Forgive me, I'm going to get a bit pictorial on you.
Houston has two "reservoirs", both built in the 1930's out well beyond the limits of Houston at that time. I know the area where I live was farmland then; to the west of me (not far) are the grain silos and railroad tracks that took the produce from this land to market. The storage silos now stand as storage for boats and large vehicles; they are too massive to tear down. They are the last remnant of what was a thriving farm community (it was that community which built the church I came here to serve almost 20 years ago now, a church then 150 years old.). Still further west are the two reservoirs. As this article says, they were built to control flooding in Houston through Buffalo Bayou. The reservoirs were built to store water and then release it, in a controlled fashion, into Buffalo Bayou. I can only assume, at the time, that they released over farmland and prairie.
This is the area immediately around this reservoirs today:
That's the area being flooded by the "controlled release" from the reservoirs, a release that, if it isn't done, will see the dams overtopped and even more water flowing out, seeking the bayou and heading south of I-10 (one of the reservoirs is adjacent to the east-west interstate highway that bisects this city north and south).
This is what the spillway looks like that is releasing that water:
Both the Addicks and Barker reservoirs help to prevent downstream flooding of the Buffalo Bayou which ultimately prevents flooding in the City of Houston. The Addicks reservoir is located in between Barker Cypress and the Sam Houston Tollway just north of Interstate 10, and covers approximately 26,000 acres. The Barker reservoir is located just to the south of Interstate 10 and west of Highway 6 and covers approx. 320 acres. Prior to the construction of these reservoirs in the late 1930’s, flooding was a serious problem within the City of Houston.These reservoirs may have contained the flooding, but neighborhoods that were dry before the release, are 4-6 feet deep in water now. The downstream flooding wasn't prevented, merely postponed; some will say, created.
The kind of thinking that praises the reservoirs as gifts of engineering, sadly, predominates in Houston. The Greeks called it hubris, and Aristotle said it was the main engine of tragedy. Whether we in Houston take responsibility for our actions, as a tragic hero does, or whether we shift the blame, as a coward does, remains to be seen.