NPS photo
River crossings are one of the greatest challenges in the backcountry.
The water volume, clarity and velocity may vary drastically according to season, time of day and upstream weather conditions. On warm days, melting snow and glacial ice can swell streams that were easily crossed in the morning to flood stage by mid-afternoon. In glaciated areas, hotter, sunny days cause higher volume in the streams due to the ice melt (geologists call this diurnal flux). Voluminous, warm rain is also a contributing factor. Safe footing is difficult to obtain: silty water obscures channel bottoms while clear water allows for slippery algal growth. Icy water numbs feet quickly and even shallow streams are surprisingly swift when flowing down steep inclines. This combination of factors makes stream crossings one of the most hazardous parts of any backcountry experience.