Lynn Canyon Changes

¶ … Stream Channel Lynn Canyon Changes in the shape of the stream channel The study of the canyon is best done as was in this case during the winter, spring and summer when the water levels are low and most of the features are exposed for observation and study, and also the safety of the Canyon is more assured than during the heavy rains.

In autumn, there are heavy rains and also during the peak snow, the melting snow in spring results in high water levels that may ultimately obscure some of the stops that are lower in latitude.

The concentration of this section will be on the river that flows on the bed of the Lynn Canyon and the physical features it has, the direction and change of its flow as well as the evidence that exposes the ages of changes that the river has undergone in terms of the direction, force and the size. The stream within the canyon kept shifting the channel over the years due to the presence of large boulders.

In some places, the stream is observed to flow around elongated boulder ridges within the channel formed during the higher flow stages. Across the stream and up the stream, it is observed that there is a boulder surface that keeps a forest alive of 10 m trees from the east bank of the stream. Further down the stream, the river flows round an island with larger trees and the banks are a lower layer of boulders covered by a layer of sand.

The forest along the stream is a mosaic of patches made up of trees of different ages. The age of each patch of trees indicates the date that this region of the stream was an active bar in the channel of Lynn Creek. The river channel is also observed to be changing its position and at times the river would abandon the channel and migrates away from a position. This is evidenced by the variable age of tress along the stream and in particular along the floodplain (Bob T.

& John C., n.d). There is also evidence of the banks being eroded and this can be seen through the steep yet un-vegetated and the stream flows near its base and there are also trees that have fallen into the river from the bank due to under-cutting the bank. There is also lacking vegetation, meaning the river had flown through this region. The stream flow fills several channels across the floodplains.

It was also observed that upstream, the river cuts a narrow canyon into the bedrock and downstream it broadens and splits as it flows through a floodplain. Upstream, the surface of the bedrock is above the creek level and Lynn Creek has only been able to cut a narrow canyon through this hard rock. Downstream, the bedrock surface is buried and here the river has cut a much broader valley in the much softer, thick sediment that overlies the bedrock.

These sand and gravel sediment are visible in cliff of the Canyon mouth. Fig. 1.0 The sketch of the Canyon. Within the Canyon, the flow of the river majorly runs between the narrow walls. This kind of concentrated flow has caused a deep pool in the gravels at the mouth of the canyon. The scouring of these pools happens mostly during floods when the energy of the river is highest. As the waters spread down stream, they lose energy and the pools tend to be generally shallower towards the downstream.

The absence of vegetation along the cliff is a clear indication of the active erosion that takes place especially during floods when the water levels rise and lap up against the cliff. During the floods, the boulders are brought downstream by the raging waters. This activity also brings downstream gravel and sand most likely from all the way up at the Burrard inlet.

The presence of boulder layer at the top of the cliff which are similar to those in the canyon is an indication of the ancient level of the river at the times when the river flowed at that high level and the flat surface was the ancient floodplains before the river curved the surface to be at the lower level it is today.

Evidence of glaciation in the Canyon The Lynn Canyon has spectacular geographical features with the canyon presenting the major glaciation processes and at the base of the canyon a Coast Mountain Range that was formed due to volcanic activity that is estimated to have taken place 10 million years ago. Then the isostactic adjustment also further raised the volcanic range to be above the sea level hence completing the orogenic process and the exposed igneous dike is an evidence of this (Geocaching, (2013).

This presents a unique combination of numerous geographical activities in the same region. Following the formation of the coast range, there occurred three glacial and inter-glacial periods that eroded the coast range to the present form. The Lynn Canyon underwent three significant periods of glaciation with the recent one that shaped it to the current status taking place 20,000 to 10,000 years ago.

It was during this period that the U-shape valley of the canyon was formed, changing the previous nature of the North shores that used to be large bays and had high elevations. This was as a result of a 2km thick ice and one of the evidences of this glaciation are the erratic rocks that were picked up and deposited along the canyon as the glacier moved into the Pacific ocean.

Yet another evidence of this glaciation is the deposits of till and peat that are located near the suspension bridge (Geocaching, 2013). Apart from the U-Shape valley, there are other evidences of the glacial activities such as the deposition of the glacial till as.