Wednesday, May 30, 2012

Tree Down but not Out

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. 


  1. 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.

    The 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.



  2. Interesting. Is that a Betula nigra?

  3. Hi Kevin. My creek channels are always changing.

    Hi 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.