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

Laura Lemke,Matthew S Janssen,Jon K Miller

doi:10.3390/jmse8110865

Laura Lemke, Matthew S Janssen + Show 1 more

Open Access

https://doi.org/10.3390/jmse8110865

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Abstract

A comprehensive case study of Keansburg Inlet (New Jersey, USA) is presented with the objective of evaluating inlet management alternatives and assessing the influence of an operational flood gate on channel shoaling. The goal of the research is determining the most effective strategy for minimizing the frequency of maintenance dredging. This study compares the effectiveness of (1) traditional structural solutions; (2) modified dredging templates; and (3) assesses the influence of the flood gate operations during conditions representative of a typical year. Alternative analysis is completed using a coupled hydrodynamic–wave model (Delft3D-Flexible Mesh (FM)) with Real Time Control to simulate morphological changes. The model was calibrated and evaluated using collected field data. Water levels are reproduced within 6% of the spring tide range with lag times less than 20 min. The model results and observations suggest sediment transport is dominated by wave action with pronounced variations in dominant wave direction. The results indicate that changes to the operational dredging, or what the authors have termed broadly as “adaptive dredging techniques”, appear to deliver the most promising improvement. Model results suggest that the current operational procedures of the flood gate do not significantly alter the channel infilling rates and patterns during typical (i.e., non-extreme event) conditions.

Highlights

Inlets are hydraulic connections between open bodies of water and comparatively protected waters, providing numerous benefits
The results indicate that changes to the operational dredging, or what the authors have termed broadly as “adaptive dredging techniques”, would likely reduce the frequency of dredging at Keansburg Inlet equal to than traditionally applied structural solutions
Model results suggest that the current operational procedures of the flood gate do not significantly alter the channel infilling rates or patterns during typical conditions

Summary

Introduction

Inlets are hydraulic connections between open bodies of water and comparatively protected waters, providing numerous benefits (e.g., navigation, water quality). Inlets have been broadly characterized as either primary or secondary inlets based on their formation [1] with the morphology of the inlet determined by the combined influence of tidal currents and waves. The inlets are characterized as either wave or tidally dominated [2,3]. Inlets are naturally maintained through the scouring of tidal currents counteracting the longshore sediment transport; the concept of scour velocity, weakly correlated to sediment diameter, was first introduced in the middle of the 20th century [4,5]. With high ecologic and socio-economic values, natural inlets are often maintained through anthropogenic activities, including maintenance dredging and the construction of jetties or breakwaters. It is notable that historical work has typically been focused on either relatively large, primary inlets (e.g., [8,9]) or focused in the immediate area of the inlet throat (e.g., [11])

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