RAINWATER FLOODING–SOLUTIONS 101

This short course (101) will cover the science of rainwater flooding, how to prevent it, how to fix flooding problems and who must pay for the solution(s).
The Science of Rainwater Flooding
Consider this thought experiment (or you can actually do it). Place a dinner plate in your empty sink with the drain open; the top of the plate will be your yard and the open sink will be Galveston Bay and or the Gulf of Mexico. Next place a cup on top of the plate; this will be your house. Now turn on the water (rain) and let it flow onto the top of the plate. As soon as the water level is high enough to go over the edge of the plate and flow into the Bay or Gulf; no amount of additional rain will raise the water level around your house. Not since the time of “Noah’s Ark” has there been a rain rate that can flood your house if you have adequate drainage.
What about the high tides, storm surges and such? Yes they will flood your house even if you do have good drainage but those rising water events are not caused by rainwater. You just can’t raise the level of the Bay or Gulf any measurable amount with rainwater alone. Oceans and Bay waters will rise because of high tides, storm surges, low barometric pressure, polar ice melting, global warming, tsunamis and another “Noah’s Ark” event but not measurably by rainwater. Rainwater circulates on the Oceans; it evaporates, makes clouds, then rain and then drains right back into the Oceans. Kind of like your hair; mess it up then comb it; think you can measure this making it longer? It may temporarily get longer but not enough to measure.
Preventing Flooding by Drainage
When new communities are designed properly a drainage system is engineered and constructed to economically deal with a defined potential rainwater event (100 year storm etc.). New development additions, age and poor maintenance often cause these systems to deteriorate to a point that they no longer meet the original basic design. Some new ideas like using lower streets and retention ponds to temporarily hold water sometimes help but will not work when a heavy rain event lasts more than a few hours. Remember the reservoir problems in Houston; they filled up and had to be dumped before overflowing.
Guess what, rainwater will always drain away from your house. All that’s required is for the water level in your yard to become higher than the Bay or Gulf. How high depends on how far you are from the Bay or Gulf and how wide the drainage ditch, Bayou or canal is. If the Bay or Gulf is a long way from your house and the drainage ditch, Bayou or canal is not wide enough the water around your house may have to rise; maybe enough to come in your windows or higher. Notice I said wide and not deep. The water in the bottom of a ditch, Bayou or canal is there because it is all lower than the water in the Bay or Gulf. It will not drain now and it will not drain during a storm event even if it were 100 foot deep. That water will not go uphill today nor will it go uphill during a rain event. Making an open canal or Bayou deeper is all about navigation (for deep boats) and has nothing to do with drainage. Sorry about that but to make the Bayou or canal drain more it must be made wider which means destroying the waterfront houses on the banks. There is a case where deeper will work and that is where the drain system is closed like the area under a bridge or the size of a closed pipe. Short term minimum costs fixes can be as simple as cleaning out the underside of bridges. This bridge plugging problem on Dickinson Bayou was evident during “Harvey” and surely contributed to the flooding in the Dickinson area.
Fixing the Problem
1) Widen the drainage ditches, Bayous and canals. Don’t’ waste money making them deeper except as needed for boat traffic.
2) Build new canals.
3) Widen or modify bridges to allow more water flow under. Re-design the entrances so as to minimize the potential of debris plugging the openings; large self-cleaning grates upstream. See Texas City water pump stations.
4) Design new and re-design old systems for future development.
5) Raise minimum base floor elevation requirements for new buildings.
6) Do same as 5 above for major building repairs costing more than 50% of value.
7) Develop long term solutions to minimize or deal with high Bay water levels during major windstorm events (hurricanes, tropical storms etc.); Texas City Levy/pump system, IKE DIKE ???
Who must Pay?
Recently I attended a Galveston County Commissioners Court Workshop on County Flooding caused by “Hurricane Harvey”. I must say that, except for Commissioner Joe Giusti, that sponsored the workshop I did not see much interest from the Court; maybe I’m wrong, hope so. Indeed, with all due respect, the County engineer allowed as to how well the County did in the unincorporated town areas during the “Harvey” event. Remember my thought experiment at the beginning of this story? You can’t flood land next to the ocean. All (Bayview, Caplan, Chrystal Beach, Gilchrist, High Island, Port Bolivar) except Algoa, of the County unincorporated town areas, are located next to Galveston Bay or the Gulf of Mexico. Didn’t hear anything about flooding in Bayou Vista or Tiki Island either did you? You just can’t flood the Bay or Gulf with rain water. This was not an accomplishment of the County; to the contrary all of the flooding in Galveston County occurred in Galveston County. Dickinson’s flooding is not just a Dickinson problem it is a County problem. If Dickinson had the best drainage system in the world and moved all its water to its City limit line then what?
Flooding in Galveston County is a Galveston County problem. All the unincorporated areas of the County and all of the Cities in the County are in the County. The Cities must do their part but the County must take the lead. Further, our County must coordinate with surrounding Counties; in some cases some of their water will have to come thru our County and possibly some of ours thru theirs.
Bottom line about pay is that we all live in and enjoy the County so we all must pay. Or we can do nothing till we suffer again and again expect our bankrupt federal government to spend money it doesn’t have helping us because we failed to help ourselves. Or we can continue to make life here better by paying our share and electing officials that will responsibly lead us.
I hope this short course in Rainwater Flooding Science will be of some use in better understanding what to vote for and who to vote for to get it done.
Now that its been a few months let’s not forget, do noting and get another surprise someday later; Keep it on the front burner, talk, talk, vote etc. till we get something done otherwise we will experience it again and deserve what we get.