HYDRAULIC SURVEY AND MODEL INVESTIGATION OF THE INNER RANA FJORD

Abstract

The characteristic feature of the water masses in a fjord is their stratification. This stratification and its annual cycle are explained in terms of the physiography of the fjord regions. The glacial origin of these regions is outlined in order to expose the sediment sources and the present sediment regime. A case study of a fjord in Northern Norway is reported. The results of a field survey comprising measurements of tidal and river flows are given. The measurements revealed that the tidal flow had a steady component giving a horizontal circulation in the fjord, in addition to the vertical circulation associated with the diffusion of salt water upwards into the surface layer. The reduced scale model of the lower river and the Inner Fjord was built to avoid adverse affects of a constriction of the river mouth. The model also showed that a small jetty would turn the turbid surface jet away from the incoming tidal current towards the outbound current caused by the horizontal circulation, thereby relieving the harbour area of some of its present sediment supply.