In 2019, Montgomery County posted a minor update to a drainage criteria manual first published in 1989. However, in February 2024, the County published a draft of a comprehensive new update to the county’s drainage standards. The 124-page manual is a thorough rewrite that brings the County’s standards up to date and more in line with surrounding areas.
Some Major Revisions
Because the manual is targeted to engineers, it gets very complex very fast. However, it is obvious that Montgomery County took pains to remedy some of the shortcomings of the past. For instance:
Section 1.4
Addresses approved hydraulic modeling software packages. It’s not that the packages are revolutionary. It’s that it requires the use of industry-standard packages. The previous manual did not; it only recommended certain packages. According to one flood plain manager I talked to, this will greatly facilitate the checking of plans. (See Page 10.)
Section 1.5
Specifies “No Adverse Impact” from drainage. The County says, “…one property owner should not be allowed to adversely affect the rights of other members of the community.” This protects the rights of neighboring property owners and also protects the natural systems that provide flood mitigation benefits to the community. It specifically prohibits flooding of downstream neighbors.
Significantly, No Adverse Impact includes impacts other than water surface elevation. They include peak flow, velocity and flow type. (See Page 11.)
Section 2.2.1
Mandates use of certain roughness coefficients for use in different situations. This affects calculations for the speed of runoff. They are critical for determining how fast and high flood peaks will build. In the old manual, calculating the roughness was somewhat subjective. (See pages 16, 48 and 50.)
Section 3.3
Unifies the discussion of erosion controls (both structural and natural) in great detail.
Section 5.3
Requires more storm drain inlets along roads by reducing spacing to 500 feet from 750.
Section 5.4
Requires land plan and street layout changes to improve stormwater conveyance in 100-year events.
Section 6.2
Stipulates that all projects shall mitigate and attenuate the runoff for 5-, 10- and 100-year storm events.
Section 6.3
Requires detention for all proposed developments, regardless of size. It also specifies how the amount will be calculated, and minimum rates (acre feet per acre) for different sizes and types of developments. In addition to other things, it specifies that post-development runoff rates shall not exceed pre-development rates.
Section 7.2
Discusses acceptable floodplain mitigation measures. For instance, “Natural channel clearing to reduce friction losses within the floodplain shall not be allowed as an acceptable floodplain mitigation measure.”
Maintenance
The name and contact information for the entity responsible for maintenance of detention facility, channels, and storm sewers must be listed on construction drawings under the proposed guidelines. “Maintenance shall be the responsibility of the private property owner and not the County,” says the draft manual in various sections.
Still Doesn’t Completely Embrace Harris County Recommendations
From a public protection standpoint, the changes in the new drainage criteria manual may not be revolutionary, but they are a vast improvement according to several hydrologists and a flood forecaster I consulted.
Does it incorporate the minimum drainage standards that Harris County urged surrounding counties to adopt after Hurricane Harvey? Some, but not all of them.
The table below summarizes Harris County’s recommendations and the recommendations reflected in Montgomery County’s draft drainage criteria manual.
Montgomery County already uses Atlas 14 rainfall rates as the basis for all its drainage calculations. That will continue if the new draft drainage criteria are adopted. That’s great.
Even better though is this news. With a few minor exceptions, Montgomery County will require a minimum detention rate of .55 acre-feet per acre. It’s not quite up to Harris County rates, but it’s WAAAAAY better than nothing.
Previously, many developments used hydrographic timing surveys to avoid building any stormwater detention at all. But if adopted, the new drainage criteria will prohibit the use of such surveys. They will require detention for all new developments.
Timing surveys encouraged developers to get their water to bayous as fast as they could, which built flood peaks faster and higher for people downstream.
Fill, Finished-Floor Elevations
Sadly, Montgomery County’s draft drainage criteria would allow fill to be brought into the 500-year flood plain. In extreme events, this could constrict the width of the floodplain and cause a rise in flood levels.
The proposed finished-floor-elevation requirements in MoCo are also less stringent than Harris County. That, however, is the sort of thing more likely to affect Montgomery County residents than those downstream.
I remember owning a new home in the Dallas area back in the early 1980s that was supposed to be 1-foot above the 100-year flood plain. Within three years, it flooded. A new survey by the Army Corps of Engineers found that because of insufficiently mitigated upstream development during those three years, we were actually ten feet below the 100-year floodplain instead of a foot above it.
Montgomery County is also revising its subdivision regulations. They may have more to say on this topic.
Complete Manuals and Summary of Drainage Revisions
To see the old and proposed new drainage criteria manuals, see these links:
Harris County and the Houston area are receiving $863 million from the U.S. Department of Housing and Urban Development (HUD) via the Texas General Land Office (GLO) for disaster relief and flood mitigation. So, on Thursday, April 25, 2024, GLO Commissioner Dr. Dawn Buckingham met with a group of Lake-Houston-Area leaders to discuss the area’s flood mitigation needs.
The meeting, arranged by State Representative Charles Cunningham, also included Director Tina Petersen of the Harris County Flood Control District (HCFCD); Director Thao Costis of Harris County Community Services (CSD); Humble Mayor Norman Funderburk; and Dustin Hodges, Chief of Staff for City of Houston Council Member Fred Flickinger.
(L to R) Dustin Hodges; Tina Petersen; Thao Costis; Dr. Dawn Buckingham; Rep. Charles Cunningham; Norman Funderburk; Alice Rekeweg; Scott Elmer, HCFCD; and Kathleen Jordan.
Projects Vie for Funding
As reported on 4/23, Buckingham was in Houston to discuss Disaster Relief and Mitigation projects totaling $863 million. But there are more deserving projects than money to fund them all. So Buckingham, her team, HCFCD and CSD met with area leaders to discuss needs.
The GLO administers the distribution of HUD funds in Texas. Among Lake Houston Area projects discussed for funding were:
No commitments were made at the meeting, but the mood was positive and everyone left smiling.
Buckingham is still collecting information. She listened attentively, asked probing questions and left with a better understanding of the area’s needs.
Splitting the Woodridge Basin into two phases helps ensure that at least one compartment will get funded and provide enough mitigation to let the Taylor Gully Channel Improvements move forward.
Other Topics
Several other topics came up toward the end of the hour-long meeting. They included sedimentation, dredging, and the need for sand to nourish beaches along the Texas coast. The GLO needs sand to replace eroding beaches…and this area needs to remove sand collecting in streams and Lake Houston.
That raised the tantalizing possibility of collaboration for mutual benefit and solving two problems at once.
More news to follow.
Posted by Bob Rehak on 4/26/24
2432 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2024/04/Buckingham-Meeting.jpg?fit=1100%2C413&ssl=14131100adminadmin2024-04-26 11:38:552024-08-01 16:41:46Area Leaders Meet with GLO Commissioner Buckingham
Harris County Precinct 3 Commissioner Tom Ramsey’s Office will host a meeting about local infrastructure at Kingwood High School tonight. The meeting will include representatives from the City of Houston, San Jacinto River Authority, Congressman Dan Crenshaw’s office, and Harris County Flood Control District.
6:30-8:00 PM
The infrastructure meeting will follow an open-house format. After brief remarks, residents will be free to mingle with representatives from the various organizations at tables set up throughout the room. So you can come and go as you please.
This will give everyone a chance to discuss issues in depth. See details below.
Focus on Infrastructure
Infrastructure covers a lot of territory. Drainage. Roads. Parks. Water. And more.
Recommended Changes in New MoCo Drainage Criteria Manual
In 2019, Montgomery County posted a minor update to a drainage criteria manual first published in 1989. However, in February 2024, the County published a draft of a comprehensive new update to the county’s drainage standards. The 124-page manual is a thorough rewrite that brings the County’s standards up to date and more in line with surrounding areas.
Some Major Revisions
Because the manual is targeted to engineers, it gets very complex very fast. However, it is obvious that Montgomery County took pains to remedy some of the shortcomings of the past. For instance:
Section 1.4
Addresses approved hydraulic modeling software packages. It’s not that the packages are revolutionary. It’s that it requires the use of industry-standard packages. The previous manual did not; it only recommended certain packages. According to one flood plain manager I talked to, this will greatly facilitate the checking of plans. (See Page 10.)
Section 1.5
Specifies “No Adverse Impact” from drainage. The County says, “…one property owner should not be allowed to adversely affect the rights of other members of the community.” This protects the rights of neighboring property owners and also protects the natural systems that provide flood mitigation benefits to the community. It specifically prohibits flooding of downstream neighbors.
Significantly, No Adverse Impact includes impacts other than water surface elevation. They include peak flow, velocity and flow type. (See Page 11.)
Section 2.2.1
Mandates use of certain roughness coefficients for use in different situations. This affects calculations for the speed of runoff. They are critical for determining how fast and high flood peaks will build. In the old manual, calculating the roughness was somewhat subjective. (See pages 16, 48 and 50.)
Section 3.3
Unifies the discussion of erosion controls (both structural and natural) in great detail.
Section 5.3
Requires more storm drain inlets along roads by reducing spacing to 500 feet from 750.
Section 5.4
Requires land plan and street layout changes to improve stormwater conveyance in 100-year events.
Section 6.2
Stipulates that all projects shall mitigate and attenuate the runoff for 5-, 10- and 100-year storm events.
Section 6.3
Requires detention for all proposed developments, regardless of size. It also specifies how the amount will be calculated, and minimum rates (acre feet per acre) for different sizes and types of developments. In addition to other things, it specifies that post-development runoff rates shall not exceed pre-development rates.
Section 7.2
Discusses acceptable floodplain mitigation measures. For instance, “Natural channel clearing to reduce friction losses within the floodplain shall not be allowed as an acceptable floodplain mitigation measure.”
Maintenance
The name and contact information for the entity responsible for maintenance of detention facility, channels, and storm sewers must be listed on construction drawings under the proposed guidelines. “Maintenance shall be the responsibility of the private property owner and not the County,” says the draft manual in various sections.
Still Doesn’t Completely Embrace Harris County Recommendations
From a public protection standpoint, the changes in the new drainage criteria manual may not be revolutionary, but they are a vast improvement according to several hydrologists and a flood forecaster I consulted.
Does it incorporate the minimum drainage standards that Harris County urged surrounding counties to adopt after Hurricane Harvey? Some, but not all of them.
The table below summarizes Harris County’s recommendations and the recommendations reflected in Montgomery County’s draft drainage criteria manual.
Atlas 14, Minimum Detention Rates, Hydrologic Timing
Montgomery County already uses Atlas 14 rainfall rates as the basis for all its drainage calculations. That will continue if the new draft drainage criteria are adopted. That’s great.
Even better though is this news. With a few minor exceptions, Montgomery County will require a minimum detention rate of .55 acre-feet per acre. It’s not quite up to Harris County rates, but it’s WAAAAAY better than nothing.
Previously, many developments used hydrographic timing surveys to avoid building any stormwater detention at all. But if adopted, the new drainage criteria will prohibit the use of such surveys. They will require detention for all new developments.
Timing surveys encouraged developers to get their water to bayous as fast as they could, which built flood peaks faster and higher for people downstream.
Fill, Finished-Floor Elevations
Sadly, Montgomery County’s draft drainage criteria would allow fill to be brought into the 500-year flood plain. In extreme events, this could constrict the width of the floodplain and cause a rise in flood levels.
The proposed finished-floor-elevation requirements in MoCo are also less stringent than Harris County. That, however, is the sort of thing more likely to affect Montgomery County residents than those downstream.
I remember owning a new home in the Dallas area back in the early 1980s that was supposed to be 1-foot above the 100-year flood plain. Within three years, it flooded. A new survey by the Army Corps of Engineers found that because of insufficiently mitigated upstream development during those three years, we were actually ten feet below the 100-year floodplain instead of a foot above it.
Montgomery County is also revising its subdivision regulations. They may have more to say on this topic.
Complete Manuals and Summary of Drainage Revisions
To see the old and proposed new drainage criteria manuals, see these links:
Also see Montgomery County’s Summary of the Revisions.
For easy future reference, you can also find these documents under the Regulations tab in the reports page.
As of this writing, it is not clear when the new manual will go before Commissioners Court for approval.
Posted by Bob Rehak on 4/27/24
2433 Days since Hurricane Harvey
For the more technically inclined, Montgomery County provided this summary of significant revisions.
Area Leaders Meet with GLO Commissioner Buckingham
Harris County and the Houston area are receiving $863 million from the U.S. Department of Housing and Urban Development (HUD) via the Texas General Land Office (GLO) for disaster relief and flood mitigation. So, on Thursday, April 25, 2024, GLO Commissioner Dr. Dawn Buckingham met with a group of Lake-Houston-Area leaders to discuss the area’s flood mitigation needs.
The meeting, arranged by State Representative Charles Cunningham, also included Director Tina Petersen of the Harris County Flood Control District (HCFCD); Director Thao Costis of Harris County Community Services (CSD); Humble Mayor Norman Funderburk; and Dustin Hodges, Chief of Staff for City of Houston Council Member Fred Flickinger.
(L to R) Dustin Hodges; Tina Petersen; Thao Costis; Dr. Dawn Buckingham; Rep. Charles Cunningham; Norman Funderburk; Alice Rekeweg; Scott Elmer, HCFCD; and Kathleen Jordan.
Projects Vie for Funding
As reported on 4/23, Buckingham was in Houston to discuss Disaster Relief and Mitigation projects totaling $863 million. But there are more deserving projects than money to fund them all. So Buckingham, her team, HCFCD and CSD met with area leaders to discuss needs.
The GLO administers the distribution of HUD funds in Texas. Among Lake Houston Area projects discussed for funding were:
No commitments were made at the meeting, but the mood was positive and everyone left smiling.
Buckingham is still collecting information. She listened attentively, asked probing questions and left with a better understanding of the area’s needs.
Splitting the Woodridge Basin into two phases helps ensure that at least one compartment will get funded and provide enough mitigation to let the Taylor Gully Channel Improvements move forward.
Other Topics
Several other topics came up toward the end of the hour-long meeting. They included sedimentation, dredging, and the need for sand to nourish beaches along the Texas coast. The GLO needs sand to replace eroding beaches…and this area needs to remove sand collecting in streams and Lake Houston.
That raised the tantalizing possibility of collaboration for mutual benefit and solving two problems at once.
More news to follow.
Posted by Bob Rehak on 4/26/24
2432 Days since Hurricane Harvey
Ramsey Hosting Infrastructure Meeting at KHS Tonight
Harris County Precinct 3 Commissioner Tom Ramsey’s Office will host a meeting about local infrastructure at Kingwood High School tonight. The meeting will include representatives from the City of Houston, San Jacinto River Authority, Congressman Dan Crenshaw’s office, and Harris County Flood Control District.
6:30-8:00 PM
The infrastructure meeting will follow an open-house format. After brief remarks, residents will be free to mingle with representatives from the various organizations at tables set up throughout the room. So you can come and go as you please.
This will give everyone a chance to discuss issues in depth. See details below.
Focus on Infrastructure
Infrastructure covers a lot of territory. Drainage. Roads. Parks. Water. And more.
Ever wonder:
So many questions! Tonight’s your chance to ask them. And get answers from people who can do something about your concerns.
Be there. Let local leaders know what your infrastructure priorities are.
Posted by Bob Rehak on on 4/25/24
2431 Days since Hurricane Harvey