Glossary Related to Sediment Transport - Sediment Transport in Irrigation Canals: A New Approach - page 271

APPENDIX E

Glossary Related to Sediment Transport

Abrasion Frictional erosion by material transported by wind and water.

Absolute pressure The pressure above absolute zero.

Absorbed water Water held mechanically in a soil and possessing the same

physical properties as ordinary water at the same temperature and
pressure.

Accretion Accumulation of sediment deposited by natural flow processes; increase

of channel bed elevation resulting from the accumulation of sediment
deposits.

Accuracy The degree of conformity of a measured or calculated value to its definition

or with respect to a standard reference.

Adequacy The ratio of the amount delivered to the amount required.

Adjustable flow Irrigation flow regulated at a specific discharge (flow rate).

Aggradation Build-up or rising of channel bed due to sediment deposition.

Alignment The course along which the centre line of a canal or drain is located.

Alluvial soil A soil formed from deposits by rivers and streams (alluvium).

Alternate depth In open channel flow, for a given flow rate and channel geometry, the

relationship between the specific energy and flow depth indicates that, for
a given specific energy, there is no real solution (i.e. no possible flow), one
solution (i.e. critical flow) or two solutions for the flow depth. In the latter
case, the two flow depths are called alternate depths. One corresponds to
a subcritical flow, the second to a supercritical flow.

Altitude Vertical height of a ground or water surface above a reference level (datum).

Amplitude Half of the peak-to-trough range (or height).

Analytical model System of mathematical equations that are the algebraic solutions of the

fundamental equations.

Angle of repose The maximum slope (measured from the horizon) at which soils and loose

materials on the banks of canals, rivers or embankments stay stable.

Armouring Progressive coarsening of the bed material resulting from the erosion of fine

particles. The remaining coarse material layer forms armour, protecting
further bed erosion.

Automatic control Adjustment of the controlling element accomplished by an arrangement

of equipment without attendance by an operator or continuous control of
equipment without intervention of an operator to predetermined
conditions.