Interest in tidal freshwater river (tidal river) ecosystems is rapidly growing in fluvial, estuarine, and wetland science.  The acceleration of interest in tidal rivers is driven by recently observed ecological and geomorphic changes occurring in these ecosystems around the world, as well as new information highlighting the influence of tidal rivers on the flux of water, sediment, and elements from land to the coastal ocean.  Changes in the morphology, vegetation, and biogeochemistry of tidal rivers are occurring rapidly in some rivers but slower in others. These dynamics are driven in part by sea level rise, although the specific mechanisms by which tides affect freshwater river morphology and biogeochemistry are poorly understood.  Furthermore, it is unclear how changes in watershed inputs of water, nutrients, and sediment interact with the changes in sea level to influence tidal river ecosystems.  This transitional system has historically had less research than the end-member fluvial and estuarine systems, and this knowledge gap poses challenges to applied sciences related to nutrient, sediment, and conservation management. Prediction of future changes in structure and function of these river ecosystems due to sea level rise, as well as understanding contemporary patterns and processes in tidal rivers, requires knowledge of the feedbacks that occur between river hydrology, geomorphology, and biota.

Advancing knowledge of tidal river ecosystems requires multidisciplinary efforts and collaboration among wetland ecologists, biogeochemists, and both fluvial and estuarine geomorphologists and hydrologists. This Chapman Conference is designed to unify discussions on tidal freshwater river ecosystems by focusing on the feedbacks that link the disciplines of fluvial, estuarine, and wetland science.  Using this feedback framework for synthesis, the following questions will be addressed:

  1. * How are channel cross-section and planform morphology affected by tidally-influenced river flow over time, and how is river flow subsequently affected by channel morphology?
  2. * What feedbacks occur between riparian biota, tidal river hydrology, and channel/floodplain geomorphology, and how do these feedbacks change over time?
  3. * How is biogeochemical cycling in rivers affected by the geomorphic and biogeochemical feedbacks described above, and what is the resultant effect on elemental fluxes from watersheds to estuaries?
  4. * How sensitive are eco-geomorphic feedbacks in tidal rivers to the rate of sea level rise as well as changes in watershed inputs, and can they result in alternative, yet persistent patterns in tidal river morphology and ecological functioning?