The Impact of Storm-Induced Breaches on Barrier Coast Systems Subject to Climate Change—A Stochastic Modelling Study

Storms can have devastating impacts on barrier coasts causing coastal erosion, partial inundation, and possibly the breaching of barrier islands. The breaching of barrier islands provides a mechanism for the creation of new tidal inlets that connect the backbarrier basin (or lagoon) and the outer sea. As a new tidal inlet affects both the basin and the hydrodynamics of existing inlets, it is important to understand why an initial breach either closes or may evolve into a new tidal inlet. To this end, we performed a Monte Carlo analysis using an idealized model capable of simulating the long-term morphological evolution of multiple tidal inlets connected to a single backbarrier basin. To do so required the creation of a stochastic shell, as a new element around this existing barrier coast model. Our results demonstrate that barrier coast systems tend towards an equilibrium value for the number of inlets per kilometer of barrier coast and total inlet cross section. This even holds with the continuous stochastic forcing of storm-induced breaches. This finding implies that if a new breach opens in a coast that is already in equilibrium, existing inlets will shrink and may close if the new breach remains open. Furthermore, we find that climate-driven changes in storm frequency will modify the timescales in which barrier coasts reach their equilibrium state. Finally, we find that the distance between a new breach and its nearest neighbor is more important for its survival than the size of the breach or the degree of saturation of the barrier coast.