The development of a regime model for prediction of the long-term effects of civil engineering activities on estuaries

The prediction of impacts of civil engineering activities on estuaries over the long term has become an increasingly important issue, owing to a varie ty of commercial, social and environmental reasons. Estuaries are highly co mplex systems involving a large number of variables and processes, many of which cannot be precisely described, owing to lack of adequate theory. This gives rise to problems in the formulation of detailed numerical models and as a result such models have proved to have severe limitations in the long -term prediction of engineering activities. A functional rather than a deterministic approach is therefore proposed, wi th emphasis being given to the way in which bulk parameters involving sedim ent transport and river and tidal discharges can be related to estuary geom etry. From correlation analyses on a range of morphological relationships, it is shown that the relationship between peak tidal discharge and estuary cross-section at peak discharge, gives the best correlation. A hybrid model is proposed consisting of a 1-D flow model to describe the e stuary hydrodynamics coupled with a morphological algorithm to model sedime nt movement. A description is given of the application of the model to a tidal barrage a nd a training-wall scheme. (C) 2000 Elsevier Science Ltd. All rights reserv ed.