2019 River/Stream Crossing Reports

Questions and reports related to Sierra Nevada current and forecast conditions, as well as general precautions and safety information. Trail conditions, fire/smoke reports, mosquito reports, weather and snow conditions, stream crossing information, and more.
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kpeter
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Re: 2019 River/Stream Crossing Reports

Post by kpeter » Tue Jul 30, 2019 7:51 pm

MichaelRPetrick wrote:
Thu Jun 27, 2019 8:18 am
I should clarify: I'm not asking about this for GCOT at all, ignore that particular trip. I've a good idea of what to expect and am ready to turn back. Am curious about general stream crossing/melt dynamics here:

I just always read "Be sure to cross dangerous streams earlier in the morning." But every Sierra gauge I've looked at bottoms out late in the day and peaks at midnightish or earlty morning:

San Joaquin near Reds Meadow:

Marble Fork of the Kaweah:

Happy Isles:



Of the above three, only Marble Fork displays something close to the expected flow pattern.

The "delay in melt flowing/making it to lower elevation gage sites" is obviously correct, but I wonder if the usual "cross late in the day" needs a strong proviso about elevation, given that the lower a crossing is, the bigger a catchment basin it's likely pulling melt from, and the more flow there's going to be. The higher a crossing, the smaller it's probably going to be, and while the "late-day-melt" pattern will be true, it'll be at a smaller crossing...

Put as a question: is it the case that heaviest and possibly most dangerous crossings will be the most deviant from the expected "late-day melt" pattern?

EDIT:
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Argh, am screwing up the attachments, sorry! Will fix this evening.
It all depends on the distance between the snowline and the gauge and the speed of the water. As the season progresses, the distances between the snowline and the gauges get longer and longer and this leads to a lag. But the principle is still true if you are crossing a stream somewhere near the snow--it will be lowest in the morning. If you are crossing a stream far away from the snowline the lag could make a different time of day preferable.








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