project background

All rivers across the globe that exit to the ocean contain a zone, which can be 100s of kilometres long, which is transitional between river and tidal environments (termed here the Tidally-Influenced Fluvial Zone, or TIFZ). This zone is one of the most complex environments on the surface of the Earth because it is an area where both river flow and tidal currents are significant, and these competing forces vary daily, seasonally and annually.

These regions are important to humans and form some of the areas of highest population density: they are strategically important in the present day because these zones are at the interface of competing demands for shipping, aquaculture, land reclamation and nature conservation. In order to better maintain, manage and protect these fragile zones, we must understand how and why these regions change and what factors control such change.

Additionally, the sediments of ancient TIFZs may contain significant volumes of hydrocarbons which are increasingly the target for many energy companies. For example, the Athabasca oil sands form the largest petroleum deposit on Earth and these bitumen tars are locked up largely within ancient TIFZ sediments. We need to understand what controls the geometry and internal characteristics of these TIFZ sediments and thus plan efficient and maximal hydrocarbon extraction strategies.

All of these interests in both modern and ancient TIFZ environments depend on a detailed knowledge of the water flow structure in these areas, how such flows transport their sediment and critically how the form (or morphology) of these environments changes through time. This project uses integrated field and mathematical modelling techniques to achieve a step-change in our understanding of the TIFZ. We will use techniques that yield unrivalled high-resolution datasets of bathymetry, flow, sediment transport and sedimentary structure that will then be used to construct and validate new numerical models of the TIFZ. This will ultimately allow evaluation of key unknowns with respect to the TIFZ, such as how such environments evolve under changing scenarios of tidal and fluvial contributions associated with sea-level change, and whether it is possible to differentiate between 'fluvial' and 'tidally' influenced deposits. Such results will also help us recognise these changes within ancient sedimentary successions.

The TIFZ project is funded by the UK Research Council NERC and runs from 1 December 2010 to 30 November 2013. Fieldwork on the Columbia River Estuary (based at Astoria) has been completed in April 2011 (recce), June 2011, September 2011 and June 2012.