Synonyms for Alluvion (same or very similar meaning)
WordNet sense 1 (the rising of a body of water and its overflowing onto normally dry land):
deluge, flood, inundationWordNet sense 2 (clay or silt or gravel carried by rushing streams and deposited where the stream slows down):
alluvium, alluvial sediment, alluvial depositFrom the ODE community, based on WordNetadd/edit