This assignment entails detecting geomorphic change of the Feshie River, Scotland, UK by comparing topographic datasets that were surveyed annually and relating that to fluvial processes that have taken place. It is important to note when comparing two topographic datasets that these are single snapshots in time and don't hold information about the entire processes that have taken place.
2003-2004
The Feshie River experienced many geomorphic changes between 2003 and 2004 (Figure 1), the more dominant processes that will be discussed include bar development, bank erosion and degradation.
Figure 1: Feshie River 2003-2004 Geomorphic Change.
Bank Erosion is a process that was prominent in the Feshie River along outside bends of meanders. This process is responsible for significant average vertical lowering (-0.6 meters) as seen in Table 1, but is concentrated spatially. A total of 168 cubic meters of material was eroded.
Table 1: Feshie River 2003-2004 Bank Erosion
Degradation or channel incision was another process that was noted during 2003-2004. This process was responsible for an average vertical lowering of 0.33 meters and eroded approximately 130 cubic meters of bed sediment (Table 2).
Table 2: Feshie River 2003-2004 Degradation
The last process that was measured from 2003-2004 is bar development. This process was responsible for an average surface raising of 0.3 meters, but this was widespread causing a total volume of 212 cubic meters (Table 3).
Table 3: Feshie River 2003-2004 Bar Development
Of the three process mentioned above bar development was responsible for the largest sediment flux, but this was over an area of 728 square meters making the average vertical change the least of the three processes. Bank erosion on the other hand was a spatially concentrated process, but was responsible for the largest average surface lowering of 0.61 meters. Channel bed degradation was moderate in both volume of sediment change and surface change.
2004-2005
The dominant geomorphic changes that occurred in the Feshie River between 2004 and 2005 include widespread aggradation and bank erosion (Figure 2).
Figure 2: Feshie River 2004-2005 Geomorphic Change.
Channel aggradation was widespread between 2004-2005. This is shown in Table 4 by a total area of 7,100 square meters that experienced an average depth of vertical raising of 0.46 meters. This totaled a bed sediment volume of 3,268 cubic meters.
Table 4: Feshie River 2004-2005 Aggradation
The bank erosion that was detected like mentioned early was spatially concentrated at 340 square meters, but had a average depth of surface lowering of 0.97 meters which is a significant depth change in only a single year. This process was responsible for eroding a volume of 329 cubic meters of bank sediment (Table 5).
Table 5: Feshie River 2004-2005 Bank Erosion
From 2004-2005 this reach of the Feshie River experience a net aggradation year. Although there was significant amounts of sediment that were supplied to this reach, not many geomorphic units were created because the sediment blanketed the bed. This sediment will be available for reworking later in time.
2005-2006
The geomorphic changes of the Feshie River from 2005 to 2006 that will be discussed include aggradation and degradation (Figure 3).
Figure 3: Feshie River 2005-2006 Geomorphic Change.
This year was a another year that resulted in net aggradation for this reach of the Feshie River. The aggradation that occurred consisted of a volume of 501 cubic meters of sediment over an area of 1,520 square meters. This resulted in a average vertical raising of 0.33 meters (Table 6).
Table 6: Feshie River 2005-2006 Aggradation
The degradation that did occur was over an area of 735 square meters and eroded 160 cubic meters of sediment. This resulted in an average depth of surface lowering of 0.22 meters (Table 7).
Table 7: Feshie River 2005-2006 Degradation
This was the second year in a row where the reach experienced net aggradation. It should be noted that these data sets don't show what happened between and there could have been moments where this description is a poor approximation.