Tuesday, December 22, 2015

So What about the Minto Bridge in High Water?

Ever since the January flood of 2012, it has been an interesting question - indeed something of a hobby horse here - to ask how often the Minto Bridge would be closed.

Inset, the river at about 19 feet on the 17th
Main photo, the river at about 25 feet on the 19th
This really only mattered because there was a period when the City was making crazy exaggerated claims for the bridge and trail as a transportation corridor for commuting and errands.
It is expected up to 14 percent of residents will use the route for commuting, representing up to 21,700 non-automobile commuters. - Minto Bridge and Path Master Plan.
That's puffery that bears no plausible relation to reality.

So for a time it seemed necessary to critique it. Fortunately the City backed off and mostly the Minto Bridge is properly framed up as a recreational amenity. The moment has passed, but the question about seasonal closures remains interesting because it's not talked about enough.

So this is basically just trivia, but it's still interesting.

And now that we have some high water, we can add more data! (Previous discussion here.)

Water level and trail closure starting at least by the 10th
(Closure sign and observation via Hinessight)
Historically, depending on ground saturation and previous flooding, trails have started closing at river levels between 15 and 20 feet.

This year it started for sure at about 18 feet by Thursday, December 10th - though it may have started earlier. Based on the river level, trails probably started being impacted on the 8th.

Now, with the river rising well above 20 feet (to peak at about 25 feet), the City closed the whole park on Friday, December 18th.

It happens that the construction webcam can give us a visual for more direct evidence. 

You can see (at top) how the berm on which the path will sit was fully exposed on the 17th. But by the 19th, it's just a thin ribbon, barely above the water!

So even high water that is shy of official "flood stage" (at 28 feet) is going to affect the use of the bridge.

The soccer fields at Wallace Marine Park in January 2012
(This peaked a little over 29 feet)
The river's back down to about 21.5 feet now, and it looks like it's going to stay there for a few days. So even if the City opens the park, most of the trails will be closed for a bit yet. It will likely be true that the path won't have been usable for "most of December." 

As long as the trail and bridge isn't being positioned as a key commute corridor, this seasonality doesn't matter. As we see with the Union Street Railroad Bridge, the ability to look out over the water, to experience safely in this way the rise and fall of the river in season, contributes to an important sense of connection with the natural environment. The river is absolutely central to Salem as a place, and we lost much of that connection in the second half of the 20th century. Anything that helps to restore it is a good.

To say the bridge will be out of use for a few days or weeks each year doesn't mean the bridge is wasteful or extravagant. By giving citizens who are not personally affected by flooded basements and yards - or even greater catastrophe - a more direct link to seasonal variation in water level, it might actually help ground our conversations better in nature and with real regard for how it affects other policy and funding choices we might make. With this small limit, it will also highlight the glorious days of summer even more, and perhaps enhance our total enjoyment of the bridge, helping us appreciate it even more.

There will be many days like this
Summer/Fall 2015, via City of Salem and Ron Cooper
You know, as a postscript it might be useful to clarify that the bridge deck itself is several feet above "ordinary" high water and a few feet above a 100-year flood, which is about the same as the 1996 flood, several feet yet higher than the 2012 flood. The primary impact is to the path system on Minto, not the bridge itself.

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