Tag Archive for: MaapNext

Flood Bond, MAAPnext Updates Show Projects Slowing

Two new updates provided to Harris County Commissioners on Tuesday 8/2/22 show progress on the 2018-flood-bond and MAAPnext slowing compared to previous estimates.

Flood-Bond Progress

In many ways, the Harris County Flood Control District (HCFCD) Flood-Bond Progress Reports are a model of government transparency. They provide detailed information, even when the news is not all good. The most recent flood-bond update showed that HCFCD:

  • Awarded one more construction contract during July. The count increased from 46 to 47.
  • Awarded 5 new agreements, down from 11 the previous month.
  • Spent only $8 million on bond projects including:
    • $1 million dollars in grant money – $368 million total up from $367 million the previous month.
    • $6 million in bond funds – $551 million total up from $545 the previous month.
    • $1 million in local funds – $141 million total up from $140 million the previous month.
  • Completed 0.2% more of the projects in the bond – 22% up from 21.8%.
  • Finished 21 more buyouts – 802 up from 781.
  • Stayed at .97 on the Key Performance Indicator Scale – slightly behind schedule.
Step by Step, Project by Project

Updates also show the progress of each bond project in the form of detailed GANNT charts. Check pages 4-9 to see projects in your watershed.

For full report in high-resolution PDF format, click here.
Watershed by Watershed

The next two pages show the amounts spent and funded to date in each watershed. These maps give readers a good idea of where the money goes. Draw your own conclusions and remember the map below when certain politicians tell you some watersheds don’t get anything.

Screen Capture from Page 10 of Full Report
Active Construction

The last two pages describe updates on active maintenance and construction projects with spending on each. They show that – five years after Harvey – the Lake Houston Area still has only two active capital projects in construction. Both are excavation and removal contracts for $1000 each.

Pace of Projects Slowing

From looking at these reports month after month, it feels as though the pace of activity has slowed. We’re 40% of the way through the 10-year flood bond in terms of time, but only 22% complete. The gap is getting wider. Worse…

At the rate of $8 million per month, it would take 500 months to spend the next $4 billion in the bond.

That’s more than 40 years, not the 10 originally planned. We need explanation. But HCFCD executives were not immediately available to provide it due to travel schedules. I will follow up.

MAAPnext Progress

MAAPnext is the county’s effort to update flood-risk maps in the wake of Harvey. There’s not much new to report.

The timeline has slipped three months. In earlier updates, HCFCD indicated new maps would be released in spring/summer this year. Now, the target has slipped to summer/fall. A large portion of the update consisted of trying to explain why. In a sentence, “We’re waiting on FEMA.”

So I tried contacting FEMA. But FEMA could not provide a more precise estimate.

Harris County followed standard practice by submitting its findings to FEMA prior to public release. FEMA is currently reviewing all data and models. It is also producing preliminary Flood Insurance Rate Maps (FIRMS) based on those models. The data will help determine flood insurance premiums as FEMA moves to an actuarial-based system called Risk Rating 2.0.

Next Steps

When FEMA is ready, it will first brief community officials and floodplain administrators, and give them access to preliminary data. Shortly thereafter, FEMA and HCFCD will hold a series of open houses to brief the public. Public comment periods and appeals follow.

So, at best, the new maps will be released in 2024, seven years after Harvey. That’s fairly consistent with the length of time it took to finalize new flood maps after Tropical Storm Allison in 2001. Those maps became official on 6/17/2007.

But this process is far more complex because of Risk Rating 2.0. It includes individual flood-risk assessments for millions of homes. And that risk assessment will now also include street flooding, not just coastal and riverine flooding.

Posted by Bob Rehak on 8/5/2022

1802 Days since Hurricane Harvey

Progress Reports on New Floodplain Maps and Flood Bond

On Tuesday, 5/24/22, the Flood Control District transmitted updates on two projects (MAAPNext and the 2018 Flood Bond) to Harris County Commissioners. New Flood Insurance Rate Maps (floodplain maps) should be released within the next six months. In related news, the entire northeastern part of Harris County is still getting less than one thousandth of one percent of all active construction spending on bond projects.

For more detail read on.

MAAPNext Data Still Being Validated

MAAPNext stands for the next-level Modeling, Assessment and Awareness Project. In the wake of back-to-back-to-back 500-year floods in 2015, 2016, and 2017, it became clear that the floodplain maps which guided development in Harris County woefully underestimated the real flood risk in the region.

In response, the Harris County Flood Control District, NOAA and FEMA launched the MAAPNext project. It began by acquiring new, more accurate topographic (elevation) data for every watershed in the county and surrounding areas. They used LiDAR data with 9 times more resolution than the maps developed after Tropical Storm Allison in 2001.

Harris County Flood Control District then modeled updated rainfall probability statistics (Atlas-14 data) from NOAA against the terrain data.

FEMA is now reviewing the results and validating data. Within the next few months, FEMA will release new floodplain maps. This graphic shows the timetable and stages.

HCFCD has completed its part of the work and estimates FEMA has completed 20% of its at this point.

Preliminary Maps Coming in Few Months

FEMA should release PRELIMINARY Flood Insurance Rate Maps this summer or fall. After the release, expect a series of public meetings. During those meetings, partners will explain the results and the public will get a chance to ask questions and/or protest the results.

For instance, some people may have raised the elevation of their buildings since development of the new maps. Maps that do not reflect such improvements could raise flood insurance rates.

Other people will no doubt question the validity of the data, because expanded floodplains may adversely affect their property values. People who have received no flood mitigation help so far from the bond will suffer more in this regard than those who have.

Following the public comment and review periods, FEMA will revise floodplain maps as necessary and then release final versions. It could take another 3+ years before we see final maps.

In the meantime, you should assume that the old floodways will expand into the 100-year floodplain and the 100-year floodplain will expand into the 500-year floodplain.

So it’s best to get flood insurance now if you don’t have it. Remember, if you are in the 100-year floodplain, your chance of flooding during the life of a 30-year mortgage is about 1 in 4. And a lot of people don’t yet realize they live in a floodplain!

To see the full MAAPNext update, click here.

Flood Bond Now 21% Complete

HCFCD also released its May update on the progress of 2018 flood-bond projects last week. Through the end of April 2022, the District has completed 21.3% of the bond program.

The District has spent $1.025 billion out of about $5 billion in bond and partner funds. Spending breaks down like this:

  • $533 million in Bond Funds
  • $356 million in Grants
  • $136 in other Local Funds.
Where HCFCD spent a billion dollars.

The update acknowledges the $2.2 million grant from the Texas Water Development Board for the second phase of the Lauder Stormwater Detention Basin on Greens Bayou. Supposedly, Phase 2 has already started construction, though I could see little more than road work last week.

Other projects starting construction last month included:

  • Bayside Terrace Subdivision Drainage Improvements
  • Barker Watershed Repairs

Active construction of capital improvement projects totaled $236 million in May. Out of that, the entire northeastern part of the county still had only $2,000. That’s right. $2 thousand out of $236 million. That’s 0.0008%.

To see the entire flood bond update, click here.

Posted by Bob Rehak on 5/29/2022

1734 Days since Hurricane Harvey

Of Active HCFCD Bond Construction Spending Totaling $226 Million, Lake Houston Area Has $2 Thousand

Harris County Flood Control District (HCFCD) delivered its March 2022 Flood Bond Spending Update yesterday to Commissioners Court. It shows $226,476,745 dollars worth of active capital construction projects underway throughout the county. But only two of those valued at a grand total of $2,000 are in the Lake Houston Area.

That’s less than one-tenth of one percent, despite the fact that the Lake Houston Area was one of the most heavily damaged in the county during Harvey.

Maintenance Costs Harder to Determine

The update also includes active maintenance projects. However, those are grouped in ways that make it difficult to determine the exact cost of each. The Lake Houston Area had 3 out of 36 of those. At least one of the three is now complete. It consisted of cleaning a block-long stretch of the drainage ditch that parallels Stonehollow Drive in Kingwood. Judging by the group costs, none of the three qualifies as major.

The update does not disclose the value of past projects. Nor does it break out the value of studies, right-of-way acquisition, or future improvements.

For the full update, click here. I compiled the numbers above from the last two pages in the PDF. To see the location of projects, check the HCFCD’s Flood Education Mapping Tool. It shows the number of every ditch and stream in Harris County.

Other Insights

The report yields many insights.

  • 19.7% of the bond work has been completed as of the end of March. That’s up from 19.4% at the end of February. That percentage should increase faster as HCFCD completes more preliminary studies and moves into the expensive phases of projects, such as right-of-way acquisition and construction.
  • Of 1175 buyouts identified, 457 have completed – 39%.
  • Biggest winners to date in the flood-bond, mitigation-funding sweepstakes have been:
    • Brays Bayou – $173.1 million
    • Cypress Creek – $87.4 million
    • Greens Bayou – $82.7 million
    • Addicks Reservoir – $75.4 million
    • Little Cypress Creek – $53.7 million
    • White Oak Bayou – $53.2 million
    • Clear Creek – $38 million
    • Halls Bayou – $35.4 million
    • Hunting Bayou – $34.1 million
    • Willow Creek – $33.5 million
  • The San Jacinto River watershed has received $20.7 million despite being the largest in the county.
  • HCFCD completed two projects during the month and began construction on one other.
  • Eight other projects changed stages, i.e., from feasibility study to preliminary engineering.

“Partner Funds” To Date Virtually Equal “Bond Funds”

Virtually half of flood bond spending through the end of March 2022 came from partner funds. Local funds plus grants totaled $483 million. Money spent out of the bond itself has totaled $492 million. So, 49.5% of spending to date came from partner funds. It has gone largely to watersheds supposedly disadvantaged by partnership requirements. A popular political narrative claims low-to-moderate income watersheds get no partner funding and more affluent watersheds get it all. But that simply isn’t true.

The narrative is being used to accelerate the start of projects in LMI neighborhoods by decoupling grant approval and project initiation. However, as these numbers show, turning our backs on partnership funds could potentially double the cost of flood mitigation.

49.5% of mitigation dollars to date have come from partners. 50.5% came from the bond itself.

Glaring $750 Million Omission

Although the March update contained a discussion of several partnership grants, it failed to mention $750 million allocated to Harris County by HUD and the GLO for flood mitigation on March 18. The March update did, however, discuss several smaller grants, earmarks and partner funds. Those took up two and a half pages.

The $750 million, together with the flood resilience trust approved last year, would fully fund the flood bond. That means that no watershed should have to wait on partner funding for construction projects to begin once engineering is completed.

Only one step remains before Harris County can start using the money – approval of a “method of distribution.” That’s a final plan for how and where the money will be used.

Posted by Bob Rehak on May 11, 2022

1716 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.

MAAPnext Offers Powerful Historical Flood Loss Visualization Tools

By accident, I stumbled across some powerful historical flood loss visualization tools on Harris County Flood Control’s MAAPnext site today. They can help you understand the capricious nature of storms as well as political claims about which neighborhoods flood the most.

About MAAPnext

In 2019, using two FEMA grants and Flood Bond money, Harris County Flood Control District launched its MAAPnext project. MAAP stands for Modeling, Assessment and Awareness. The goal: to use new methodologies and technologies to improve understanding of flood risks throughout Harris County. The project goes far beyond updating Flood Insurance Rate Maps in the wake of recent storms. It also includes:

  • Interactive historical flood loss visualization tools
  • Water surface elevation change grids (maps showing difference between effective and revised floodplains)
  • Flood depth grids (for various flood frequencies including 10%, 4%, 2%, 1% and 0.2% annual chance events)
  • Urban flood maps (street flooding caused by rainfall exceeding storm sewer capacity)
  • Percent annual chance grids (giving you your exact probability of being flooded within a mapped floodplain)
  • 30-Year chance grids (showing your home’s exact chance of flooding within the life of a 30-year mortgage)
  • Water surface elevation grids (showing the water surface elevation in various flood frequencies)

Not all of these maps have been released yet. For instance, MAAPnext/FEMA will release new preliminary flood insurance rate maps for public comment this fall. However, I did find three fascinating interactive maps showing the history of flood losses in Harris County.

Historical Flood Loss Tools

Cumulative Losses since 1978

The first map provides a visual representation of where all flooding claims have occurred throughout the county since 1978. A property’s flood risk can be a influenced by many factors but it’s important to remember that it can flood anywhere in Harris County. The darkest areas have the most cumulative flood losses. The lightest areas have the least.

Total flood losses in various census tracts within Harris County since 1978.

To understand exactly WHERE and WHEN these flood losses happened, you need to go to the next two series of maps.

Historical Inundation Map

The Historical Inundation Map shows the extent of flooding in five different major storms since 2015. These include only streams with gages, not all Harris County channels. Zoom and scroll into an area of interest and then select the storm of interest from the layer menu.

Extent of flooding along the West and East Forks in the Memorial Day 2016 flood.

You can toggle layers rapidly to see how floods compared to each other.

Flood-Loss History by Event

The map above shows the spread of flood waters in various events. However, to see the relative damage in census tracts, you need to go to the map called “Flood Loss History by Event.” Again, you’ll need to toggle layers to select the event of interest. The darker the colors, the more damage.

Tax Day 2016 Storm Damage
Selecting the Tax Day 2016 layer shows that most damage from that storm occurred in NW Harris County.
Hurricane Harvey 2017 Damage
Selecting the Harvey layer shows that that storm affected the entire county with some watersheds experiencing more losses than others.
Imelda 2019 Damage
Distribution of damage in Harris County from Tropical Storm Imelda

For More Interactive Exploration…

The four maps above only scratch the surface of what you can find on the MAAPnext site. To explore the distribution of damage in various storms, visit the page called Understanding Your Flood Risk.

Media accounts of major storms might lead you to believe that major storms affect all parts of the county equally. But they don’t. Who floods depends on upstream rainfall totals, dam releases, proximity to floodplains, development regulations, elevation above the flood plain and more.

The most interesting aspect of MAAPnext is that it will eventually incorporate all of these factors and give you an individual risk rating for your property or one that you are considering buying.

If knowledge is power, this is power cubed, because it let’s you look at flood risk in multiple dimensions.

Be Patient

I can’t wait until the project is fully finished. Check back often and click around this site as new features seem to be bolted on periodically. The bolted-on comment relates to my only complaint. All information (and there’s a lot of it) is grouped under five pages in ways that are rarely intuitive and often invisible from the highest levels. For instance, to get to the historical flood loss maps, you have to:

  • Click on the home page
  • Click on a link embedded in one of the visuals called “Flooding is Our #1 Disaster.”
  • It will take you to a page called (strangely enough) “Understand Your Flood Risk.”
  • Scroll down past 7 other topics to the bottom of page to find the interactive maps.

Presumably, helping people understand their flood risk is the most important objective of this site, but the page by that name appears nowhere in navigation. That said, have fun exploring. You’ll find many other hidden gems on this site.

And remember that all flood insurance policies renewing on or after April 1, 2022, will be subject to FEMA’s new Risk Rating 2.0 methodology.

Posted by Bob Rehak on 3/12/2022

1656 Days since Hurricane Harvey

Where Flood-Bond Spending Is Going, When New Flood Maps Will Be Released

On the Harris County Commissioner’s Court agenda for today are two Harris County Flood Control District (HCFCD) “transmittals.” One will update commissioners on flood-bond spending to date. The other will update commissioners on the progress of new flood maps (the MAAPnext program). They are items 269 and 270 on today’s agenda.

Transmittals are reports by departments. Commissioners don’t usually discuss them unless one of the commissioners wishes to make comments for some reason. So, I’m calling them to your attention here.

Flood-Mitigation Spending Through Third Quarter Reaches $865 Million

About half of the $865 million spent on flood mitigation since voters passed the bond in 2018 has come from bond funds. The rest has come from grants and local partnerships. See pie chart below on left.

The left pie chart underscores the importance of partnership funding.

The map below shows where flood-bond spending has occurred.

Flood-mitigation spending by watershed since approval of flood-bond in 2018.

The winner in the $weep$take$: HCFCD spent almost $154 million on Brays Bayou.

Other leading watersheds (rounded to nearest million) in flood-bond spending included:

  • $81 million in Addicks Reservoir
  • $76 million on Greens Bayou
  • $76 million on Cypress Creek
  • $50 million on Little Cypress Creek
  • $46 million on White Oak Bayou
  • $32 million on Clear Creek

With a few exceptions, this spending reflects the influence of the Harris County Flood-Bond Equity Prioritization Framework implemented in 2019. That framework gives highest priority to low- to middle-income watersheds with a high social-vulnerability index. Thus, tiny Halls Bayou has received more assistance than the largest watershed in the county – the San Jacinto River. And Brays Bayou has received almost 11 times more assistance than Buffalo Bayou.

Two notable exceptions are:

  • Vince Bayou which is almost totally inside the City of Pasadena and is therefore primarily Pasadena’s responsibility.
  • Little Cypress Creek which is part of HCFCD’s experimental Frontier Program. The Frontier Program aims to prevent future flooding by buying up land on the cheap before it’s developed. HCFCD then sells detention basin capacity to developers to help make back its investment.

Other Insights Gained from Report

  • Most projects are ahead of schedule and on budget. Good news!
  • More than half of buyouts have been completed and enough funding apparently remains to complete the rest.
  • Progress continues on the $124 million FEDERAL Flood Damage Reduction project on White Oak Bayou, where six stormwater detention basins will hold almost a billion gallons of stormwater. That’s equivalent to about a foot of stormwater falling over almost 5 square miles.
  • No actual projects in the Kingwood Area have begun construction yet. However, the Excavation and Removal Project on Woodridge Village could soon begin.

Additional maps in the full report show:

  • Dollars funded to date by watershed (Note, for instance, another $47 million in funding already committed to Brays).
  • Active Maintenance projects
  • Active Capital projects

Also, a massive GANNT chart shows the stages of every project in every watershed and county-wide projects.

Check out the full report here.

Controversy over Previous Version of Report

An earlier version of this report generated some controversy. People in some watersheds didn’t believe the reported expenditures. Members of the Northeast Action Collective questioned whether any projects had started in their watersheds. They demanded immediate cancellation of projects in Kingwood and transfer of Kingwood’s funds, so that projects in Halls and Greens Bayou could start immediately.

That’s, in part, why I wrote “How to Find and Verify Flood-Related Information: Part I.” Flood-mitigation projects are hard to spot from the ground. Construction almost always happens out of sight behind tall fences and dense tree lines. After construction, the projects are often disguised as parks. For those who doubt, I recommend confirming the existence of projects from the air.

I haven’t confirmed every project in the county, but I have spot-checked many. And I have yet to find discrepancies between what HCFCD reports and what I can see from the air.

C-25, a Halls Bayou Detention pond now under construction by HCFCD
C-25, a Halls Bayou Detention pond now under construction by HCFCD. The bayou runs through the trees in the foreground.
flood detention basin
New basin at Hopper and US59 on a tributary of Halls Bayou.
Lauder Detention Basin on Greens Bayou as of 10/12/2021
Lauder Detention Basin on Greens Bayou as of 10/12/2021. Phase One of a two-phase project is nearly complete.
Cutten Road detention basin on Greens Bayou continues its relentless expansion.
Phase 2 Aldine Westfield Basin
Phase 1 of the Greens Bayou Aldine-Westfield Basin on left is complete. Phase 2 on right is now beginning.

For more information that includes watershed spending data before the flood-bond, check out the funding page.

MAAPnext Effort About to Be Turned Over to FEMA

Harris County Flood Control (HCFCD) estimates it has completed 86% of its part of the flood-map updates. HCFCD will deliver drafts of the new maps to FEMA in January for review and kick off a campaign of public meetings at the same time. The public will see draft maps in February. A public comment period of 90 days will follow. And FEMA hopes to release preliminary flood insurance insurance rate maps by mid-year next year.

I have had a peek at the new maps and reports. And I must say, the effort should result in a dramatic leap forward in flood-risk understanding. Individualized reports will inform homeowners of their flood risks from a variety of different sources, including street flooding. The prototype of the website is very user friendly.

After receiving preliminary maps from HCFCD, it typically takes FEMA another 18-24 months to release final, official flood maps. That gives affected property owners time to comment and appeal. The process looks like this.

MAAPnext milestones as of the end of 2021.

Posted by Bob Rehak on 11/30/2021

1554 Days since Hurricane Harvey

Progress Report on New Flood Maps and Flood-Insurance-Risk Ratings

On June 29, 2021, Harris County Flood Control District (HCFCD) gave Commissioners an update on the progress of new flood maps and flood-insurance-risk ratings. The flood-map changes could become effective as early as late 2023. FEMA’s new Risk Rating 2.0 system for flood-insurance pricing will be phased in during the next few years. See details below.

MAAPnext About Half Complete

MAAPnext is Harris County’s Modeling, Assessment and Awareness Project. The purpose: to develop the next generation of flood maps and tools. It will provide a better assessment of flood risks for individual properties, and make the nature of those risks easier for property owners to understand.

One of the significant changes: the new maps will capture different types of flooding, such as street flooding. This is currently the biggest missing piece of the flood-risk rating picture, according to the MAAPnext project team.

The new maps will also come with individual property reports that estimate flood depth, water-surface elevations, annual-chance of flooding grids, and 30-year chance of flooding grids. That last will estimate your chance of flooding at least once during a 30-year mortgage. The flood map grids will also be more detailed. They will provide estimates down to the 3 ft X 3 ft level.

FEMA and Harris County expect to have:

  • Draft flood-risk maps and associated data available for public review by the end of this year.
  • Preliminary Flood Insurance Rate Maps (FIRMs) for release by next summer.
  • Public meetings to review and explain the FIRMs to officials and residents during the second half of next year.

The earliest likely date that the new rate maps could become effective: late 2023.

Changes to flood-insurance premiums as a result of map changes could only happen after the new maps become effective.

Understanding FEMA’s Risk Rating 2.0

Risk Rating 2.0 is a massive FEMA effort to put the National Flood Insurance Program (NFIP) on a sound actuarial footing.

FEMA is updating the National Flood Insurance Program‘s (NFIP) risk rating methodology through the implementation of a new pricing methodology called Risk Rating 2.0. The methodology leverages industry best practices and cutting-edge technology to enable FEMA to deliver rates that are actuarily sound, equitable, easier to understand and better reflect a property’s flood risk.

More Risk Factors Considered

Elevations, flood-hazard zones, and rating tables will no longer be the only metrics used in calculating the flood-insurance premium for a property. For example, premiums will be distributed across all policyholders based on home values and a property’s unique flood risk. FEMA will also consider flood frequency, multiple flood types—river overflow, storm surge, coastal erosion and heavy rainfall—and distance to a water source along with property characteristics such as elevation and the cost to rebuild.

More Equitable Rates

Currently, many policyholders with lower-value homes are paying more than they should and policyholders with higher-value homes are paying less than they should.

That said, FEMA expects 87% of single-family homes to see a flood-insurance-premium increase of about $120 per year. Another 4% could see an increase of about $121 to $360 per year. Finally, 9% could see a decrease of up to $1,200 per year.

Source: FEMA Fact Sheet – County-Level Premium Change Analysis reproduced in HCFCD document

Phased Implementation

Beginning October 1 this year:

  • New policy holders will be subject to the new rates.
  • Current policy holders eligible for renewal can take advantage of premium decreases.

Starting in April 2022:

  • Existing policy holders who expect an increase with the new method could renew under Risk Rating 2.0, but will have an option to keep their current policies if cheaper for up to two years.
  • All remaining policies renewing on or after April 1, 2022, will be subject to the new rating methodology.  

Contact your flood insurance agent to clarify all timing, rate and discount questions.

How Does MAAPnext Factor into Risk Rating 2.0?

Harris County Flood Control District in partnership with FEMA lead the MAAPnext effort to revise flood insurance rate maps. FEMA alone leads the Risk Rating 2.0 effort to calculate new flood insurance rates. The maps will help calculate new premiums.

For more information, visit the MAAPnext website or the Risk Rating 2.0 section of FEMA’s.

Posted by Bob Rehak on July 4, 2021 based on information from HCFCD and FEMA

1405 Days since Hurricane Harvey

Interim Guidelines for Atlas-14 Implementation Until New Flood Maps Released

While reviewing the MAAPnext website today, I came across this 1-page PDF that outlines major changes to Harris County’s Policy Criteria & Procedure Manual (PCPM). It describes changes – based on new Atlas-14 Rainfall Statistics – that engineers and developers must follow when designing and constructing flood-control features as part of any development within Harris County.

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’

Harris County works with surrounding counties and municipalities to upgrade and harmonize their floodplain regs. However, the effort has not yet yielded much fruit.

Surrounding counties, such as Liberty and Montgomery, have not yet mirrored these restrictions. In fact, those counties still use their comparative lack of regulation as a competitive tool to attract new development. That, of course, makes it doubly difficult for residents of Harris County. They must not only contend with their own runoff, they must contend with their neighbors’.

Posted by Bob Rehak on 11/30/2020

1189 Days since Hurricane Harvey

New Flood-Map Timetable and How It Affects New Development

Because of low interest rates, new developments seem to pop up weekly around the Lake Houston Area. The question often arises, “How will the development of new flood maps affect the development of new subdivisions?” Most people by now have heard that City building code revisions now require elevation at least two feet above the .02-percent-annual-chance flood (formerly known as 500-year flood). But does that mean two feet above the old floodplain or the new? Due to a little-known provision in the City’s floodplain regulations, it means the new floodplain even though the new floodplain maps are not official yet.

Developments in various stages in the northeast Houston Area and the City’s ETJ (extra territorial jurisdiction). From City of Houston Plat Tracker Plus.

Timetable for Updating Flood Maps

Here’s what you need to know if you’re concerned that someone may be building future buyouts next to your neighborhood. First the timetable for new flood maps.

Remaining timetable for new Harris County Flood Maps

Even though FEMA won’t release the new flood maps officially for approximately another five years, developers should still be building to the higher standards associated with newly acquired data (in other words, the data on which the new maps are being built). See below.

Floodplain Regs Authorize City Engineer to Use Data Behind New Flood Maps

Section 19-4 of the City’s Floodplain regulations address Use of other flood hazard data to supplement the effective Flood Insurance Rate Map (FIRM). It states, “New elevation and flooding studies are undertaken by or under the auspices of FEMA and local political subdivisions, such as the Harris County Flood Control District. Upon determination that the data generated by such a study appears to be reliable and based upon sound engineering and surveying practices and further that the study’s data indicate that the effective FIRMs are FIRM is materially inaccurate, the city engineer may cause the study data to be administered for purposes of this chapter as though it were a part of the effective FIRM. Any such determination shall be issued in writing and a copy shall be placed on file in the office of the city secretary. The city engineer is authorized to utilize updated information from FIS and floodplain models in administering this chapter.”

Basically, that means even though the new maps have not yet been adopted, the City Engineer can require developers’ plans to reflect the new underlying data as though it were part of the current map. In this case, the new underlying data is already in hand.

MaapNext Website Describes New Data Improvements

Current floodplain maps will change greatly according to Harris County Flood Control. The district has already started releasing information on a new website called MaapNext (Modeling, Assessment and Awareness Project).

Components of the MaapNext program. A $3.5 million FEMA grant made MaapNext possible.

According to the MaapNext site, we now have updated data based on:

  • County-wide impervious data developed from 2018 aerial imagery
  • Completed flood risk reduction projects
  • NOAA’s recently-released Atlas 14
  • Updated terrain data

We also have new and better ways to model that data since the last survey after TS Allison:

  • 2-Dimensional Hydraulic Modeling
  • New hydrology method that better accounts for a watershed’s conveyance capacity
  • Rain-on-Grid analysis that identifies previously unmapped urban flood risk.

And, we are beginning to develop better maps:

  • Modeling results in GIS (Geographic Information Systems)
  • New flood-risk data sets describe results in a variety of useful ways

Reportedly, the City is already requiring developers to act on the new “best available data” instead of waiting five years for the next maps.

Chapter 19 of the City Ordinances deals with dozens of other requirements for building in floodplains. But more on those in future posts.

Posted by Bob Rehak on 8/29/2020

1096 Days (Three Years) since Hurricane Harvey

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