Downstream effects of dams on alluvial rivers

Journal Article · Tue Jan 01 04:00:00 EST 1985 · U.S. Geol. Surv., Prof. Pap.; (United States)

OSTI ID:6406797

Williams, G P; Wolman, M G

This study describes changes in mean channel-bed elevation, channel width, bed-material sizes, vegetation, water discharges, and sediment loads downstream from 21 dams constructed on alluvial rivers. Most of the studied channels are in the semiarid western US. Flood peaks generally were decreased by the dams, but in other respects the post-dam water-discharge characteristics varied from river to river. Sediment concentrations and suspended loads were decreased markedly for hundreds of kilometers downstream from dams; post-dam annual sediment loads on some rivers did not equal pre-dam loads anywhere downstream from a dam. Bed degradation varied from negligible to about 7.5 meters in the 287 cross sections studied. In general, most degradation occurred during the first decade or two after dam closure. Bed material initially coarsened as degradation proceeded, but this pattern may change during later years. Channel width can increase, decrease, or remain constant in the reach downstream from a dam. Despite major variation, changes at a cross section in stream bed elevation and in channel width with time often can be described by simple hyperbolic equations. Equation coefficients need to be determined empirically. Riparian vegetation commonly increased in the reach downstream from the dams, probably because of the decrease in peak flows. 120 references, 49 figures, 14 tables.

• OSTI ID: 6406797
• Journal Information: U.S. Geol. Surv., Prof. Pap.; (United States), Journal Name: U.S. Geol. Surv., Prof. Pap.; (United States) Vol. 1286; ISSN XGPPA
• Country of Publication: United States
• Language: English

Related Subjects

13 HYDRO ENERGY
130600* -- Hydro Energy-- Environmental Aspects
DAMS
DATA
ENVIRONMENTAL EFFECTS
EQUILIBRIUM
EXPERIMENTAL DATA
HYDROLOGY
INFORMATION
NUMERICAL DATA
RIVERS
SEDIMENTS
STREAMS
SURFACE WATERS