DEVELOPMENTS IN MONITORING AND MODELING SMALL-SCALE RIVER BED TOPOGRAPHY

Recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography, flow hydraulic s and sediment transport. Although understanding of the behaviour of d ynamic river channels has been increased markedly through detailed wit hin-channel process studies, less attention has been given to the accu rate monitoring and terrain modelling of river channel form using thre e-dimensional measurements. However, such information is useful in two distinct senses. Firstly, it is one of the necessary boundary conditi ons for a physically based, deterministic modelling approach in which three-dimensional topography and river discharge drive within-channel flow hydraulics and ultimately spatial patterns of erosion and deposit ion and therefore channel change. Secondly, research has shown that an alternative means of estimating the medium-term bedload transport rat e can be based upon monitoring spatial patterns of erosion and deposit ion within the river channel. This paper presents a detailed assessmen t of the distributed monitoring and terrain modelling of river bed top ography using a technique that combines rigorous analytical photogramm etry with rapid ground survey. The availability of increasingly sophis ticated terrain modelling packages developed for civil engineering app lication allows the representation of topographic information as a lan dform surface. Intercomparison of landform surfaces allows visualizati on and quantification of spatial patterns of erosion and deposition. A detailed assessment is undertaken of the quality of the morphological information acquired. This allow some general comments to be made con cerning the use of more traditional methods to monitor and represent s mall-scale river channel morphology.