Central Texas is no stranger to widespread damage caused by flash floods. But the recent July 4th flooding along the Guadalupe River shocked the world because of its appalling toll in human lives. While such events can teach important lessons about how to prepare for the next disaster, it can sometimes take many avoidable tragedies before the necessary steps are taken. My hometown of San Antonio, which averages more than 30 inches of rain a year, is a case in point.
To understand these flooding phenomena, one must pay close attention to regional topography. In a recent article titled, “Could the San Antonio River ever have a flood as catastrophic as the Hill Country?” San Antonio Express-News meteorologist Anthony Franze explains that “[t]he Guadalupe River is located along the Balcones Escarpment, which is characterized by steep slopes, thin soil and thick limestone. This environment often results in intense, fast-moving runoff into the Guadalupe River and its tributaries.”
Historian Char Miller describes the Balcones Escarpment as “a geological fault zone that runs for roughly 450 miles … [and] is critical in several respects. It demarcates the southern terminus of the Great Plains … [with] some sections of the … landscape … as high as two thousand feet … The land that slopes away from the fault line toward the Gulf of Mexico is the southern coastal plain. The reciprocal relationship between these two masses and longstanding climatological patterns can produce wild swings in local weather.” In his book titled West Side Rising about the 1921 flood that nearly destroyed San Antonio, Miller also portrays the Gulf of Mexico as a “trigger mechanism” for flooding events. “If [the Gulf’s] bath-water warm, moisture-laden air pushes onshore, the flow will slowly lift with the rise in elevation. Once it reaches the escarpment the uplift is more abrupt, forcing the moist air to interact with colder temperatures above. The moisture condenses, the cooler air falls, then it is warmed and rises again, a cycle of convection that can result in major thunderstorms.” According to Miller, these thunderstorms and the “blockbuster floods” they generate are why the National Weather Service coined the phrase “Flash-Flood Alley” to refer to San Antonio and the greater Balcones Escarpment watershed.
The Spanish who arrived in the area around the feast day of Saint Anthony of Padua would have been ignorant of these dynamics and their impact on the lazy river where they would establish San Antonio. In fact, “with little sloping terrain to hurry its flow, the San Antonio River follows an erratic course which led one of its early names to translate into ‘Drunken Old Man Going Home at Night,’” according to author Lewis F. Fisher in his book Crown Jewel of Texas, the Story of San Antonio’s River. Fisher points out that “San Antonio may have been nurtured within the folds of a life-giving river’s bends, but there came a price” because of the enormous drainage areas surrounding the town. These include the “San Pedro Creek, which drains an area of some three square miles … [and] also receives floodwaters from the twenty-three square miles of the normally dry Apache, Alazan, and Martinez creeks’ drainage area.” In addition, the San Antonio River “catches surges from storms over a dry drainage bed known as Olmos Creek which drains an area of 34 square miles just north of the historic center.”
Over time it would become apparent that San Antonio’s Spanish founders failed to understand the nature of the terrain when they sited the “streets, plazas, and residential areas … within the embrace of two waterways, the San Antonio River on the east and San Pedro Creek to the west,” according to Miller.
Perhaps the finest geographical description of this “embrace” is also provided by Miller: “[T]he San Antonio valley lies within a web of rivers, streams, and creeks. Imagine a handprint, with San Antonio as the palm. Like fingers, five major waterways define the riparian relationship between the low hills to the north and the flatlands below. From east to west, these systems include Cibolo and Salado Creeks, Olmos Creek and the San Antonio River … Leon Creek, and the Medina River. Each is fed by the crystal-clear waters of the Edwards Aquifer that bubble up from its springs, bogs, and wallows; each ultimately merges with the San Antonio River … When rain falls, they can rise quickly, powerfully, and fatally.”
Despite the horrors of numerous deluges, major flooding in the 19th and early 20th centuries seems to have occurred at intervals just long enough to lull people into forgetting the dangers. According to the American Society of Civil Engineers, “Serious flooding of the San Antonio River occurred in 1845, 1865, 1880, 1899, [and] twice in 1913.” And yet each time –– incredibly –– city leaders found their fear of rising water outweighed by a fear of the potential costs associated with taking appropriate action. This mindset will sound eerily familiar to contemporary residents of Kerr County. Perhaps eeriest of all is the hydrological study completed in 1920 warning that another severe flood was inevitable. “When such a flood will recur, no man can say,” the study’s authors wrote. “But that it will recur is certain.” The very next year, San Antonio was hit by its most devastating flood to date, killing more than 50 people and wreaking havoc on the city’s residential west side and downtown business district.
The next issue of Our Water Matters will explore San Antonio’s response to the 1921 flood, a response that would eventually culminate in the construction of Texas’ top tourist attraction and an engineering marvel: the San Antonio River Walk.
Trey Gerfers serves as general manager of the Presidio County Underground Water Conservation District. A San Antonio native, he has lived in Marfa since 2013 and can be reached at tgerfers@pcuwcd.org.