Did the San Jacinto River flooding make the Cypress Creek Flooding Worse?--A HYPOTHESIS

Background

Anyone who remembers Angry Beavers, probably remembers the "big happy"/"little meanie" episode, when the brothers try to dam two different types of rivers. While talking to a park ranger at Mercer Arboretum, my kids and I learned that the descriptions can be applied to Cypress Creek (big happy) and Spring Creek (little meanie). This was because Spring Creek, being smaller, reacted more to conditions of rain and drought. During the Harvey rains, flooding occurred on an unprecedented scale here in the Spring Park Village/North Hills Estates area. Spring Park Village has a very large detention pond that was doing its job collecting rain water from the neighborhood and the nearby shopping areas. This was until Cypress Creek overflowed its banks and filled in the remaining capacity of the detention pond, which then started backing up into the streets. At its deepest, the street flooding was higher than my knee on Monday night (Aug 28th). North Hills Estates was sufficiently underwater in places that relatively large boats were able to navigate among the submerged homes. All of this was Cypress Creek water. Over the next 12 hours, the water receded. Spring Park Village's detention pond was again able to drain the water gathered in the streets, and homes in North Hills Estates that had never flooded before were emptied. The problem: the Cypress Creek water gauge didn't show a significant drop in water level. Spring Creek on the other hand was dropping rapidly.

Hypothesis

South of our location on Cypress Creek is where Spring Creek and Cypress Creek merge into the west fork of the San Jacinto River. Cypress Creek, being the "big happy" naturally dominates the flow between the two creeks, but one has to consider the effect of an unusually swollen Spring Creek with the release of water from Lake Conroe around August 26th/27th [Reference 1]. Did this release cause a flow disruption to Spring and Cypress Creeks? Being that Spring Creek is smaller, is the effect of the disruption more noticeable in its flow? Assuming that a barrier artificial or natural exists in the area where the creeks merge with the river, it's entirely possible that the water pressure from the San Jacinto river caused a back pressure in Spring and Cypress Creeks. This back pressure would impact the volume of water from both creeks that continues to flow downstream. Any disruption in flow to Cypress Creek should cause the water level to rise. That wasn't what the Cypress Creek gauge measured, rather it kept the same height when it reached its peak. Even as Spring Park Village's detention pond filled with water from Cypress Creek, the gauge was keeping relatively the same height. Was the peak height of Cypress Creek more of a measure of the height at which it was overflowing into the surrounding areas? What volume of water comprised this overflow? Why did the flooding water in Spring Park Village return to Cypress Creek while its height did not change much several hours later? Would this overflow of Cypress Creek make the Spring Creek gauge more accurate in understanding the volumetric effect of the back pressure from the San Jacinto River's increased flow?

Did the extra water in the San Jacinto River from the Lake Conroe releases during Harvey cause Spring and Cypress Creeks to backup?

Answers

While we are still in recovery, it will be some time before the events of the flooding are analyzed from a geological/hydrological point of view. The data required include the gauge readings of the various bodies of water, the amount of water released from Lake Conroe, the structure of the various creek walls, beds, and bends, and models for the flows. Engaging in this work is important, not just for developing new local water management and flood control approaches, but also for developing REGIONAL water management and flood control approaches. If the hypothesis is correct, that Lake Conroe's water release into the San Jacinto River caused a significant amount of the flood damage from Cypress Creek, then the sheer cost of the damage demonstrates that a regional plan must be developed. Either the flood plain designations must be broadened for including these non-linear sources, or other release mechanisms need to be developed to address the problem of bodies of water such as Lake Conroe overfilling.

[1] "San Jacinto Rivera Authority reverses course, releasing water", Conroe Courier, http://www.yourconroenews.com/...