Open Letter to USFS: Improved bridge at Ramona Falls

[eflister]

hello! people grabbed onto that detail even though it wasn't at all my intended emphasis. my point was that both bridge design and hiker awareness/warning signs should take glacial phenomena into account. independent of the particulars of the recent tragedy (there's no evidence that rain didn't melt ice dams, releasing reservoirs of pre-existing melt), such precautions would improve safety even for cases of non-glacier-related flooding.

anyone know non-glacier related causes of the "sudden flushing" described? just sudden changes in the precipitation volume itself?

[pdxgene]

I'd still like to hear some good reasons why Ramona Falls should have a permanent bridge when the trailhead isn't even accessible for a good chunk of the year and you have to park behind the gate at the Sandy River..
Is it really a good idea to encourage people to do this as a 12+ mile roundtrip hike on short days in winter conditions? I'm sorry but I've seen way too many unprepared people back there even in spring. The snow can go from nothing at the crossing to 3-6 feet deep in a quarter mile on the other side of the Sandy. This is not a winter hike for the casual hiker like it is in the summer. And if you are prepared, you won't need the bridge.

[Water]

I have seen a creek high in the south san juan wilderness around 10,500-11,000ft~ (surrounding terrain topped around 12,500 and was a relatively small watershed (six square miles?)) in Colorado surge as it rained. This was in late September and a gulf of mexico tropical storm had sent up tons of moisture. There are no glaciers there but the rain truly came down like cats and dogs at several times between otherwise consistent rain and each time it did the river went nuts. It surged if you will, suddenly.

I imagine the catchment area for the sandy is larger than this place in Colorado (above platoro reservoir, near conejos river) . A thunderstorm cell unloading due to orographic lift would be very capable of making a stream surge. The lift between the bridge on the Sandy and on up is dramatic--decent rain rate at the bridge could be a rate of 5-10 inches an hour up higher on the mountain (obviously not sustained for an hour).

while we did not hit an event like this (which happened in the fall of 2006) here is some hard data on the precip potentials for mountain rain in our area,
http://www.turns-all-year.com/skiing_sn ... topic=5474

[raven]

The catchment area above the seasonal bridge is less than 2 square miles -- to the top of the mountain -- as I eyeball the map.

[Water]

i get

"Area is 11.95 km², 4.61 mi²" when I measure above to top of mountain... using caltopo. That made me curious about my off the cuff number of the area I hiked in the south san juan wilderness. measuring the rough catchment area there (keeping to contours) I get Area is 8.04 km², 3.11 mi². So the hood area is at least a mile bigger..and certainly has more relief/orographic potential.

[raven]

To get that number, the catchment basins of the Muddy Fork and Rushing Water Creek would have to be included. As I understand the placement of the washed out the bridge, it was upstream of both tributaries.

Also, greater vertical relief provides less time for the waters to be resident because they would flow faster. And any flows that reached snow fields would drain be retarded.

[Water]

i think you have your terms mixed up? upstream vs downstream. The bridge is located below the confluence of rushing water creek and the sandy river, but of course well upstream from where the muddy fork joins the sandy. it would physically be impossible for a single bridge to be located upstream of two tributaries, if it spans a section after where they confluence.

the greater relief supports my argument...both that orographic lift can squeeze crazy amounts of water out, and if you have a 2² mile area of high relief and it all funnels into a single channel (key here..it isn't all going onto a flat field to spread out) that is much less vertical and much more horizontal, but still has a good gradient and channel...it will dramatically increase flow.

[raven]

Water, the bridge is within the wilderness area; your map shows it outside the WA. I confess to not knowing where to find at the moment an accurate map depicting the bridge in question, the PCT routing and the wilderness area.

Yes orographic lift can drop a large amount of water, but in my experience cumulonimbus have delivered more on my noggin over short intervals in several states than any storm I have been in the Cascades or the Olympics. I'm not talking per day or week, I'm talking per minute.

Nearby measured rainfall for that day -- the only day with rain reported around then:
Blazed Alder Snotel to the west -- .6" reported
Red Hill Snotel N (Vista Ridge) -- 1" reported
Mt Hood test Snotel S -- .8" reported

This was not a particularly fearsome storm.

[kepPNW]

Water, the bridge is within the wilderness area; your map shows it outside the WA. I confess to not knowing where to find at the moment an accurate map depicting the bridge in question, the PCT routing and the wilderness area.

That map looks entirely accurate, except for the Wilderness boundary. Green Trails shows the Wilderness way back by the parking lot...

[Charley]

Funds and wilderness its doable. We have heard all the stuff about wilderness obligation I'm not preaching government take care of all just build a bridge its not welfare and a free ride.

Money and trees is not necessary it's bridge has worked fine years nobody died was not raft government not have to baby everyones.