Assessment of Dredging Scenarios for a Tidal Inlet in a High-Energy Coast

Abstract

The high energetic wave climate of the North Atlantic Ocean causes important morphological changes at Figueira da Foz coastal system (W Portugal), which is comprised of sandy beaches and the Mondego estuary-inlet. The submerged sandbar at the inlet mouth is highly dynamic inducing short waves shoaling and breaking processes that can entail navigation problems towards the local harbor. Therefore, coastal dredging operations are performed to guarantee safe navigation. Nevertheless, these operations have a limited temporal effectiveness and require a high annual budget to be accomplished. The goal of this research is to seek long-life dredging alternatives using modeling tools (i.e., Delft3D model suite). Delft3D model is used to simulate the morphological evolution of five dredging scenarios during a three-month winter period under three wave climate scenarios. The bed level differences at the dredged area and at the inlet mouth for each scenario are analyzed in comparison with numerical solutions obtained in a reference scenario (i.e., no-dredging). Results highlight morphological changes at the dredged inlet and surrounding areas and their effectiveness in extending the operational lifetime of inlet dredged operations on dredging configuration and wave climate conditions. These findings are the basis for selecting the most suitable dredging scenario to this coastal region under current wave climate conditions.

An Integrated Approach to Study the Morphodynamics of the Lignano Tidal Inlet

“…Since the aim of the present study is to examine the narrowing process of the Lignano tidal inlet from both a theoretical and a quantitative point of view, the average year has been chosen as the reference morphological period to be analyzed. This time frame is therefore very different from that of a single storm or at most a few months [8] and it required a preliminary analysis to reduce and combine the events [27].…”

“…Tidal inlets act primarily as hydraulic regulators of water exchange between the sea and the back-barrier basin; they also function as both source and sinks of sediment in this manner governing the morphological, ecological and environmental balance of the adjacent coastal system [8]. Moreover, in many cases, they represent preferential waterways towards harbor sites located at the back-barrier basin, increasing the socio-economical value of these natural connections [9].…”

“…The selection of the representative conditions and their sequencing depends on which phenomena prevail; since waves and tides evolve over different time scales, the task of recognizing the correct reduced input set is not an easy challenge. For this reason, in several applications the tide and the wave motion have been simulated separately [25][26][27][28], refer to simplified imposed wave conditions [8,15,29] or short recorded time series [30].…”

Mitigation of Channel Shoaling at a Sheltered Inlet Subject to Flood Gate Operations

“…This study utilized the modeling package Delft3D-Flexible Mesh (FM) [45], which has been routinely used to simulate the hydrodynamics and morphodynamics of complex inlet systems [12,13,16,17]. A depth-averaged (2DH) hydrodynamic module was coupled (two-way) with a wave module, based on SWAN [46,47], and a sediment transport module.…”

“…While these simplified methods are convenient and provide some insight to the processes governing inlet stability, quantitative comparison of proposed anthropogenic activities (e.g., construction of erosion control structures or dredging operations) using these approaches is often not possible. Therefore, process-based models are often used to investigate both the processes driving sedimentation [12][13][14] and the potential impact of structural and non-structural inlet management alternatives [15][16][17][18][19]. Often, these studies have focused on larger open coast inlets.…”