Temporal changes in sediment distribution observed in MODIS images

Abstract

Changes in spatial distribution of suspended sediment discharged from large rivers could be the result of shortterm seasonal changes, inland environmental changes or re-suspension of bottom sediment by strong tidal currents. The time scales for these processes are different - the latter shorter than the former two. MODIS images collected between September 2004 and September 2005 are used to study the temporal variations in sediment distribution at the mouths of the Ayeyawady River and Gulf of Martaban, as well as, off the Mekong River Delta. Relatively cloudless images could be acquired almost daily during the dry season from December to February. The tidal influence on the sediment distribution can be clearly observed during this period - the largest areas of turbidity are observed during spring tides and the smallest areas during neap tides. These two regions are almost daily obscured by clouds from May to August. Nevertheless, seasonal variations due to the two monsoons can be discerned after eliminating tidal influence by selecting images acquired only during spring or only during neap tides. .