http://www.houstonchronicle.com/local/gr...172004.php
"...Some have been exceptionally catastrophic as is the case with Harvey, but floods are a regular thing in Houston. This list contains several dozen major floods and goes back to the founding of the city. Some of the early examples are only sparsely recorded, but note the regularity of flooding in downtown in particular.
1837: Buffalo Bayou flooded, with four feet of water recorded on Main Street.
1841: Flooding washed out two bridges over Buffalo Bayou.
1853: Buffalo Bayou overflows its banks causing a major flood in downtown.
1875: Buffalo and White Oak Bayous overflow in the aftermath of a hurricane, washing out all bridges except for one.
1879: Buffalo and White Oak Bayous overflow causing major flooding in downtown.
1887: Buffalo Bayou overflows, washing out several bridges downtown.
Records become significantly better in the early 20th century, attesting to a continuation of this pattern in well-documented storms. In addition to the 1935 flood, major flooding inundated downtown in 1913, 1929, and 1932. Flood-mitigation efforts such as the construction of levees and retention ponds lessened the severity of all but the worst storms after 1935, but tropical storms and hurricanes throughout the 20th century revealed Houston's continued vulnerability to storms.
The reasons have to do almost entirely with topography and geography. Houston sits on the Gulf of Mexico in an active hurricane zone that attracts large storms. But more significantly, Houston's topography is extraordinarily flat. The elevation drop across the entire city and region is extremely modest. Most local waterways are slow-moving creeks and bayous that wind their way through town and eventually trickle into the shallow, marshy Trinity Bay. Drainage is slow on a normal day. During a deluge, these systems fill rapidly with water that effectively has nowhere to go.
...Houston's flood problems are a distinctive feature of its topography and geography, and they long predate any sprawl. While steps have been taken over the years to mitigate them and reduce the severity of flooding, a rare but catastrophic event will unavoidably overwhelm even the most sophisticated flood control systems. Harvey was one such event — certainly the highest floodwater event to hit Houston in over 80 years, and possibly the worst deluge in its recorded history. But it is entirely consistent with almost two centuries of recorded historical patterns. In the grander scheme of causes for Harvey's flooding, sprawl does not even meaningfully register."
