CAESAR was originally developed by myself, as part of my PhD at the University of Leeds, U.K., under the supervision of Prof Mike Kirkby and Prof Mark Macklin. Since then it has grown somewhat, in both complexity and application. Now there are several people helping to improve CAESAR and involved in other similar research projects here at Aberystwyth, they are:

       
Gez Foster                           Ian Dennis (nice picture!)        Marco Van de-Weil

CAESAR was originally designed to investigate the relative roles of climate and land-cover on the Holocene evolution of river catchments in the UK. It is flexible, and relatively easy to apply to DEM's of any river catchment. As it was designed to operate over 10 to 10000 year time scales, CAESAR simulates every flood event - driven either by an input hydrograph or from a rainfall sequence - which drives an internal hydrological model. CAESAR was designed to pay close attention to fluvial processes - which it could be argued are most dominant at these time scales. Therefore, it operates with relatively small grid cells (they can range from 1-100m in size) and simulates the channel width with one or more cells. It allows divergent and convergent flow - so is ideal for simulating braided rivers and alluvial fans, and importantly carries out fluvial erosion and deposition over a range of grain sizes linked to a series of active layers. This can allow a stratigraphy to develop, as well as important fluvial effects such as bed armouring restricting sediment supply. 

This image is from the lower 10km of the River Swale (Yorkshire Dales, UK) between Richmond and Great Langton. The yellow and blue are flow depths 100 years apart. Yellow is the former, blue latter, and after 100 years of erosion and deposition, a channel avulsion can clearly be seen. Above the avulsion there are several areas where the channel has migrated laterally up to 150m.

Where CAESAR seems to differ from other models, is its scale of application. Many contemporary river management issues revolve around problems based on human time scales (1-100 years) and CAESAR can be used to see how rivers behave over these times. Furthermore, its concentration on fluvial processes again makes it useful for these applications. CAESAR has been applied to many catchments and river reaches e.g. Starbotton, the Swale, Ure, Ouse, Nidd, Vale of York, River Calder and the Rio Guadiamar to name but a few. It is far from perfect, but as a research tool I hope it is providing valuable insights into how river systems respond over these 'meso' scales. 

I am very interested in any fresh ideas for the application of CAESAR - and welcome people to download the code, have a play and see what they come up with! I really hope it can be of use to people for research into river system behavior and welcome any collaborative research opportunities.

For a more in-depth guide to the mechanics of the model and how it has been previously applied - I would like to refer you to some of the research papers I have published, that are listed in the CV/Publications section of these web pages. If you would like any re-prints please let me know and I can send some. 

TRACER
Tracer is now fully integrated within the CAESAR source code and quite simply allows the user to input a 'different sediment' at points through out the catchment and watch how the sediment moves, is stored and then re-mobilised.

The simplest analogy is to imagine the whole catchment has black sediment, and at certain sites you add white sand or sediment, then see how it moves - like a tracer (hence the name!).

There are many really good applications for this model. I have used it to simulate the fate of heavy metal contaminated sediments from a mine effected river catchment (see Geology paper in publications section, Coulthard and Macklin, 2003), but there are plenty of other issues to study. For example the transport of pathogens, and geomorphic studies - separate tributaries could be run with different 'colour' sediment and the relative mixing investigated.