Environmental Engineering Reference
In-Depth Information
Figure 3.52.
Cross section through the site for Kosciusko Dam.
Figure 3.53.
Log of shaft, Kosciusko Dam site.
vast amounts of gravels and sands in braided (multiple-channel) rivers usually extending
tens of kilometres downstream, often across broad outwash plains (
Figure 3.54
). Grain
sizes range from gravel-dominated near the glaciers to sands and silts further down-
stream. In some places lakes are formed, in which laminated silts and clays are deposited.
Deposition, eroding and reworking of the braided river deposits occurs cyclically in
phase with glacial advances and retreats, resulting in terraces at various levels across the
river valleys and outwash plains. The streams eventually flow into lakes or the sea.
Exposed areas of silt and fine sand are eroded by wind and redeposited as loess on the
surrounding country.
Miall (1985) describes sedimentological aspects of the braided stream deposits.
The sands and gravels are usually clean with well-rounded particles and often provide
excellent sources of materials for embankments and for concrete aggregate.
