Two major flood control projects protect the River Walk. Two miles upstream, Olmos Dam, completed in 1926, holds back the most threatening storm runoff. Some 150 feet beneath this spot runs a three-mile tunnel 24 feet in diameter, finished in 1988 to carry overflow from the dam and other runoff beneath downtown. This dramatic reduction of floodwaters allows businesses along the main channel through the central city to have patios as low as 15 feet above the level of the river without great risk of higher waters.
A new channel dug south beyond this point in 1929 keeps floodwaters from having to negotiate the Great Bend, its path the shape of a sideways horseshoe. When this floodgate drops to send high waters straight past, and when the gate at the south end is also closed, businesses around the bend are almost fully protected from high water. These businesses can therefore be open at virtually the level of the river, an opportunity unusual along most rivers of the world.
Robert Hugman adapted the design of this white stucco gatehouse to correspond with his overall vaguely Spanish design theme. Across the river, the Shops of Aragon were to descend along a cobblestone street—never built—to the level of the river. A flagstone walk was then to cross to this gatehouse, the entry to his imaginary land of Romula, a mixture of river level parks and commerce. The rounded arches are topped by a walkway with an open roof of cedar posts that create shadows on the wall of stucco and columns that hides the raised floodgate.