Df. Raikow et al., DEBRIS DAM DYNAMICS AND COARSE PARTICULATE ORGANIC-MATTER RETENTION IN AN APPALACHIAN MOUNTAIN STREAM, Journal of the North American Benthological Society, 14(4), 1995, pp. 535-546
Debris dam structure and retention of coarse particulate organic matte
r were examined during a 17-mo period in Powdermill Run, a 3rd-order A
ppalachian Mountain stream. Through the use of detailed feature maps,
changes in debris dam morphology were recorded, including the complete
''life-cycle'' (i.e., initial formation to destruction) of a dam. Str
eam sections in which dams were naturally destroyed became markedly le
ss retentive. Leaves were used as tracers in retention experiments tha
t varied in duration from 3 h to 4 wk. Results implied that migration
over time occurred by a simple mechanism of leaves falling off rocks a
nd settling into debris dams. A series of releases over 12 d showed in
creasing retentiveness as discharge decreased: Seasonal differences in
retention potential were evaluated using 3-h releases conducted durin
g winter, summer, and autumn Summer was the most retentive season due
to base-flow conditions. Debris dams were most retentive in autumn,les
s so in winter, and least retentive in summer. Cobbles showed the oppo
site pattern Leaf retention ranged from 1.8 to 23.2% retained/m (-k: 0
.02 to 0.26), depending on season A significant negative relationship
was found between mean depth and % retained/m, but the relationship of
% retained/m to discharge was not significant. A consideration of sea
son is necessary when comparing retentive abilities between streams.