The chemistry, mineralogy, and rates of transport of sediments in the ...

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which is positively related to watershed area . This finding supports the
largely inferred importance of the relative size of Qa and Ad in proportion
to a given terrain disturbance (Brunskill et al ., 1973) . Since over
80 of the variability in transport rates of SS a , PCa , PNa and PPa was
explained by the-magnitude of the land drainage area (Ad), then a given
area of land disturbance in a small watershed is likely to have much greater
effects on sediment and particulate matter supply rates to streams than
would the same disturbance in a large watershed . In fact, it is likely
that streams with low values of b (see Table 2) will not be able to carry
added sediments and nutrients from land disturbance, and the added sediments
will accumulate in the stream bed . In_ Temperate Zones of North America,
this Ad-SSW relationship is Just the opposite ; i .e . erosion rates usually
decrease with increasing Ad (Brune, 1948 ; Langbein and Schumm, 1958 ; Schumm,
1963) . It seems likely that the absence of small mountain streams (such
as Twisty Creek (Jasper, 1974)) in our data set has caused an over-emphasis
on the importance of watershed area in controlling erosion rates . If we
had a more representative suite of watersheds, we feel that Ad would greatly
decrease in importance, and relief, vegetation, and runoff coefficients
would be score important .' Our analyses (Table 13) do indicate the importance
of relief and forest cover in controlling transport (erosion) rates of particulate
material . These data support the work of many terrain studies, which
also identify these parameters (GE and F) as being important in maintaining
terrain stability (for example, Zoltai and Pettapiece, 1973 ; Crampton, 1973 ;
Strang, 1973 ; Hughes et al ., - 1973) . Deforestation in watersheds of moderate
to great relief (i .e . having great stream energy to carry sediments, high
values of b and moderate to high values of a in Table 2) would likely result
in measureable increases in the annual transport of most elements in stream
particulate matter (for an example in the Temperate Zone, see Hansmann and
Phinney, 1972) . In low relief, low energy streams (i .e ., low values of
and high-values of a, see Table 2), deforestation and land disturbance will
likely result in increased . rates of supply of sediment to the stream, but
the stream will' be less able to carry this added'sediment .
Bedload
Our limited data for Jean-Marie Creek indicate that in small streams
(A