Chapter 1 - Introduction

Abstract

This chapter provides an introduction to sediments. The importance of sediments in hydraulic engineering and in the technical development of water resources is well known. In rivers, the total amount of sediment discharge is the most obvious and direct concern. Sediments also affect the roughness and the frictional resistance of natural waterways, thus raising the question of stage-discharge-sediment transport relationships. The stability of beds and banks against scouring and deposition is another important subject, particularly for manmade canals and waterways. The useful life of reservoirs depends on the sediment load of the contributing natural streams. The extent and frequency of maintenance of navigable waterways in estuaries are determined by the rates of deposition of sediments, particularly fine, by the discharging river or rivers into that specific estuary. Another serious problem in estuaries, bays, and lakes is sediment-induced pollution either by increasing the water turbidity or by depositing highly contaminated sediment on ecologically sensitive zones. There are cases where the environmental damage is so severe that the restoration of the original quality becomes either impossible or extremely difficult and expensive. For all these reasons, sedimentation is the subject of intensive fundamental, applied, and field research since the 19th century and many theories, empirical formulas, and semi-theoretical equations have been developed for the prediction of sediment transport rates and the control of channel stability.