The processes of erosion, transport, and deposition of sediment particles introduced in Chapter 1 relate to the interaction between solid particles and the surrounding fluid. This chapter describes physical properties of water and solid particles in terms of dimensions and units (Section 2.1), physical properties of water (Section 2.2) and of sediment (Section 2.3). The method of dimensional analysis (Section 2.4) is then applied to representative erosion and sedimentation problems.

Dimensions and units

The physical properties of fluids and solids are usually expressed in terms of the following fundamental dimensions: mass (M), length (L), time (T), and temperature (T°). The fundamental dimensions are measurable parameters which can be quantified in fundamental units.

In the SI system of units, the basic units of mass, length, time, and temperature are the kilogram (kg), the meter (m), the second (s), and the degree Kelvin (°K), respectively. Alternatively, the Celsius scale (°C) is commonly preferred with the freezing point of water at 0°C, and the boiling point at 100°C.

A newton (N) is defined as the force required to accelerate one kilogram at one meter per second squared. Knowing that the acceleration due to gravity at the Earth's surface g is 9.81 m/s2, the weight of a kilogram is obtained from Newton's second law: F = mass × g = 1 kg × 9.81 m/s2 = 9.81N. The unit of work (or energy) is the joule (J) which equals the product of one newton times one meter.