To flood or not to flood – that is the question!
I asked Jeff Lindner, meteorologist for HCFCD, about the Halloween storms (as seen below). I also asked his opinion about how much rain along Cypress Creek in a ~24 hour period will flood the creek. His response:
“The Halloween rainfall event came toward the end of several weeks of wet weather over the area that have maintained a wet to saturated ground state. The event on Halloween produced a basin average rainfall of 2-3 inches across the Cypress Creek watershed and 3-4 inches across the headwaters along the Waller/Harris County line. Additionally much of this rainfall fell in a fairly short period of time of 4-6 hours in the late afternoon and early evening hours of Halloween. The widespread coverage of rainfall on top of already soggy ground led to more run-off than usual for this particular event. One thing to keep in mind is that each rainfall event is different: ground state, rainfall patterns, amounts, ect. And each of these variables will produce differing rises on the watershed. One thing to remember is there is a lot of capacity in the upper part of the channel compared to the lower portion of the channel…so it takes much more rainfall to fill that upper portion capacity than the lower portion.
The 24-hr storm totals that I look for with a normal ground state would be 5-7 inches to get Cypress Creek to bankfull or slightly above across much of the basin (or at least above a certain location).”
There you have it – Cy Creek will probably go out of its banks with a 5-7″ rainfall. During Harvey we had 30+”, Tax Day flood about 10-12″.
Halloween Scare
The storms which moved through the area on Halloween dropped 2.52″ of rain at the flood gauge station at Cypress Creek and Stuebner-Airline Road over a ~24 hour period. During that time Cypress Creek rose 14′ (fourteen feet). To the west, at the 249 gauge, 2.8″ of rain fell and the creek rose 15′.
True, this left the creek 7′ below top of bank. But the rise was rapid, unexpected and it was only 2.52″ of rain. Clearly the situation along Cypress Creek is still critical. We have this large rise in Cy Creek in this area because Cypress Creek is the longest stream in Harris County and gathers a lot of water in its watershed. The amount of runoff is increasing because of increased development in the watershed (more runoff, less soaking in) and because of the increase in frequency and intensity of rain here on the Gulf Coast. We have no significant detention areas on Cy Creek so the water is forced into the creek for drainage, filling the creek easily. The graph below tells the story:
Nowhere can there be a greater argument for the need for a ‘Third Reservoir’ than here on Cypress Creek. Yet that takes money, money only the State of Texas or federal government has. If you are voting on Tuesday and don’t vote for a candidate who has ‘flood control’ at the top of their ‘to do’ list, you are voting against yourself.
Cypress Creek - Stop the Flooding 