Thursday, November 18, 2010

Up the Creek

The upper reaches of the creek aren’t looking much like a creek. The ongoing drought has left this segment without water for four months. Vegetation has covered the banks and leaves have hidden the creek bed. Topography is the only readily visible sign that there could be a creek here.

The creek channel winds its way through the floodplain area. During flood events the water will spread completely across this low area and the meandering channel won’t be evident. To the left is a steep little rise that steps up to another nearly level area. In the distant past, this would have been a flood plain area. Over the years, the creek has eroded a channel deep enough that the old floodplain is left as a terrace high enough to avoid being covered by water. Once freed from flooding, the terrace began to develop a plant community that was different from that in the floodplain.

The invasive Bush Honeysuckle remains green much longer than the native forest vegetation. I was through here two years ago killing honeysuckle. No matter how hard I search, it seems I always miss one or two plants. In my defense I must point out that the bush would have been about half this size two years ago, so it would have been more difficult to see. I’ll be back this winter to remove this guy.

I’ve shown how fallen trees can cause a bank to erode more quickly, but this seems to be an example of the opposite effect. The trees fell so the root masses actually protected the bank and made it more stable than other areas.

This cut bank gives a perfect opportunity to see the composition of the terrace soil. The rock has been visible for several years and will eventually fall into the creek channel. The creek channel has actually begun to move away from the bank and the lower part of the slope is beginning to stabilize. I like to visit here frequently to see what interesting artifacts come to light.

Eventually the steep bank will come to resemble this, minus the tripod tree. Once the creek channel moves enough that the water stops removing the loose material at the base of the slope, plants will colonize and hold the soil in place. The vertical bank will continue to fall away and eventually develop a slope gentle enough for vigorous vegetation to cover the surface. This tree once grew on the top of the bank, but lost soil from around the roots as the bank transitioned from vertical to gently sloping. The tree and bank are both perfectly stable now.

I found this water hole hidden beneath a log jam. It’s not easily accessible, but the deer have found a spot that allows them to get a drink and they’re beginning to develop quite a mud hole. We just had eight tenths of an inch of rain Tuesday night, so there may be one or two more water holes today.

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