Deterministic Catchment Modelling

Abstract

The modelling of catchment behaviour will be taken in the quantitative sense either of reconstructing past rainfall-to-runoff behaviour or of forecasting future runoff behaviour from design rainfalls (or from currently occurring rainfalls). The topic has been studied in a number of ways over many decades. The early developments often used physical models (sand tanks, scale hydraulic models etc.), or analogue models (electrical analogues, viscous flow analogues etc.). Such models were based on mathematical descriptions of the relevant catchment processes, but used physical realisations. Alongside those approaches was a variety of empirical mathematical models, for example the Rational (Lloyd-Davies) formula for flood peak: Q_p = C i A involving rainfall rate, i, and catchment area, A, with a coefficient, C. More recent developments have made use of the vast power of computers to construct and use far more realistic mathematical models of the physics of catchment processes, an effort broadly encompassed by the description “deterministic modelling”. Later still, a powerful array of statistical modelling techniques has become available. There is thus a wide range of tools in the river flow forecaster’s tool kit. This section of the book deals with deterministic catchment modelling.