The record flood we had during the winter created several
new obstructions in the creek. A typical
obstruction is composed of dead tree parts.
There may be anything from a full log to a bunch of dead leaves. The material decomposes over time and the
mass looses its integrity. Eventually, another flood deconstructs the
obstruction and carries it on down stream.
Occasionally there’s a different type of situation and the inevitability
of the outcome is not quite so certain.
The key piece in this blockage is a still living tree. The root ball that once perched on a slab of
bedrock just above the bank, slipped off of the rock as a unified mass and
landed in the center of the creek channel.
The bulk of the root system is still enclosed within the
original block of soil. The soil is able
to wick up enough water from the creek to keep the roots healthy and the tree
hydrated. Eventually, the combination of
rain and flood water will wash the soil from the roots. When that occurs, the roots will dry out and
die. There are too many variable
involved to predict just when that might happen.
In the mean time, the tree is growing. There are several healthy shoots developing
from the base. The tree roots that are
in contact with the stream bed will most likely have the greatest
longevity. Basal sprouts tend to have
the greatest chance of surviving on a fallen tree. Conditions may be right to give these sprouts
many years of growth.
At the moment the entire tree is producing healthy growth. Production of new growth increases the
ability of the tree to snag and retain debris floating in the current. The growing tree becomes responsible for a
growing obstruction. Instead of losing
stability as a result of decomposition, the tree and its collection of debris
becomes more firmly positioned in the creek channel. This could result in a drastic and long term
change in the nature of this section of creek.
When a tree goes horizontal, the top of the tree loses its
ability to act as a growth regulator.
Every bud along the trunk is free to make its bid for leader. The rapidly growing sprouts emerge in
clusters that are ideal for capturing small bits of floating debris. If it can maintain life for a couple of
years, the tree will make a formidable barrier.
It’s clear to see that the tree is anchored firmly in
place. The tree held its position
against flood water strong enough to move those slabs of rock. The tree not only stayed in place, it
effectively kept the rocks from moving any farther downstream. If the tree could hold against the record
flood, it should be able to easily maintain itself against the normal high
water levels. This will be an
interesting situation to watch.
Obstructions that are natural in a stream are a good thing. They can slow down the water movement which is the goal. Allowing the steam to twist and turn which allow for the back and forth meandering motions and movement of the stream which is also the goal. Humans have done all they can to straight channel and concrete streams and rivers to the sea. However, the goal should be not to prevent water from returning to the sea as in the case of dams, but allowing every drop that falls on the land to slowly make it's way to the sea, but all the while along the way this slower pathway with all it's various forms of life will benefit from this type of slowed down movement.
ReplyDeleteThe thing to really worry about is the irresponsible behavior of those upstream neighbours who may strip their land, asphalt or concrete it which will fascilitate a more volumuous rapid flow by which nothing benefits and only destroys everything in it's path. The description you've given also will provide more opportunities for wildlife (plant, animal, birds, fish) habitat and future post by you. Looking forwards to it.
Kevin
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Interesting. Is that a Betula nigra?
ReplyDeleteHi Kevin. My creek channels are always changing.
ReplyDeleteHi Dave. I didn't give the best views for identification. It's a American Elm. I did the original ID when the tree was still growing on the bank.
Fascinating.
ReplyDelete