Introduction

Information Sources

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Appendix 1

Bibliography

In the wide valley floor of the Old Crow River, the river bed meanders from one side to the other, alternately cutting and filling in the sinuous channels. Morlan (1973) describes the process of "point-bar formations" which occur at some of the meanders in which a point of land extends like a finger into the inside of the river bend while a gravel bar develops on the opposite bank (Figure 1.5a, Figure 1.5b). At other meanders the bar is found on the inside of the bend opposite a low, slumping wall being cut on the outside bank. The cut banks and points of land are composed mostly of finely stratified layers of silt and sand. Modern, active ice wedges can often be seen in the cut banks where overhanging mats of vegetation protect them from direct sunlight. Oxbow lakes and sloughs are abundant in these valleys, and long, nested rows of meander scars can be observed from the air (Morlan 1973)

Figure 1.5b Click the photo to enlarge and see other photos.

Although the water in the upper reaches of the Old Crow River is clear enough that you can see fossils on the bottom, with very shallow water and a faster flow, along most of the course of the River through the Flats all the way to the canyon, there is very little current, and the water is muddy. The muddiness is partially due to the amount of material falling from the banks into the River.

"We could hear the sound of water from the melting ice lenses and the muck and other material which is continually falling into the river or onto an enormous pile of black muck, from which in turn much of it is rolling into the river. From high above, great masses of tundra matting and peat... are continually breaking loose and rolling down into the river, stopping, not at the edge as does the muck, but rolling clear into the middle of the river, at times even reaching the opposite shore" (Geist 1956?). On the river, sunken and partially sanded-in logs and other debris (festooned with green algae) which has rolled into the stream bed makes navigation difficult.

The bluffs along both the Old Crow and Porcupine Rivers afford the opportunity for unique studies of the faunal, geologic, and human history of this important unglaciated area. The bluffs are continually eroding, washing valuable specimens of fossil plants and animals, particularly Ice Age mammals, into the river . The slumping of materials from the banks along the Old Crow River not only has a significant impact on the quality of the water, on the wildlife that exists in the river, and on the naviability of the river, but also on the archaeological and palaeontological research that this area is famous for.

Figure 1.5c Click the photo to enlarge and see other photos.

The presence of permafrost and ground ice in the river banks results in particular active geomorphic processes, especially the rapid detachment of large areas of ground when material above the active permafrost layer detaches from the material still frozen. Another rapid process is the continual falling away of material from established edges due to thawing in areas of massive ground ice. These processes result in large areas of raw unvegetated surfaces where the process of plant succession, the gradual occupation by a distinctive order of species, can be observed.

As part of extensive studies of terrain sensitivity (the degree of reaction of the terrain to disturbance) in the northernYukon and Mackenzie area, Van Eyk and Zoltai (1975) classified the sensitivity of the Old Crow Basin south from what is now the southern part of Vuntut National Park to the Porcupine River. Terrain sensitivity is dependent on characteristics of the ecosystem such as: ice content (near surface or at depth), slope and material, and insulating cover. The glaciolacustrine deposits and organic peatlands of the Old Crow Flats were given a moderate to high sensitivity rating, based on the presence of fine-grained material with poor bearing capacity and ground ice, and the potential for slumping and thermokarst subsidence. (The uneven topography known as "thermokarst," which means literally "heat sink" or "heat depression", is created by the melting of the ground ice.

The recent river-deposited sediments (alluvium) of the Old Crow River valley and its tributaries were rated at low sensitivity for coarse sediments and moderate to high for fine sediments. Rivers and streams are subject to thermokarst subsidence, slumping, gully erosion, undercutting, and bank collapse.

An increase in riverbank erosion, slumping and sediment load in the river systems of the Old Crow Basin would be one result of projected climate warming (Environment Canada 2000).

Because of reduced ice thickness on all water bodies, larger spring runoff volumes, and slightly earlier spring peak flows (June rather than July) there could be significant changes to the hydrology of streams and rivers in Vuntut National Park.

The quality of salmon spawning grounds in the Old Crow Basin area would decline where there was increased stream flow erosion and sedimentation (Bryan et al. 1973). On the other hand, more upstream spawning areas may become available with more water flow, thereby softening some impacts of stream flows on fish populations (Environment Canada 2000). The projected increase in water volumes in streams and rivers could also lead to increased overwintering habitat for fish such as arctic grayling, longnose sucker and least cisco.

Erosion and its interaction with permafrost also has an important impact on archaeology. Morlan (1973) points out that archaeological excavations in late June and early July usually encounter permafrost at between 45 to 60 cm below the surface in grassy clearings, at 15 to 30 cm below the surface in poplar stands, and immediately at the surface under dense mats of sphagnum moss found in spruce forest. The presence of permafrost is a positive benefit in the preservation of organic materials, including bone, bark, and wood. The drawbacks are that testing is very difficult, excavations must be carried out in several trenches simultaneously, drainage quickly becomes a serious problem in deeper levels, and active and inactive frost cracks cause significant disturbance of the fine-sediment matrix of the sites (Morlan 1973).