Flooding

[txcat84]

The topic of flooding is en vogue for obvious reasons, particularly in regards to the theoretical new HEB going up IF dry law is relaxed and IF HEB decides to build on the location at 23rd and Shepherd. 

 

My question is if this development proceeds:

 

- What would be the impact radius of increased flooding that may occur? 1 block? 5 blocks? Just the immediate neighbors?

 

- What would the most responsible way to handle run-off be?  Retention (wouldn't mind an explanation of how this works)? Are there other alternatives?

 

- Would area residents have recourse? Is there a way to mandate a certain course of action?

 

I have no experience with this. I'm not a NIMBY. I don't have an opinion one way or another (don't want to see neighborhoods flood, lose character etc. OR for developers to run off because of  too many stipulations) I'm just genuinely curious and would love to see this board a little more active!

 

Ready, go.

[HNathoo]

It theoretically won't have any impact. Any increase in impervious cover should be offset by added retention/detention capacity. 

[innerloop]

7 hours ago, HNathoo said:

Any increase in impervious cover should be offset by added retention/detention capacity. 

 

I don't see how there can be any increase in impervious cover.  Isn't the entire lot already paved over?

[s3mh]

People in Spring Branch blame the new Bunker Hill HEB for increased flooding in the area.  Their argument is that HEB elevated the property a few feet when they built the new store which caused storm water to drain off faster and also blocked the sheet flow of water in big storms.  They claim that areas that never flooded in relatively minor storms started flooding after the store was completed and the Memorial day flood was especially devastating because of the new development in the area.  The City through the local TIRZ had promised to build a bunch of detention/retention ponds to mitigate all the new development along the I-10 corridor, but did not follow through.  A group of residents filed a lawsuit against the TIRZ to compel them to make the promised flood infrastructure improvements.

 

It is hard to say whether these arguments mean much when you get a rain event of 15+ inches.  I am not sure even the most aggressive storm mitigation requirements would stand up to such a massive amount of water.  It may be more of an argument about limiting the extent of the flooding, which is a valid point, rather than eliminating flooding.  We just get too much rain too fast in Houston.

 

I do not see redevelopment of the Fiesta having much of a direct impact on the neighboring properties.  The north/south streets in the Heights do a very good job as the drainage system of last resort.  In each of the last big rain events, I watched the street in front of my house turn into a pretty fast moving river.  Out in Spring Branch, a lot of the streets in the neighborhoods are east/west.  Once the storm water system fills up, the east/west streets do not carry water away and just fill up and flood houses.  

 

But on an indirect level, the City's policy of allowing redevelopment of large tracts without providing any storm water retention/detention is a bad policy that needs to change.  The logic behind the policy is that the existing storm water drainage system is sufficient to meet the needs of all the properties built up to the date the City began requiring detention when increasing impervious cover (some time in the 1970s, I believe).  So, if you redevelop a property that has existing impervious cover, you are not responsible for doing any detention/retention.  But the problem with the policy is that the existing drainage system is not sufficient, especially in light of the recent increase in the frequency of 100 year flooding events and the pressure upstream development has placed on downstream drainage infrastructure.  I understand that developers claim that no one will ever build on anything larger than an acre in the City if they are required to put in drainage.  I think that is a bit of BS.  But even if that is true, why not do a development agreement using one of the tools in the City's tool box (i.e. 380 agreements, etc.) to allow the developer to recover the cost in tax abatements/refunds from the property and sales tax generated by the property?  The Walmart developers got $200k to put in a crushed granite trail on the esplanade that is almost completely grown over.  Why not use that kind of funding scheme to actually do something to benefit the community and use it to require developers to put in onsite detention?

 

 

 

[bedmondson]

As previously stated, redevelopment raising their properties and not being required to do detention because of no net change in existing impervious cover is the problem.  When redevelopment happens in the 100 year floodplain this isn't a problem because there is a requirement that mandates no net fill to be brought onsite. 

Have you noticed that the Fiesta property holds water or has a ponding issue after a big storm? If there isn't an existing onsite drainage issue redevelopment there probably wont be any impact on the neighbors IF it the property is raised. Its when an old property that use to hold water during event because it was built to low is raised that issues like this can come up.

 

There is no recourse I am aware of as long as they meet current building criteria. In the future City council could pass a new ordinance updating regulations on redevelopment.

 

Also are we sure Walmart didn't provide onsite detention? I believe they would have been required to and they typically install their detention under their parking lots.

[Angostura]

Dumb Swamplot comments to the contrary, this property is neither in the floodplain nor the floodway, and does not detain water during storm events. Raising this property by 100 feet would not affect flooding on adjacent tracts, since it's already graded above street level, and 100% of storm water already runs off immediately.

 

Whether brownfield developmentslike this that don't increase impervious cover should add detention anyway in order to compensate for changes upstream (and out of the control of CoH) is another question entirely, the answer to which is not as simple as, "Yes, of course they should."