Houston, Texas, seat of Harris County, has a long history of flooding because the city was built on a flood plain. The deluge generated by hurricane Harvey in August, 2017, is only the latest episode.
Houston lies within a coastal plain about 50 miles northwest of Galveston. The area has very flat topography which is cut by four major bayous that pass through the city: Buffalo Bayou, which runs into downtown and the Houston Ship Channel; and three of its tributaries: Brays Bayou, which runs along the Texas Medical Center; White Oak Bayou, which runs through the Heights and near the northwest area; and Sims Bayou, which runs through the south of Houston and downtown Houston. The ship channel goes past Galveston and into the Gulf of Mexico.
The land around Houston consists of sand, silt, and clay deposited by local rivers.
The sedimentary layers underneath Houston ultimately extend down some 60,000 feet, with the oldest beds deposited during the Cretaceous. Between 30,000 feet and 40,000 feet below the surface is a layer of salt, the primary source of salt domes which dot the metropolitan area. Since salt is more buoyant than other sediments, it rises to the surface, creating domes and anticlines and causing subsidence due to its removal from its original strata. These structures manage to capture oil and gas as it percolates through the subsurface. [source]
Groundwater pumping also causes subsidence in parts of the city. (See: Geologists find parts of Northwest Houston, Texas sinking rapidly )
Hurricane damage in Houston:
As described by the Harris County Flood Control District (HCFCD) [link]:
When the Allen brothers founded Houston in 1836, they established the town at the confluence of Buffalo and White Oak Bayous. Shortly thereafter, every structure in the new settlement flooded. Early settlers documented that after heavy rains, their wagon trips west through the prairie involved days of walking through knee-deep water. Harris County suffered through 16 major floods from 1836 to 1936, some of which crested at more than 40 feet, turning downtown Houston streets into raging rivers.
Houston was flooded during the September, 1900, hurricane which wiped out Galveston.
In December of 1935 a massive flood occurred in the downtown Houston as the water level height measured at Buffalo Bayou in Houston topped out at 54.4 feet which was higher than Harvey. There have been 30 major floods in the Houston area since 1937 when the flood control district was established in spite of construction of flood control measures.
In June, 2001, Harris County suffered widespread flooding due to hurricane Allison. According to HCFCD, before leaving the area, Allison would dump as much as 80 percent of the area’s average annual rainfall over much of Harris County, simultaneously affecting more than 2 million people. When the rains finally eased, Allison had left Harris County, Texas, with 22 fatalities, 95,000 damaged automobiles and trucks, 73,000 damaged residences, 30,000 stranded residents in shelters, and over $5 billion in property damage in its wake.
Some climate alarmists are claiming that global warming has played a part in the flooding produced by hurricane Harvey. Dr. Roy Spencer debunks that notion here and here. Storms of or greater than Harvey’s magnitude have happened before. Storm damage is not due entirely to weather. Some is due to local infrastructure.
It all boils down to the luck of the draw: if you choose to inhabit a flood plain, you will get wet from time to time.
P.S. Prior to Harvey, which made landfall as a Category 4 storm, the U.S. had gone a remarkable 12 years without being hit by a hurricane of Category 3 strength or stronger. Since 1970 the U.S. has only seen four hurricanes of Category 4 or 5 strength. In the previous 47 years, the country was struck by 14 such storms.