Cancun beach rehabilitation project

Abstract

The major part of the ongoing growth of the worlds population takes place in coastal zones, making that coasts are more and more intensively used. However, coasts are dynamic systems characterized by variability in shoreline position and profile shape, which sometimes conflicts with human interests as is the case at Cancach in Mexico. In addition to hard coastal structures, beach nourishment is often used as a measure against erosion. After placement, the fill sediments are distributed across and along the shore by the action of waves and currents. This morphological behaviour consists of longshore spreading-out of the fill sediments and of cross-shore equilibration, i.e. the transformation of the construction profile to the dynamic equilibrium profile. However, this morphological behaviour is difficult to predict, complicating beach nourishment assessment and inducing the need to develop better modelling and design methods. Various modelling and design methods for beach nourishment are available, covering different aspects of the morphological behaviour. In this thesis the cross-shore modelling of the beach fill equilibration has been considered. The planned beach fill at Cancach (Mexico) has been used as a case study. Three possible borrow areas with varying sediment properties have been considered. Various design methods based on equilibrium models have been compared with process-based numerical modelling with the software package Unibest-TC (WL | Delft Hydraulics), leading to conclusions regarding the suitability of these design methods for beach fill equilibration. Furthermore, recommendations regarding the time scale of the beach fill equilibration and the final profile shape of the Cancach fill are made.