EIGHTY YEARS OF EROSION AND DAMAGE CAUSED BY DIVERSION OF FURNACE CREEK WASH INTO GOWER GULCH, DEATH VALLEY, CALIFORNIA
Undisturbed Furnace Creek Wash, which drains ~440 km2, begins to steepen about 500 m upstream of the 90° diversion. Gower Gulch, which drained only 6 km2 before diversion, cuts into soft late Miocene siltstone and mudstone; it is over 12 m deep and only a meter wide at the diversion, and plunges 20 m over a 90 m reach to join the much steeper main channel of Gower Gulch. Headward erosion has lowered the wash by 7 m below the pre-diversion level along a series of terraces, with predictable adverse consequences: continually threatening CA Highway 190, which regularly needs reinforcement by gabions and repaving, and encroaching upon the Zabriskie Point parking area. Diversion of stream flow has deprived downstream springs in the wash of some of their recharge. Although the artificial diversion provides some protection to downstream development, significant floods largely bypass the diversion and rampage down the wash, notably in 1968, 1985, and 2004, when 70 percent of the flood waters went on to debouch onto Furnace Creek Wash’s alluvial fan.
Where the mouth of Gower Gulch debouches from the mountain front westward into Death Valley, increased stream flow has not only built an outsized alluvial fan for the size of the gulch, but it has also cut a fan-head channel with vertical sides 6 m deep into the pre-diversion fan. The steep channel walls regularly shed SUV-sized blocks of poorly indurated fanglomerate into the channel, which disintegrate within a few years. Debris flows regularly bury and sometimes rip up Badwater Road. These processes and consequent changes to Furnace Creek Wash and Gower Gulch will remain a case study in geomorphology and engineering geology in decades to come.