Atlas 14 Updates Rainfall Frequency Estimates Developed in 1960s
Developers must now design detention and storm sewers around rainfall rates that increase 16-32% compared to the old standards for Harris County.
Data included in Atlas 14:
Replaces rainfall-depth information used since the 1960s
Provides estimates of the depth of rainfall for average recurrence intervals of 1 year through 1,000 years, and durations from 5 minutes to 60 days.
NOAA collected this data in Texas through December 2017, which includes rainfall from Hurricane Harvey.
New Atlas-14 Rainfall Frequency Estimates for the Lake Houston Area
Floodplain, Detention & Fill Restrictions
The amended policy manual adopts the increased precipitation rates. It also specifies more rigorous criteria for detention basins and fill within the floodplain.
Amendments anticipate that the future Atlas-14 1% (100-year) floodplain will equal the current 0.2% (500-year) floodplain.
Harris County Flood Control District
Therefore, these amendments are considered to be interim and will be reevaluated once new floodplains have been produced as part of HCFCD’s Modeling Assessment and Awareness Project (MAAPnext) in late 2021. You can find more information on MAAPnext at www.maapnext.org.
Zero Net Fill
The old guidelines prohibited developers from adding fill only within the 100-year floodplain. Now they’re prohibited from adding fill within the 500-year floodplain, too. The policy is called “zero net fill.” It means developers cannot bring fill into the floodplains. They can, however, excavate fill from one part of their property and use it to build up another part of their property.
Under new guidelines, developers cannot bring fill into either the 100-year or 500-year floodplains.
For a 20-acre development, the average volume of stormwater within detention basins will increase by about 20%, or about 32,500 additional gallons per acre.
Effort to Harmonize Floodplain Regs with Neighbors’
Guidelines for floodplain development can bewilder even professionals. Overlapping jurisdictions often have different guidelines. And guidelines often change, as Houston’s just did. Houston now manages the 100-year and 500-year floodplains differently. Cities also have building codes that include more requirements.
Site of the proposed new marina and high rise development. Shot from over the West Fork shortly after Harvey. Note sand deposited by Harvey. 25 and 50-story high-rises would be built on the narrow strip between the lake and the Barrington at the top of frame.
Overview
People ARE generally allowed to build and place fill in floodplains. However, they must follow local floodplain guidelines and obtain permits that restrict what they can do. They must also submit environmental surveys, mitigate wetlands, and provide hydrologic and hydraulic studies. In Houston, they may move earth from one location to another within a floodplain, but not add to the total volume. The general rule of thumb: zero negative impact on the conveyance of the river.
If a development destroys wetlands, wetland credits must be purchased from a mitigation bank. Mitigation banks place conservation easements on some of our most valuable wetlands. By helping to finance conservation of those areas, destruction of less valuable wetlands elsewhere may be permitted. Generally but not always, the mitigation credits must be within the same watershed. However, this is not always the case. Extenuating circumstances may exist.
KSA once considered placing East End Park in a mitigation bank as a way to help finance its long range parks plan. The conservation easement would ensure that the character of the park never changed. And the money raised would have provided needed improvements to other parks at no cost to residents.
Federal Guidelines and How They Relate to Local
FEMA establishes minimum standards for a community to enroll in the National Flood Insurance Program (NFIP). By enrolling and administering floodplain regulations, it allows their residents the opportunity to purchase Flood Insurance through the NFIP. You must at least build at FEMA’s base flood elevation (BFE). But communities can and do set higher standards. And each may have different guidelines.
Engineers and regulators often talk about “freeboard factors.” Freeboard, a nautical term, means “the height of a ships side between the waterline and the deck.” In a flooding context, freeboard means minimum elevation above the BFE. You often see it described as “BFE + 1 ft.” Or 2 feet. Or X feet. Think of it as a safety margin. Any freeboard above the BFE is considered a local community’s higher standard.
To provide a context, below are links to some of the floodplain management orders/ordinances.
Note Chapters 9 and 13. They changed on September 1, 2018. Changes address building code issues for FEMA X zones. Zone X includes the 500 year flood plain. Many such areas flooded during Harvey.
If a development affects a major waterway like the San Jacinto River, its wetlands, its flow, or endangered wildlife, the Army Corps will also review studies submitted as part of the permitting process. They would look at applications from the point of view of the EPA and Clean Water Act, especially Section 404.Section 404 of the Clean Water Act (CWA) establishes a program to regulate the discharge of dredged or fill material into waters of the United States, including wetlands. … For most discharges that will have only minimal adverse effects, a general permit may be suitable. This is the major focus of the permitting process now underway for the high-rise development in Kingwood.
TCEQ
The Clean Water Act also contains a section 401. It specifically focuses on how States and Tribes can use their water quality standards in Section 401 certifications to protect wetlands. States and Tribes can review and approve, condition, or deny any Federal permits or licenses that may result in a discharge to waters of United States within their borders, including wetlands. States and Tribes make their decisions to deny, certify, or condition permits or licenses primarily by ensuring the activity will comply with applicable water quality standards. In addition, States and Tribes look at whether the activity will violate effluent limitations, new source performance standards, toxic pollutants restrictions and other water resource requirements of State or Tribal law.
Jurisdictional Divides
The Houston ordinance only applies to Houston’s jurisdiction. Houston does not influence neighbors and cannot control or force their policies on other jurisdictions. That is important since Kingwood is surrounded by Humble, unincorporated Harris County (Atascocita and Huffman), and unincorporated Montgomery County.
The Key
Understand that if a developer/individual meets the requirements identified in the floodplain ordinance(s), they can develop in the floodplain (including the floodway). Floodplain administrators must follow the law. However, they try to discourage dangerous floodplain development by “working to rule.” By strictly following all rules with no wiggle room, floodplain administrators can drag permitting processes out. A knowledgeable floodplain administrator can find problems with plans, surveys, and engineering reports for years. By requesting revisions, they can make life so difficult for applicants that it affects the economics of their developments. Eventually they may decide that a project falls into that great black box called “too hard to do,” and walk away.
Words of Wisdom
A regulator told me today that the more people who protest a permit, the harder they are to ignore.
If you have concerns about the high rise development in Kingwood, make sure you register them with the Army Corps (which is currently reviewing the permitting from a CWA 404 perspective). The deadline: January 29.
Comments and requests for additional information should reference USACE file number, SWG-2016-00384, and should be submitted to:
Evaluation Branch, North Unit
Regulatory Division, CESWG-RD-E
U.S. Army Corps of Engineers
P.O. Box 1229
Galveston, Texas 77553-1229
409-766-3869 Phone
409-766-6301 Fax
swg_public_notice@usace.army.mil
Posted By Bob Rehak on January 9, 2019
498 Days Since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/03/Harvey-SanJac_179-e1546828712317.jpg?fit=1500%2C1000&ssl=110001500adminadmin2019-01-06 21:33:032019-01-13 12:35:07Guide to Lake Houston Area Floodplain Regulations
The developer of a proposed new high-rise resort in Kingwood plans to develop the marina portion in an area that was once the riverbed of the San Jacinto west fork.
Aerial photos taken in 1943 clearly show the outline of an old meander about .4 miles north of the current riverbed.
1943 aerial photo. Note feint outline of old riverbed above the current river.
Google Earth lets users trace a path and then save it, like I have with this orange line.
Creating an outline of the path allows you to scroll forward in time within Google Earth (see image below).
Here is the same path superimposed over current conditions.
Plans call for marina high rises along orange path just north of lake below eastern edge of Barrington.The Marina would be developed in the old river bed of the San Jacinto.
Photo of proposed marina site next to River Grove Park. The giant sand bar in the foreground of this photo taken after Harvey has mostly been dredged by the Army Corps. However, it’s appearance almost overnight during Harvey contributed to the flooding of 650 homes above the drainage ditch (center left). Future development in this floodplain would likely make flooding worse.
Dangers of Building in Old Stream and Riverbeds
During major floods, water often follows these old streams and riverbeds. Many neighborhoods in Houston discovered this danger during Harvey. Former Harris County Judge Ed Emmett often questioned the wisdom of such developments because of their susceptibility to flooding – even after mitigation.
Here are two examples that show such developments encroaching on waterways and separating them from their floodplains. In the first example, the waterway was obliterated. In the second, White Oak Bayou, the waterway still exists. However, the flood plain has been developed. Despite mitigation efforts during development, the neighborhoods around White Oak Bayou have suffered severe and repeated flooding.
Why Do We Continue to Develop Flood Plains?
This brochure, Why We Continue to Develop Floodplains: Examining the Disincentives for Conservation in Federal Policy, is a must-read for anyone who wants to understand the financial logic behind developments like this one. A group called Earth Economics developed it. Zachary Christin, Project Director for Earth Economics, and Michael Kline, from the Vermont Department of Environmental Conservation, authored it with support from the Kresge Foundation. This report investigates whether current federal policy is structured to prevent future flood damage or if incentives lead to further floodplain development.
The basic premise may rub many Texans the wrong way, but you should still read it. “Flood risk management,” the authors argue, “seeks to enable communities to live nearby by controlling rivers with levee systems and other structures. This false sense of protection places families and infrastructure at risk in a climate that is changing beyond our capacity to maintain protections against its effects. Rather than attempting to control our country’s powerful rivers, we should instead control how and where we allow human activities.”
Confining streams, they argue, merely shifts flood risk downstream. The authors explore the benefits and the natural protective qualities of healthy, functional floodplains. They then discuss the causes of floodplain destruction and investigate the policies that further incentivize their development. Finally, they outline paths forward to create new floodplain policy. You may disagree with the premise. But it contains many powerful observations and statistics.
As always, these represent my opinions on matters of public policy. They are protected by the First Amendment of the U.S. Constitution and the Anti-SLAPP statute of the Great State of Texas.
Posted by Bob Rehak on January 2, 2019
491 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/01/AncientMeander.jpg?fit=1500%2C1023&ssl=110231500adminadmin2019-01-02 19:38:332019-01-13 12:36:05Developer Plans to Build High-Rise Resort in Old Riverbed
