This past month we have been busy with tree planting and doing more stream surveys to line up our coming activities for the next few months. Bloods Creek has seen some flooding since the last snowfall though no major disruption to the habitat has occurred. Knarston Creek’s flood control structure seems to be alleviating the flooding for those that live downstream of Lantzville road while in the upper watershed some small erosion sites have been identified and will get some attention over the next month or so.
Small erosion sites are a natural process of stream morphology [fluvial geomorphology to be technical]. What this means is that when you look at a stream you tend to see it in a relatively stable state but unless in flood state you do not tend to see how the hydraulic effect of flowing water is changing constantly what we term as the stream bed and banks. Small particles are constantly being eroded from the banks and the streambed as the water flows downstream. Consequently small particles of suspended sediment are constantly flowing downstream, depositing when encountering barriers. These barriers can be as small as gravel and as big as log jams. Good old gravity tends to allow the banks to ever so slowly creep down allowing for the water to carry away material. This can also occur when wildlife [or humans] cross the stream eroding the banks. Even the action of small animals burrowing into the banks to create homes or in the search of food creates erosion. So as you can see erosion is a natural occurrence of a healthy stream environment. Nature’s way is to grow plants where by the roots can hold the bank material in place slowing the erosion process down.
When we find eroded banks we have to assess whether it needs some plants or do we just leave it. If we decide to intervene we will do what has become called Bio-Engineering, which is the use of plant’s to remediate erosion sites as apposed to bringing in machinery and loads of rock to armour the banks. Over time we have realised that plant’s will do a more natural job of alleviating the erosion than riprap. Rocks tend to be the hard engineering solution so often used because it is easy and satisfies our need for control of our environment. Using plant’s on the other hand is working with the ecosystem using its own methods to help to heal the site while providing habitat and as we often find out when using Willow providing food for the Beaver.
One of our first Willow plantings was at a site used to transport logs across a stream from a small clear-cut, as you can imagine this made a big mess. We went in and drove stakes into the banks and wove branches much like basket weaving. This provided a vegetative barrier to the forces of the flow while softly dissipating the energy against the banks. Rip-rap was all we heard, that is the only way to go; well, within a year the stakes had taken and the weaving had collected sediment [Barrier] and along with the planting of trees we achieved bank stability without the ugly look of rip-rap – which in most cases tends to bounce the energy of the water around the channel usually creating more erosion downstream.
Back to the Beaver; he or she taught us our first lesson in planting Willow stakes. Shade being important to the stream we had left most of the stakes full length with about 3 feet in the substrate and a equal amount or more above grade. Along came the Beaver and chewed off all the stakes down to around a foot tall then left them alone. What he or she had done was limit the vegetative growth above ground while allowing the roots to fully form without the desiccation [drying out] of the stakes by having too much growth on top. I personally think he or she was thinking of the lovely lunches all that new growth would provide over the following years.
March will see the return of the Herring to our shores, which will hatch out just in time for our young Salmon who will be leaving their natal streams. The young Herring will provide a huge biomass of food to help them grow into healthy Wild Salmon before heading out further into the Pacific to complete their life cycle.
April will be the month we will cleanup upper Knarston. The date and time will be in the April Log, hope to see you there.