Monday, April 25, 2011

Bridges vs. Floods

There hasn’t been any snow for awhile, but we’re far from getting any relief from the weather. Now we’re in a pattern of rain storms coming through every few days. Saturday’s storm dumped 3.4 inches of rain on top of already saturated soils and the resulting flash flood rose to set a new record. One of my concerns during times such as these is the security of my foot bridges spanning the creek.

After the record setting floods of 1997, this bridge was relocated and elevated to keep the bridge deck above the high water mark. The accumulation of debris shows that the bridge was submerged for at least part of the recent flood event. Fortunately, the flood water wasn’t strong enough to move it from this position.

This bridge didn’t fare quite as well. It looks a mess, but things aren’t really as bad as they appear.

The bridges are intended to move with the flood water. Each bridge is tethered to an immovable object. When the water rises, the bridges float up and lay themselves along the bank. The restraining cable can be seen attached to the lower right-hand corner of this bridge. Repositioning the bridge is much easier when it’s still at its proper site rather than a quarter mile down the creek.

My options in a situation like this are to either let the bridge move during a severe flood or elevate it above the high water level. Elevated bridges make it difficult to cross with DR Brush and still require maintenance of the approaches after a flood. Anchoring the bridge in place doesn’t work because the immobile bridge causes the creation of plunge pools, bank erosion and channel redirection such as you would get when a tree falls across the channel. Bridge movement is a rare occasion, so it’s not something I have to deal with very often.

At its peak, the flood water completely covered the level ground between the hills. The leaves that weren’t washed away, ended up plastered on the bases of the tree trunks. It’ll take a little while for the plants to upright themselves.

This bridge on a smaller tributary is intended to stay in place. The rock bottom of the stream is immune to plunge pool development and rock in the banks makes the whole site fairly stable. Strong storms are predicted through the middle of the week, so the bridges may get hit again. I’ll wait until things dry up a bit before putting things back where they belong.


  1. Hi Steve...looks like you have bridges over troubled water!!
    Gee you really are getting plenty of rain. We are wet, but nothing like you down there!!
    It probably will dry up and the ground will be like brick!! Its always something!!!

  2. Hi, grammie g. At least the well is full and there's plenty of water for a shower when I get muddy. A summer drought certainly wouldn't surprise me.

  3. And Steve, please be careful out there . You surely have been experiencing the same high quantities of rain as the SW corner. The ground is super saturated,beyond what Iv'e seen in along time.The other day a 100 ft plus tree,gave way at a rotted hollow section and came down while I was in the woods, not 50 yards away! Right now, even a small breeze has enough strength!When I went back 2 days later to view some white trilliums there ,another mammoth tree had fallen , roots and all,aswell!Watch the cut banks and the steep slopes!If you get time see my "look out below" post!
    sorry ..posted this on your fly blog from the 24th by have so many interesting things going on I forgot for a second which one I was reading!

  4. Don't worry, Michael. I've been around long enough to learn when to be cautious. I enjoyed your blog. I was especially interested in your work with milkweeds.