Emergence and drowning of fluviodeltaic systems during steady rise of sea level: Implication from geometrical modeling and tank experiments

Abstract

Drowning of coastal environments is believed to be a primary consequence of sea level rise predominating over sediment supply. Casting doubt on this conventional notion, our geometrical model, along with supportive physical experiments, suggests that where hinterland slope is steeper than delta’s foreset slope, (1) complete drowning of a fluvial delta is possible even with constant rise of relative sea level (rate r_slr) and constant sediment supply (rate q_S) (autodrowning), (2) there exists a critical magnitude of initial water depth (H_crt) that does not allow an initially drowned depositional system to become emerged or develop an alluvial realm, and (3) where initial water depth is smaller than H_crt, the initially drowned depositional system inevitably changes into a deltaic one (autoemergence). There does not exist a balanced state between q_S (›0) and r_slr (›0) with which a depositional system can hold deltaic sedimentation and avoids autodrowning and/or preceding autoemergence. The function of q_S and r_slr is simply to determine how fast these autogenic processes are attained and how large H_crt is.