Interior Secretary Ken Salazar recently announced plans to create more man made floods of the Colorado River in the Grand Canyon. This reverses the Bush Administration policy that allowed one high water flow event on the river in 2008 to be followed by long periods of consistent flow.
The importance of this change in policy has to do with the effect that the Glen Canyon Dam (and the creation of Lake Powell) has had on the river ecosystem in the Grand Canyon. Since the completion of the dam in 1966, the beaches in the Grand Canyon have slowly been eroding away due to the lack of silt and sediment flowing downstream. The sediment that used to flow into the canyon is now being deposited in Lake Powell and now the only major influx of sediment comes from the Paria River and Little Colorado River drainages.
Hermit Rapids during Grand Canyon Flood - March 2008
My understanding of the planned flooding is that it helps to move these sediments further downstream to restore not only beaches but the sand bars that are the habitats for the endangered humpback chub.
The planned floods also help to remove invasive tamarisk plants from the banks of the river. This non native species has rapidly overtaken native plants in beach areas and has become such a problem that each year crews physical remove them from certain areas along the river.
The idea of a flood may sound dangerous to hiking and rafting the canyon and that more frequent flooding will prohibit these activities. I personally know this is not true since I was leading a backpacking tour in the canyon when the last flood (the technical term is ‘high flow event’) occured in March 2008. Our group was camping at Hermit Rapids that night and the water at it’s highest point came up the beach about 20 to 25 feet which still gave us plenty of space to camp. We even saw a rafting trip hit the rapids when the water was at it’s highest point.
The controlled flooding will not take place immediately and no timetable has been put in place yet.
