Apr 9, 2013 at 11:08 pm #1301515
@ryanLocale: Northern Rockies
Companion forum thread to:Apr 9, 2013 at 11:48 pm #1974753
Travis LeannaBPL Member
Thanks for this, Ryan. Judging what a stream or river will be like, especially with snowmelt in spring, can be incredibly tough. While I'm not sure *how,* I think this is a subject of backcountry travel where more research can be done.
I agree that the NOHRSC website is very useful for winter snowpack and many other aspects of backcountry conditions. Another potentially useful filter on the NOHRSC is the "snow melt" found here: http://tinyurl.com/cjo6krb
The NWIS database is also good for checking streamflow, as is this website: http://www.americanwhitewater.org along with a few others, as I'm sure you're familiar with.
I'm currently frustrated with this cold spring. I had anticipated doing some Wisconsin whitewater (YES we actually have that!!!) by now, but the good rivers are still frozen. Grrrrr.
EDIT: FOR ANYONE LOOKING AT THE NOHRSC WEBSITE, INCLUDING MY LINK, MAKE SURE TO CHECK THE DATE AND UPDATE THE MAP. THE WEBSITE IS NOT SELF-UPDATING.Apr 9, 2013 at 11:59 pm #1974755
John WittBPL Member
@johnbrown2005Locale: Portland, OR
Great stuff. Most useful piece on BPL in a long time. Many thanks.Apr 10, 2013 at 8:21 am #1974826
Luke SchmidtBPL Member
@cameronLocale: Idaho Falls
Great article. I don't have a packraft (yet) but this is the kind of article I would come back to if I ever get one.
Actually I thought of another application for this information. I'm looking a some trips in the Wind River range and the Teton Wilderness. Using your ideas I could make a rough guess as to whether certain rivers could be safely forded or not.Apr 18, 2013 at 11:15 pm #1978286
Rex SandersBPL Member
@rexLocale: Central California Coast
More short-term streamflow variables to consider for snowmelt or glacier fed streams:
If snow pack air temperatures are cycling above and below freezing, you could see significant daily rises and drops in streamflow. If you arrive at the creek early in the morning and the flow looks too low – wait a few hours, you might be rewarded as the day warms up and the snow melts. Conversely, a flow that's just right, right now, might be too high for comfort in a few hours. The air temperatures at the elevations of the snow pack control melt rate, not air temperature where you are standing.
The directional exposure of a snow pack can make a big difference. If the snowpack of your favorite creek is in a sheltered, north-facing bowl or cirque, you need higher air temperatures to melt that snow, than a similar creek with south-facing snowpack (in the Northern Hemisphere). If you are comparing one creek without a gage to another with a gage, you should take snowpack exposure into account.
You might not see that first pulse of snowmelt until several hours after snow pack air temperatures go above freezing. More miles below the snow pack, gentler gradient, and lower temperature rise, mean longer waits. In some cases, the peak flows might be in late afternoon or early evening.
The weather just before and during your trip can play a big role. Warm weather will speed up snowmelt. A warm rainstorm can really speed up snowmelt – the worst flooding in California's Sierra Nevada mountains comes during and shortly after warm rainstorms on big snow packs. A cold snap can reduce streamflow to a trickle. You can see these patterns on nearby streams with gages; you should see similar patterns on your favorite creek. Spring weather forecasts in the Western USA can be notoriously inaccurate, so you should learn to make your own short-term weather forecasts based on observations and local knowledge.
On the other hand, streams and rivers which are primarily fed by springs, like some in Oregon's Cascade mountains, might have none of these issues. Once the river thaws, flows can be quite steady, regardless of the weather, time of day, etc. Snowmelt feeds these streams, but the pulses are filtered by running through miles of porous volcanic rocks and soils before surfacing in springs.
— RexApr 25, 2013 at 10:49 am #1980432
Dan DurstonBPL Member
As mentioned, having an idea of the decent rates for a watercourse is valuable. Using a topo map is a good way to do this, but Google Earth also provides another neat tool.
Using the ruler function, trace a 'Path' of the river. When finished, save the route and then right click 'show elevation profile'. Here's one for the first 4 miles of the NF White River:
From this, one can easily calculate descent rates and you also get a good visualization of the route. Descent rate consistency becomes obvious, and steeper sections (ie. 0.6km, 3.5km) are apparent. Since this elevation data is linked to the satellite images, you can then take a closer look at any areas of abnormal elevation drop.
Of course this is only as good as Google's data and your tracing of the route.
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