Tidal inlet short-term morphodynamics analysed trough the tidal prism - Longshore sediment transport ratio criterion

Longshore sediment transport and tidal prism are key factors in analyzing the stability and morphodynamics of a tidal inlet. Stablished by the Bruun theory, the ratio between the maximum spring tidal prism (P) and the annual total littoral drift (M-T) is a parameter widely used to diagnose the stability condition of tidal inlets and to validate inlet morphological modeling results. However, the P/M-T relationship is adequate for mid-term and long-term analysis only (i.e. weeks, months, years or decades). Depending on the wave climate, one may observe intense accretion in a tidal inlet in a time scale of hours to few days during storm events. No empirical criterion is yet known to be applicable for supporting analysis in such a short time scale. This work presents a modified approach of the traditional Bruun criterion, adapted for assessing short-term (i.e. hours or days) morphological evolution of tidal inlets. Instead of P and M-T, the method here addressed considers the ratio between the tidal prism (P-i) and the longshore transport volume (M-Ti) integrated both over the flood period of every tidal cycle. This methodology was applied in the analysis of storm and post-storm induced morphodynamic response of a projected tidal channel, proposed to improve water quality in the Araruama Lagoon, Rio de Janeiro, Brazil. Hydro-sedimentological numerical modeling was used to simulate a scenario which encompassed three cycles of storm induced accretion and post-storm induced inlet development. Correlation was noticed between the patterns of short-term morphodynamic response and the temporal variations of the instantaneous P-i/M-Ti ratio. This research also presents calculations on the longshore sediment transport rate during the four seasons for the studied region. (C) 2019 Elsevier B.V. All rights reserved.