Enhancements of small peaks using the moiré technique
Abstract A very simple technique is described for enhancing small peaks in 3D line drawings.
Modification of river tides by the discharge
The effect of an increased discharge on the tide progressing into a river is evaluated quantitatively by gaging the signal recorded at upstream stations against a reference station, during intervals of effectively constant discharge; this process is repeated for progressively larger values of the discharge. Upstream, the tidal range is reduced by an increased discharge; the time of arrival of low water is accelerated, while high water is retarded. The changes in range and in time may be represented by simple regression relations. Downstream an increased discharge causes a decrease in the effective friction during flood and an increase in it during ebb. Low water is retarded and high water is accelerated; some tidal components may actually be amplified over a segment of the river.
On tidal propagation in shallow rivers
A reexamination of the momentum balance in shallow rivers, with scaling appropriate to the Saint Lawrence and the Fraser, shows that frictional forces exceed accelerations over most of the tidal cycle. Consequently, tidal propagation in shallow rivers is more properly envisaged as a diffusion than as a wave propagation phenomenon. The long time lags associated with low waters, unexplainable in terms of a simple wave propagation model, are easily accounted for by an equally simple diffusive model.