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rainfall contributes a larger proportion of total precipitation. In fact, runoff consumes the
majority of total precipitation, with runoff ratios ( R / P ) as high as 0.7-0.8 for most basins
excluding wetlands. A problem with these sorts of analyses is that relatively little is known
about the rate of snow sublimation.
10.2.4. Sediment Flow, Surface Transport, and Denudation
Sediment movement in periglacial environments occurs through a combination of solu-
tion, suspension, and bedload transport. There are numerous sources of sediment for such
transport. Weathering (see Chapter 4) produces fi ne rock particles, and mass-wasting
processes (see Chapter 9) move material towards the stream channels. Moreover, many
areas possess an abundance of loose and unconsolidated sediment inherited from previous
glacial periods.
From a geomorphic point of view, it is of interest to know when, and under what condi-
tions, the majority of sediment is transported. Unfortunately, few long-term studies
monitor both stream discharge and sediment load. Table 10.4 summarizes some of the
available data for Arctic Canada. Bedload transport is especially diffi cult to determine.
One solution used (Church, 1972) is to derive solution and suspended-sediment values
(see Table 10.4) by traditional fi eld methods but to estimate bedload as values of “potential
sediment transport” at full supply. Accordingly, calculated values may be overestimates.
Moreover, because the Baffi n Island study (see Table 10.4) was undertaken in a proglacial
environment where current sediment yield is derived from unconsolidated glacial sedi-
ments, sediment yield bears no relationship to present rates of sediment production
(Church, 1972, p. 63). In spite of this caution, the limited data available suggest that a
dominance of bedload sediment transport is probably characteristic of many periglacial
rivers, even in areas unaffected by recent glaciation. For example, over 80% of the sedi-
ment transfer in the Colville River of northern Alaska was of either a bedload or sus-
pended nature (Arnborg et al., 1967), and, in a small permafrost drainage basin in northern
Yukon Territory, a bedload transport approximately three times that of suspended load
transport (444 t/km 2 versus 153 t/km 2 ) was reported for a 12-day period during peak dis-
charge (Priesnitz and Schunke, 2002). Essentially similar conclusions are reached, by
default, in several ongoing weathering and sediment-budget studies in northern Swedish
Lapland (Beyrich et al., 2003, 2004a, b; Darmody et al., 2001; Thorn et al., 2001). Although
chemical weathering and denudation is certainly important locally, as at Kärkevagge
(Rapp, 1960a; see Chapter 4), more typical results from elsewhere in that region indicate
that solute concentrations and chemical denudation amounts are generally low (Beyrich
et al., 2003, p. 394). Moreover, Table 10.4 indicates that, for most catchments, suspended-
sediment yields are generally higher than solute yields.
Further insight into the signifi cance of fl uvial processes in fashioning the periglacial
landscape is provided by data in Table 10.5. A wide range of sediment yields are found in
arctic regions. For example, when compared with a suggested North American mean yield
of 130 tones km −2 year −1 (Gregory and Walling, 1973), these data sets suggest that perigla-
cial yields are not signifi cantly different from those of other environments (Table 10.5A).
Furthermore, much solute transport is of the same order of magnitude as suspended sedi-
ment transport (Table 10.5B), and other data suggest that the dissolved organic carbon
transport for major northern rivers is similar to that of other major river systems of the
world (Table 10.5C).
Computations involving the total amount of material transported from the Baffi n
Island watersheds (see Table 10.4) indicate average ground surface lowering of the order
of 200-450 mm/1000 years. However, as noted earlier, it is probable that normal sediment
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