During our meeting people began to realize that the increased density called for in Chapter 42 would worsen flooding. They asked what they might do. Below is my quickly written reply. The hearing for Chapter 42 is April 10th, 2013, so we need to educate people quickly about what we can do and what we need to ask for.
Thanks for getting involved. There are several things that you can do:
1) call and email politicians to let them know your concerns. That includes your council member and all 5 at large members
2) talk with friends and neighbors to educate them about Chapter 42 and your concerns about it.
3) alert your civic association and super neighborhood about your concerns and your suggestions for a solution.
4) make plans to attend the April 10th hearing and sign up to speak.
5) contact your County Commissioner to ask for more detention in our area and ask the County to be more restrictive when they know the City is doing things that will cause more flooding. While we may be in the incorporated area, what happens in the City affects the County and vice-versa.
Talking points are:
1) Suburban roadways were built assuming suburban densities so storm sewers are inadequate above 45% impervious cover. Chapter 42 allows up to 96% impervious cover for residential building so we should increase the City standard for runoff coefficient to 100% for urban areas and don’t assume that parks have a runoff coefficient of 18%, particularly for urban parks that are well packed from foot and bike traffic.
2) Too many variances have been allowed on new builds so there is too much concrete and not enough detention; i.e., do not grant more unwarranted variances.
3) Enforce existing ordinances. Grandfathering wouldn’t as big be a problem if the ordinances had been enforced to begin with. Once detention for a property is incorrectly calculated, under current rules it is grandfathered forever.
4) End grandfathering completely. As you saw from the slides, the actual 100-year floodplains are dramatically bigger than FEMA indicates when runoff water is considered. We live in a very flat subtropical area near a large body of water where heavy rain is always possible. If runoff water cannot get to the drainage system, then flooding occurs. The maps showed that in the majority of the area modelled, drainage is inadequate and structural flooding is likely to occur in a major rain event.
5) The Manning number used by the City (0.04) for open ditches assumes a nearly worse case for the ditch and optimal case for enclosed pipe, so it allows a large ditch to be replaced by a much smaller pipe, effectively reducing drainage capacity. This was used in our area to dramatically reduce the capacity of the Bunker Hill Bridge, causing water to back up pipes and flood roads and homes. It’s at least partially responsible for the severe flooding along I-10 feeder roads where the large ditches along the MKT rail line were replaced with much lower capacity underground drainage. Choosing a smaller Manning number would require a larger pipe size, so for a City beset with drainage issues, assuming the same Manning number as concrete, for instance, would automatically add drainage capacity when a roadway is rebuilt with underground drainage.
6) Use low impact design practices. This might be as simple as using permeable concrete for parking lots. Other ideas are using cisterns (a water “retention” system) to capture rainwater for watering, rooftop gardens that reduce runoff, plant trees for shade and to absorb water.
We have years of bad building practices to overcome with diminishing opportunities to buy land to install the necessary large detention facilities. After 3 hours of rain, land becomes water saturated and we have 100% runoff, therefore, even without grandfathering, we only mitigate for 50% of the covered ground used for development. We should incentivize detention by providing breaks from the Rebuild Houston fee to those who add extra detention on their properties.
In “Drainage Attainment Districts” (DAD’s), my term, we can use a percentage of tax money from local homeowners and businesses to pay developers to store more water than is required on their property. DAD’s would be set up much like a TIRZ, but would specifically require that area detention be installed; i.e, no grandfathering. After the area’s detention needs are met and the cost of the facilities paid for, the tax would end, however exemptions from Rebuild Houston fees might extend for the developers as long as the detention remains in place.
I’m sure that there are many other ideas that you will uncover when your start talking to people.