ABSTRACT
This chapter examines some of the modeling techniques used to estimate or describe the relationships among stream characteristics. The variability is controlled by the characteristics of the watersheds from which the flows originate. Rivers and streams range from small, ephemeral, or intermittent streams that flow only in response to rainfall, to rivers such as the Mississippi-Missouri system in the US The degree of resolution required in a flow model depends primarily on the known or expected homogeneity or uniformity of hydraulic and water quality characteristics. An alternative approach characterizes cross-sections as a function of depth using mathematical relationships such as power formulas or polynomial equations. Comparisons of predicted and measured hydraulic characteristics demonstrate the adequacy of boundary condition data and channel geometry characterization and aid in the selection of bottom roughness coefficients. Dispersion coefficients can be estimated using one of a variety of empirical or semi-empirical equations that generally relate the dispersion rate to shear stress.
