Bio-physical characterization of sediment stability in mudflats using remote sensing: A laboratory experiment

摘要

Mudflats are important for coastal zone ecosystems by providing wildlife habitat and by acting as natural sea defenses that serve to dissipate tidal and wave energy. Geomorphological models of these intertidal flats and estuaries require site-specific bio-physicochemical sediment parameters as input. Hyperspectral remote sensing can be used as a tool providing synoptic maps of these properties. However, the interpretation of hyperspectral remotely sensed images over mudflats is only possible if the appropriate bio-geophysical or empirical models for information extraction are available. Therefore, the objective of this paper was to model the effects of varying sediment properties on the reflectance in laboratory conditions. The methodology consisted of (i) hyperspectral measurements of sediment mixtures with varying physical and biological characteristics in laboratory conditions, (ii) determination and quantification of specific absorption features and (iii) regression between the absorption features and physical parameters. In laboratory conditions, quantification of clay in dry sediment, moisture in unsaturated sediment and chlorophyll a in sediment mixtures was achieved with coefficients of determination (r~2) of 0.98, 0.90 and of 0.96 using the scaled band area of absorption features at 2204, 1450 and 673 nm, respectively. Additionally, the water absorption at 1190 nm was identified as suitable to predict moisture content in very wet sediment and preliminary results showed the potential of hyperspectral signals to assess the effect of bioturbation on sediment properties. Future work will consider the applicability of this methodology in field situations to relate bio-physical sediment parameters to the hyperspectral signal.