Living Shorelines: Site Assessment and Engineering Design Fundamentals

BasePDH  |  Course No. 007  |  2 PDH

Source: NJDEP Living Shorelines Guidance

Publisher: New Jersey Department of Environmental Protection (NJDEP), Division of Land Resource Protection
Supporting references: USACE Coastal Risk Reduction and Resilience (2013), National Research Council — Mitigating Shore Erosion along Sheltered Coasts (2007), NOAA Coastal Change Analysis Program (C-CAP), NOAA tidal gauge records

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Introduction

Over the past century intensive development in the coastal zone has resulted in the proliferation of traditional "hard" shoreline stabilization measures such as bulkheads, seawalls, and revetments. While these approaches have proven to be successful at stabilizing shorelines when designed and constructed properly, they can also have a number of less desirable impacts on adjacent shorelines and critical intertidal and nearshore habitats. More recently, a variety of new shoreline stabilization approaches have been developed that attempt to incorporate natural features and reduce erosion by mimicking features of the natural environment. These approaches have come to be known by a variety of names including "living shorelines", "green shores", "ecologically enhanced shorelines", and "natural and nature-based features (NNBF)", among others.

Originally developed in the Chesapeake Bay nearly two decades ago, the "living shorelines" approach has gradually gained momentum and has spread nationwide. In 2007, the National Academies Press released the report, Mitigating Shore Erosion along Sheltered Coasts (National Research Council, 2007), which advocated the development of a new management framework within which decision makers would be encouraged to consider the full spectrum of options available. More recently, the US Army Corps of Engineers (USACE) released a report on coastal risk reduction and resilience which advocates for an integrated approach to risk reduction that draws from the full array of measures available (US Army Corps of Engineers, 2013). Both documents strongly encourage greater consideration of projects such as living shorelines projects which have the dual benefit of shoreline stabilization and habitat creation.

While this technique was originally applied only to low-profile stone or natural breakwaters known as marsh sills, the term "living shoreline" has evolved to take on a broader meaning which encompasses a wide variety of projects that incorporate ecological principles into engineering design. New Jersey's Coastal Zone Management Rules define a living shoreline as a "shoreline management practice that addresses the loss of vegetated shorelines, beaches, and habitat in the littoral zone by providing for the protection, restoration or enhancement of these habitats" (N.J.A.C. 7:7-1.5). It is important to note that the primary function of a living shoreline is the stabilization of the shoreline edge; while flood mitigation is needed in many coastal and riverine areas, a living shoreline is often not the most appropriate tool for addressing flooding issues.

The objective of this course is to provide practicing engineers with a thorough grounding in the engineering components involved in the design of living shorelines projects, consistent with the most up-to-date research. While the document is intended to provide the framework for the engineering design of living shorelines projects, the nature of these projects is such that diversity and innovation should be encouraged rather than discouraged. Innovation is identified in both the Waterfront Alliance's Waterfront Edge Design Guidelines (WEDG) (Waterfront Alliance, 2018) and the USACE's International Guidelines on the use of Natural and Nature-based Features for Flood Risk Management (IGNNBF) (Bridges, et al. 2021) as critical to the advancement of nature-based shoreline design.

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Purpose

Many documents have been developed with the objective of educating policymakers, regulators, and property owners on the engineering and ecological aspects of living shorelines. The guidance presented here was developed specifically for practicing Professional Engineers working in coastal and shoreline design, to ensure that living shorelines projects are designed, permitted, and constructed using the best available information. The guidance is being developed at a critical time when living shorelines projects are becoming an increasingly popular alternative for stabilizing shorelines and restoring natural habitat.

In July 2013, the State of New Jersey officially adopted Coastal General Permit 24 (N.J.A.C. 7:7-6.24) — commonly referred to as the Living Shorelines General Permit — which was written to encourage "habitat creation, restoration, enhancement, and living shoreline activities" and to remove some of the regulatory impediments for these projects. The guidance provided in this document is intended to be consistent with the statutes and limitations outlined in Coastal General Permit 24.

The guidelines that have been developed are intended to:

• identify the parameters critical to the success of living shorelines projects
• outline the level of analysis required to understand those parameters
• provide guidance on how to incorporate them into a successful project design

The objective is to reduce the number of poorly engineered or improperly designed structures, while at the same time recognizing that some living shorelines projects do not need the same level of detailed engineering analysis as traditional approaches. Moreover, the intent is to provide a document that can serve as a common starting point for both project designers and regulators, such that the framework, design process, and expectations are more clearly understood by both parties at the outset of a project. Due to the underdeveloped state of knowledge about living shorelines projects in the Northeast (north of Maryland), it is expected that these guidelines will continue to evolve as more information becomes available. It is also expected that from time-to-time projects may be constructed as functional experiments and that there may be reasons to deviate from the proposed guidelines to achieve a specific research objective.