Engineering Evaluation of Nearshore Bathymetric Change Using Remotely Sensed Data

As part of the US Army Corps of Engineers (USACE) mission, Coastal engineers and planners rely on data to make better informed decisions. This dissertation combines three separate studies that measure nearshore bathymetric change using large, regional datasets collected using remotely sensed techniques, namely airborne lidar surveys of sandy shorelines and single-beam and multi-beam hydrographic surveys of coastal navigation channels. The research in this dissertation examines the use of regional, recurring datasets to address the unique challenges in maintaining the United States’ complex water resources infrastructure.

The depth at which significant bathymetric change can be expected is an important morphological factor for science and engineering on sandy coastlines. Although most depth of closure studies have been conducted on a limited number of sites, the great quantity of airborne lidar bathymetry data collected over the past decade allows for a much wider study region. Here, we present depth of closure analysis over 600 km of sandy coastline using the Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX) dataset. Improved closure predictions resulted when both extreme waves (as represented by the 12 hour exceedance significant wave height over a given time interval), and more typical storm waves (as represented by the 99% significant wave height) were jointly considered. Results are presented for four closure criteria: root-mean-square depth changes = [20,30]cm, and relative depth changes = [0.02,0.04].

The second study used airborne lidar surveys to support a beach state classification model applied to wave-dominated sandy shorelines. Nearshore morphological features (e.g. number of sandbars and sandbar position from shore) were quantified. Several regions were studied to provide a detailed and comprehensive distribution of sandbar morphologies over large scales at wave-dominated, sandy shorelines of the United States. The configuration of the nearshore features were analyzed and trends were identified spatially as well as temporally in the analysis of a region with repeat surveys.

In the third study, hydrographic surveys are used to develop an improved metric of navigation channel availability that considers channel navigability, instead of by the shallowest observed depth in the channel. A new vessel routing algorithm was developed to provide a more viable alternative to the current method of determining channel availability, an alternative that allows the USACE to better quantify dredging needs, and allocate their limited dredging budget more appropriately. The components of the routing algorithm were reviewed in detail for three navigation channels. The case studies illustrated the ability of this automated vessel routing algorithm to contribute to an objective assessment of navigation channel availability that more closely aligns with real-world observations.

Together, these studies strive to improve upon metrics and methodologies that are used by engineers and planners for coastal project management.