HR: 13:55h
AN: NG12A-02 INVITED     [PDF]
TI: Comparative geomorphologic organization of river and tidal networks
AU: * Rinaldo, A
EM: rinaldo@idra.unipd.it
AF: International Centre for Hydrology "Dino Tonini" University of Padua, via Loredan 20, Padova, I-35122 Italy
AU: Lanzoni, S
EM: lanzo@idra.unipd.it
AF: International Centre for Hydrology "Dino Tonini" University of Padua, via Loredan 20, Padova, I-35122 Italy
AU: Marani, M
EM: marani@idra.unipd.it
AF: International Centre for Hydrology "Dino Tonini" University of Padua, via Loredan 20, Padova, I-35122 Italy
AB: We address a comparative analysis of certain features observed in river and tidal networks, chiefly to explore the dynamic origin of the extraordinary diversity and yet the deep symmetry that one observes in such particular landforms. It seems of particular interest to compare network structures and a few geomophic features because of the vast diversity (and the relatively high degree of understanding) of the morphologic, hydrologic and ecobiologic processes at work in such eartscapes. River networks are indeed a paradigm of scale-invariant landforms from open, dissipative systems with many degrees of freedom quite ubiquitous in nature, and are described by a noteworthy body of observational and theoretical work, which is briefly reviewed in this context. Tidal networks bear mixed signatures of dynamic processes acting at different scales and are vastly more susceptible to environmental factors. Salt marshes in tidal environments, home to such networks, are thus characterised by complex patterns both in their geomorphic and ecological features. Such patterns arise through the elaboration of a network structure driven by the tidal forcing and through the interaction between hydrodynamical, geophysical and ecological components (e.g. microphytobenthos and vegetation). Therefore similarities and departures from observed features in fluvial and tidal environments are deemed of interest, in particular because we find that some purported similarities are artefacts of the measuring tools. This is not uncommon in networks studies. We show that remote sensing (and ancillary data) may be used to monitor vegetation and morphological changes of tidal landforms at different spatial and temporal scales. We use accurately georeferenced field observations coupled to aerial (ROSIS, MIVIS, CASI, and LiDar) and satellite (IKONOS and QuickBird) remotely sensed data. We then analyze the spatial distribution and variability of some vegetation indicators (e.g. NDVI) and the typical patterns of vegetation clusters obtained through classification and unmixing techniques. Finally, we study the relationships between vegetation species and organisation and various topographic/geomorphic parameters (e.g. soil elevation, proximity to the channel network, etc.). The remotely sensed data are radiometrically calibrated, atmospherically corrected and accurately georeferenced to allow the comparison with ground truth observations. Thus we claim that observations in both the river basin and the tidal earthscapes are equally accurate across their range of scales. Classification and unmixing techniques are then used to derive the spatial distribution of salt marsh vegetation species, which are also characterised through the use of vegetation indexes, allowing an objective and quantitative analysis of vegetation patterns. The set of observations available are further used, together with mathematical models, to describe channel meandering characteristics, drainage densities and branching properties yielding an accurate and spatially distributed description of the tidal network. Our observations and the proposed geometrical descriptors also allow a comparative morphological characterization of tidal and fluvial meanders, with unexpected similarities and sharp differences.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1824 Geomorphology (1625)
DE: 1848 Networks
DE: 1851 Plant ecology
DE: 1890 Wetlands
SC: Nonlinear Geophysics [NG]
MN: 2003 Fall Meeting