Date of Award
Doctor of Philosophy (PhD)
Oceanography and Coastal Sciences
John W. Day, Jr
A study of materials fluxes across different scales of time and space was conducted in the Rhone Delta, France, to test the applicability of a conceptual model of deltaic ecosystem function in a scenario of accelerated sea-level rise to a mediterranean delta which has been heavily altered by human activities. Natural pulsing events such as tides, river floods and storms cause sediment surfaces to maintain elevation in the face of relative sea level rise through the process of soil formation. These pulses also enhance ecosystem function through habitat creation, food production, materials transformation, water quality and storm and flood protection. Human activities such as the construction of dams, levees and sea dikes have reduced the impacts of these natural pulsing events which operate on different scales of time and space. As a consequence, soil formation and accretion are lowered and ecosystem function is decreased. Despite human impacts the Rhone River is capable of large pulses of freshwater and sediments (average 4.8 x 1010 m3 yr -1 water, 8.2 million tons sediments yr-1) which cause net materials fluxes in deltaic wetlands in communication with the river. These wetlands import mostly inorganic suspended sediments which cause event-driven short-term sedimentation, a function of Rhone discharge and climatic conditions. Deposition of these sediments leads to vertical accretion in excess of relative sea-level rise. The wetlands also import dissolved inorganic nutrients which stimulate organic matter production, some of which is exported as chlorophyll to the adjacent estuary, showing important ecosystem functions. Wetlands in connection with the sea appear to be maintaining elevation, although no significant fluxes were measured within the study period. Most of the delta, however, is isolated from materials fluxes due to the presence of levees and dikes, which leads to low accretion and elevation change and a loss of ecosystem function. The results of this study show that significant pulsing energies and materials fluxes are available to the larger delta. It is recommended that holistic deltaic management take advantage of these energies in order to maintain and promote deltaic habitat and enhance ecosystem function in the face of accelerated sea-level rise.
Hensel, Philippe Francois, "Materials Fluxes Across Different Scales of Time and Space in the Rhone Delta, France." (1998). LSU Historical Dissertations and Theses. 6834.