adhere to requirements. At a minimum, neighbors should understand the outcomes that the City expects developers to achieve in case something goes wrong.
Chapter 9 addresses Stormwater Design and Water Quality Requirements. At a minimum, make sure you read Section 9-2, pages 183 and 184 of the PDF. The City lays out the high-level requirements and objectives for developer/contractors.
Goals Guiding Drainage Standards
Chapter 9 begins with several paragraphs that lay out the obligations of developers and contractors. I’ve condensed them for brevity below. See the original document for the exact wording.
9.1.02.A (1)
Drainage criteria for newly designed areas must provide protection from Structural Flooding during a 100-year storm event.
9.1.02.A (2)
Recognizing that each site has unique differences, the City may consider alternatives (pipe flow, overland sheet flow, and detention storage) that still achieve objectives.
9.1.02.B
Ponding in streets and roadside ditches of short duration is anticipated and designed to contribute to the overall drainage capacity of the system.
9.1.02.C
When rainfall events exceed the capacity of the storm sewer system, the additional runoff is intended to be conveyed or stored overland in a manner that reduces the threat of structural flooding.
All proposed New Development, Redevelopment, or Site Modifications shall not alter existing or natural overland flow patterns and shall not increase or redirect existing sheet flow to adjacent private or public property.
Where the existing sheet flow pattern is blocked by construction (i.e. raising the site elevation) of the Development, the sheet flow shall be re-routed within the developed property to return flow to original configuration or to the public right of way (ROW).
Except under special circumstances dictated by natural or existing drainage patterns no sheet flow from the developed property will be allowed to drain onto adjacent private property.
No impact will be allowed onto adjacent property.
9.1.02.C of CoH 2022 Infrastructure design manual
No sheet flow from the developed property may drain onto the adjacent ROW.
Any increased quantity discharge should only be discharged to the ROW at the approved point of connection (which have enough capacity to handle the discharged) via a subsurface internal drainage system.
Another tropical wave is moving into the Caribbean along the same track as Ian. As of Monday morning at 8 a.m., the National Hurricane Center gives it a 40% chance of developing within 5 days. Currently, the tropical wave is several hundred miles east of the Windward Islands and moving westward at 15-20mph. The NHC has designated this area of investigation as 91L.
Atlantic tropical waves and directions.Invest 91L is orange.
While Invest 91L looks fairly impressive on satellite images (see below), Jeff Lindner, Harris County meteorologist says, “There does not appear to be any closed low-level circulation yet. This wave should reach the eastern Caribbean Sea around mid-week and the western Caribbean by this weekend.”
91L is the storm north of the Guyanas and Suriname on the north coast of South America.
Says Lindner, “Conditions generally become favorable for development along the track of 91L, but when compared to Ian, model solutions are much more varied with development potential and also much more scattered. Some models take the storm into Central America, others predict it will track toward Puerto Rico and the Dominican Republic.
In the meantime, the eastern Pacific is fairly active. NHC is tracking three storms. Two are moving northwest parallel to the Mexican coast as a third – Hurricane Orlene moves inland near Mazatlán.
Mid- and high-level moisture from Orlene will stream across our area later in the week. However, our air is so dry right now that precipitation aloft will likely not reach the ground.
Glancing Blow from Frontal Boundary Later in Week
Lindner also predicts, “Toward the end of this week, moisture may return to Texas from the Gulf of Mexico ahead of a front that will drop into the eastern U.S. The front should only strike a glancing blow to Texas. Most of it will head more southeast toward the Tennessee Valley. So rainfall potential for Houston will remain low. Our dry pattern will likely continue.”
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/10/two_atl_5d0.png?fit=900%2C665&ssl=1665900adminadmin2022-10-03 11:33:412022-10-03 23:13:52NHC Gives 40% Chance of Formation to 91L Within 5 Days
How much value do you place on beauty? Serenity? Clean water where eagles fish? The experience of walking through the woods with your children and sitting on a quiet riverbank together? For many people, that means more than the risk of flooding. Until they flood.
Looking east along the San Jacinto West Fork toward Lake Houston from River Grove Park
Another study of 50 other studies systematically quantified the value of pathways between blue spaces and health benefits.
From “Mechanisms of Impact of Blue Spaces on Human Health: A Systematic Literature Review and Meta-Analysis” by Michail Georgiou, Gordon Morison, Niamh Smith, Zoë Tieges and Sebastien Chastin, Int. J. Environ. Res. Public Health, 2021, reproduced in Environmental Health Perspectives under a Creative Commons license.
It’s no secret that people like to live near water. It’s soothing. And it has both physical- and mental-health benefits. Until nature unleashes its fury. That’s when nature’s balance sheet gets confusing.
The Minus Side of the Ledger
Living near water comes with high risks…especially along the Gulf coast. Just watch the news these days. Witness the destruction and loss of life that Hurricane Ian brought to Florida last week.
Harken back to Hurricane Harvey. The storm flooded 16,000 homes and damaged 3,300 businesses in the Lake Houston Area. It also killed 13 people in Kingwood alone!
At the peak, we got 6.8″ of rainfall in ONE HOUR! The water on the West Fork reached more than 20 feet above flood stage!
Upstream development constantly heightens flood peaks which aren’t updated regularly.
Risky land is cheap, so demand is high.
Political lobbying makes Swiss cheese out of development and engineering standards to sustain profits and sales.
Buyers assume government regs protect them.
As a species, humans are notoriously poor predictors of risk. Just ask any casino owner.
But we have flood insurance, right? Wrong. Across Harris County during Harvey, 154,170 homes flooded, but only 36% of those had active flood insurance policies.
64% did not have flood insurance.
Harris County Flood Control District Final Harvey Report
The Most Sensible Solution
As a society, we seem to have settled on a solution to such problems. Whether we realize it or not, we:
Let people build what they want where they want most of the time.
Expect buyers to understand the risks and live with a level of risk they can afford.
Ask government to make things right after things go wrong.
But there’s a much simpler, more humane and cost-effective solution. It’s called conservation. And it’s based on an ancient wisdom – “An ounce of prevention is worth a pound of cure.”
Preserving that risky land near water keeps people out of harm’s way. It also reduces both damage and mitigation costs.
Turning that land into parks, nature preserves and recreational space lets everyone continue to enjoy it. And if we do need to build mitigation projects in the future, we will have the land. We won’t have to buy out whole neighborhoods and displace people to build a detention pond or expand a channel. And we’ll have a much healthier, happier society.
City of Houston Updates Infrastructure Design Manual
On October 3, 2022, the City of Houston announced an update of its 568-page Infrastructure Design Manual (IDM). The new IDM will govern all new construction within the jurisdiction of Houston after October 1.
Residents concerned about the possibility of new construction negatively affecting drainage should review it and related documents to make sure contractors adhere to requirements. At a minimum, neighbors should understand the outcomes that the City expects developers to achieve in case something goes wrong.
Chapter 9 addresses Stormwater Design and Water Quality Requirements. At a minimum, make sure you read Section 9-2, pages 183 and 184 of the PDF. The City lays out the high-level requirements and objectives for developer/contractors.
Goals Guiding Drainage Standards
Chapter 9 begins with several paragraphs that lay out the obligations of developers and contractors. I’ve condensed them for brevity below. See the original document for the exact wording.
9.1.02.A (1)
Drainage criteria for newly designed areas must provide protection from Structural Flooding during a 100-year storm event.
9.1.02.A (2)
Recognizing that each site has unique differences, the City may consider alternatives (pipe flow, overland sheet flow, and detention storage) that still achieve objectives.
9.1.02.B
Ponding in streets and roadside ditches of short duration is anticipated and designed to contribute to the overall drainage capacity of the system.
9.1.02.C
When rainfall events exceed the capacity of the storm sewer system, the additional runoff is intended to be conveyed or stored overland in a manner that reduces the threat of structural flooding.
All proposed New Development, Redevelopment, or Site Modifications shall not alter existing or natural overland flow patterns and shall not increase or redirect existing sheet flow to adjacent private or public property.
Where the existing sheet flow pattern is blocked by construction (i.e. raising the site elevation) of the Development, the sheet flow shall be re-routed within the developed property to return flow to original configuration or to the public right of way (ROW).
Except under special circumstances dictated by natural or existing drainage patterns no sheet flow from the developed property will be allowed to drain onto adjacent private property.
No sheet flow from the developed property may drain onto the adjacent ROW.
Any increased quantity discharge should only be discharged to the ROW at the approved point of connection (which have enough capacity to handle the discharged) via a subsurface internal drainage system.
How to Review Changes Quickly
The Houston Public Works Director signed the IDM Cover Letter & Executive Summary on July 1, 2022. The executive summary discusses updates made to all documents during the review cycle. The IDM Redlines and Construction Specifications Redlines are available for additional background. Redlines highlight changes from previous versions.
All of the content described here is accessible on the City’s Design and Construction Standards web page.
For more information, read HPW’s announcement here.
Posted by Bob Rehak on 10/4/2022
1862 Days since Hurricane Harvey
NHC Gives 40% Chance of Formation to 91L Within 5 Days
Another tropical wave is moving into the Caribbean along the same track as Ian. As of Monday morning at 8 a.m., the National Hurricane Center gives it a 40% chance of developing within 5 days. Currently, the tropical wave is several hundred miles east of the Windward Islands and moving westward at 15-20mph. The NHC has designated this area of investigation as 91L.
While Invest 91L looks fairly impressive on satellite images (see below), Jeff Lindner, Harris County meteorologist says, “There does not appear to be any closed low-level circulation yet. This wave should reach the eastern Caribbean Sea around mid-week and the western Caribbean by this weekend.”
Says Lindner, “Conditions generally become favorable for development along the track of 91L, but when compared to Ian, model solutions are much more varied with development potential and also much more scattered. Some models take the storm into Central America, others predict it will track toward Puerto Rico and the Dominican Republic.
For now, watch and wait.
Orlene Moves Inland Over Mexico
In the meantime, the eastern Pacific is fairly active. NHC is tracking three storms. Two are moving northwest parallel to the Mexican coast as a third – Hurricane Orlene moves inland near Mazatlán.
Mid- and high-level moisture from Orlene will stream across our area later in the week. However, our air is so dry right now that precipitation aloft will likely not reach the ground.
Glancing Blow from Frontal Boundary Later in Week
Lindner also predicts, “Toward the end of this week, moisture may return to Texas from the Gulf of Mexico ahead of a front that will drop into the eastern U.S. The front should only strike a glancing blow to Texas. Most of it will head more southeast toward the Tennessee Valley. So rainfall potential for Houston will remain low. Our dry pattern will likely continue.”
The National Weather Service Storm Prediction Center sees little to no severe threat.
Posted by Bob Rehak on 10/3/2022 at 11:30 am
1861 Days since Hurricane Harvey
Nature’s Confusing Balance Sheet
A headline in the New York Times last year said it all. “Our Love of Living Near Water Persists Despite the Dangers.”
How much value do you place on beauty? Serenity? Clean water where eagles fish? The experience of walking through the woods with your children and sitting on a quiet riverbank together? For many people, that means more than the risk of flooding. Until they flood.
In case you’re a pragmatist who scoffs at the value of visual poetry, a recent Canadian study found that people who lived within 250 meters of water had 12-17% lower mortality rates (excluding accidental causes) compared to those who lived farther away. The protective effects of living near water were found to be highest against deaths from stroke and respiratory-related causes.
Another study of 50 other studies systematically quantified the value of pathways between blue spaces and health benefits.
It’s no secret that people like to live near water. It’s soothing. And it has both physical- and mental-health benefits. Until nature unleashes its fury. That’s when nature’s balance sheet gets confusing.
The Minus Side of the Ledger
Living near water comes with high risks…especially along the Gulf coast. Just watch the news these days. Witness the destruction and loss of life that Hurricane Ian brought to Florida last week.
Remember the 30,000 homes on the Bolivar Peninsula destroyed by 22-foot storm surge during Hurricane Ike?
Harken back to Hurricane Harvey. The storm flooded 16,000 homes and damaged 3,300 businesses in the Lake Houston Area. It also killed 13 people in Kingwood alone!
At the peak, we got 6.8″ of rainfall in ONE HOUR! The water on the West Fork reached more than 20 feet above flood stage!
Mitigation has been as expensive as the damage. We’re spending hundreds of millions on dredging, spending $5 billion on more than 180 flood-bond projects, considering another $1.2 billion bond, trying to fund more than $3 billion in upstream detention projects, taking hundreds of millions out of transportation funds to address drainage issues, applying for $750 million in HUD mitigation funds, and looking at $30 billion worth of flood tunnels. Not to mention a $26 billion Ike Dike.
Recognizing Rewards but Not Risks
Why do we spend so much on repairs and mitigation? Because people build homes near water in places that aren’t safe.
Why? Because people want to live near water. And no one understands what the true risk is.
Why? Because:
As a species, humans are notoriously poor predictors of risk. Just ask any casino owner.
But we have flood insurance, right? Wrong. Across Harris County during Harvey, 154,170 homes flooded, but only 36% of those had active flood insurance policies.
The Most Sensible Solution
As a society, we seem to have settled on a solution to such problems. Whether we realize it or not, we:
But there’s a much simpler, more humane and cost-effective solution. It’s called conservation. And it’s based on an ancient wisdom – “An ounce of prevention is worth a pound of cure.”
Preserving that risky land near water keeps people out of harm’s way. It also reduces both damage and mitigation costs.
Turning that land into parks, nature preserves and recreational space lets everyone continue to enjoy it. And if we do need to build mitigation projects in the future, we will have the land. We won’t have to buy out whole neighborhoods and displace people to build a detention pond or expand a channel. And we’ll have a much healthier, happier society.
Posted by Bob Rehak on 10/2/22
1860 Days since Hurricane Harvey