Logjam Alert! Be Extra Careful on Colorado Rivers

Look what's happening on the Colorado River. If you're planning to float the river, please be extra cautious and keep an eye out for this danger.

The Mesa County Sheriff's Office shared a Facebook post with photos of this hazard. This logjam has built up in the Horsethief section of the Colorado River in McInnis Canyons National Conservation Area. The attached photos are near the Black Rocks 7 campsite.

First off, what's a logjam, and what causes them? According to Wikipedia:

A log jam is an accumulation of large wood (commonly defined as pieces of wood more than 10 cm (4 in) in diameter and more than 1 m (3 ft 3 in) long^[1] also commonly called large woody debris) that can span an entire stream or river channel.

Wikipedia goes on to say, "Log jams alter flow hydraulics by diverting flow towards the bed or banks, increasing flow resistance and creating upstream pools, diverting flow onto the floodplain and damming the channel causing water to spill over the structure."

So, what's the danger associated with a log jam?

The formation of a log jam against one bank typically concentrates flow in the wood-free portion of the channel, increasing velocity through this section and promoting scour of the riverbed, the formation of channel-spanning log jams can lead to the formation of an upstream pool, water spilling over the structure generating a "plunge pool" immediately downstream.

The Mesa County Sheriff's Office recommends using caution when boating the river, and encourage you to always wear a personal flotation device, especially during spring runoff.

Special thanks to Shaun, a Grand Junction BLM River Ranger, for the photos.