Gary Griggs

Recent Papers

Gary-Lida-Kiki.pdf

Coastline and Beaches of California: Past, Present, and Future

California’s 1,100-mile coastline is one of the most geologically diverse and dynamic in the United States. Shaped over millions of years by tectonic forces, waves, and changing sea levels, it has also been extensively altered by human development. Dams, debris basins, harbors, and other structures have reduced the natural supply and movement of sand, while seawalls and rock revetments have increasingly fixed the shoreline in place. At the same time, sea level is rising at an accelerating rate, and extreme events involving large waves, high tides, and El Niño conditions can produce decades of average erosion in a single season. This paper examines California’s coastline and beaches from their geologic origins through their present condition and considers how sea-level rise, erosion, extreme events, and human intervention will shape their future. There are no simple solutions, and sustaining beaches, public access, coastal ecosystems, and developed communities will require science-based planning, regional sediment management, and allowing the shoreline to move inland where possible.

HALF-MOON-BAY-JMSE-Griggs.pdf

The Impacts of the Construction of the Pillar Point Harbor Breakwaters on the Half Moon Bay Shoreline, San Mateo County, California

This paper describes how the construction of breakwaters at Half Moon Bay dramatically altered natural wave patterns. Bluff erosion that had been only about 8 cm per year accelerated to as much as 2 meters per year, destroying infrastructure and threatening homes and a highway. Attempts to fix the resulting problems required additional breakwaters and extensive rock armoring, illustrating how coastal engineering can create cascading, long-term consequences.

Griggs-Davenport-Davar.pdf

What is a resilient coastal community in a changing climate?

“Resilience” is widely used in coastal hazard planning but lacks a clear, shared definition. To examine how it is understood in practice, we surveyed 52 coastal professionals, including engineers, geologists, attorneys, property owners, and policy-makers. Participants were asked to define a resilient coastal community, identify an appropriate planning horizon, and provide examples. Ten distinct definitions emerged, ranging from disaster recovery to resistance to long-term adaptation. We group these into three broad categories: recovery, absorption, and adaptation. The results highlight the need for clearer definitions and more flexible approaches as coastal communities confront accelerating hazards.

Challenge at the Edge.pdf

Challenge at the Edge: Long-Term Sea Level Rise vs. Short-Term Extreme Events

California and most other coastlines around the nation and the world are being impacted by both long-term sea-level rise (SLR) and short-term extreme events. Global sea level over the last 10 years of satellite altimetry has averaged approximately 4.1 mm/yr. (~16 in./100 yrs.), although this rate is accelerating at about 1.2 mm/yr. per decade. Projections of future sea levels have now been developed by many different agencies, organizations, and committees, and cluster around 12 inches by 2050. Over the near term, however, until mid-century, and likely beyond, it will be the short-term extreme events such as hurricanes along the U.S. Atlantic and Gulf coasts, and the coincidence of very large waves and high astronomic tides along the U.S. Pacific coasts that will pose the major threat to both public infrastructure and private development.

A Tale of Three Winters.pdf

A Tale of Three Winters: Repeated Extreme Event Damage Along the Central California Coast

California’s coastal counties, which account for about 70% of the state’s population and its marine economy contributes $51.3 billion annually to California’s gross domestic product, have experienced multiple destructive extreme events over the past three winters. Repeated coastal storms significantly damaged public infrastructure, homes, businesses, and resources on which coastal communities depend. It is estimated that the California coastal storms between December 2022 and March 2023 alone caused $4.7 billion in economic losses. The frequency and severity of recent coastal flooding and associated impacts emphasize that projected future extreme events are already happening and adversely affecting coastal cities and counties. This study explores the phenomena and consequences of the extreme storms that hit the Central California Coast in the 2022–23, 2023–24, and 2024–25 winters. The intensification and the frequency of recent coastal storms and the magnitude of social and economic impacts highlight that it is time to rethink the typical historic responses of repairing, rebuilding, and reopening. Time is running out and action is needed to develop new or reassess the existing adaptive management strategies and accelerate their implementation to prevent or at least reduce the potential damage from future natural disasters to coastal assets, coastal infrastructure, and the well-being and livelihood of coastal communities.

Griggs & Battalio JCR.pdf

Short- and Long-Term Risks of Back Beach Development along the California Coast

California’s beaches naturally narrowed in winter and widened in summer. From the mid-1940s to 1978, a cooler Pacific Decadal Oscillation and milder El Niño events resulted in little coastal storm damage. During this period, California’s population grew rapidly, and once-wide beaches were developed with homes, businesses, and infrastructure. In recent decades, however, extreme events—large waves coinciding with high tides, often during major El Niños—have repeatedly damaged shoreline development. Sand loss and shifting wave patterns have worsened the impacts, and rising sea levels will only add to future challenges. Solutions like coastal armor and beach nourishment are costly and temporary. Climate change is real, happening now, and unavoidable. While homeowners resist managed retreat, failing to plan means retreat will happen unmanaged. Each vulnerable coastal community must assess risks and plan for a future where maintaining these areas is no longer feasible.

Beach_Nourishment.pdf

Beach Nourishment: A Critical Look

Beach nourishment has been the primary response to shoreline recession along the U.S. Atlantic and Gulf coasts for a century, with $15.7 billion spent on 1.2 billion m³ of sand for 475 communities, mostly in New Jersey, New York, North Carolina, and Florida. Costs, sand volumes, and replenishment frequency have risen, with some North Carolina beaches nourished over 20 times. While beneficial for recreation and property protection, the short lifespan of nourished beaches, ongoing costs, environmental impacts, land subsidence, extreme events, and rising sea levels suggest federal funding should end, shifting focus to long-term retreat from the shoreline.

SEACLIFF ARTICLE with Cover.pdf

The past, present, and future of Seacliff State Beach: Adapting to long-term sea level rise on California’s Central Coast

In a display of the increasingly destructive impact of climate change and sea level rise, in January 2023 unusually severe storms hit California’s west coast and devastated the infrastructure at Monterey Bay’s Seacliff State Beach. Additional severe storms in December 2023 compounded the damage. This article frames the potential application of a new approach for recovery planning along the California coast by examining historical failures, accelerating threats, and the economic and societal factors that create obstacles to long-term success at places such as Seacliff. While each situation differs, the Seacliff State Beach challenge is representative of an ever-widening dilemma faced by many seaside communities. The possibilities for coastal adaptation at Seacliff, based in part on California’s innovative state policies, provide an opportunity to consider sustainable and equitable planning approaches for local communities, government, business, and ultimately future generations.

GRIGGS LIVING SHORELINES-1.pdf

The California Coast and Living Shorelines—A Critical Look

California and most other coastlines around the world are being impacted by both long- term sea-level rise and short-term extreme events. Due to California’s long and intensively developed coastline, it is an important area for evaluating responses to these challenges. The predominant historic approach to coastal erosion in California and globally has been the construction of hard coastal armoring such as seawalls and rock revetments. The concept of living shorelines—defined as using natural elements like plants, sand, or rocks to stabilize the coastline—has been widely proposed as a soft or green response to coastal erosion and flooding. However, these approaches have very limited application in high-energy environments such as California’s 1100-mile-long outer coast and are not realistic solutions for protection from wave attack at high tides or long-term sea-level rise. Each of the state’s coastal communities need to identify their most vulnerable areas, develop adaptation plans, and plan eventual relocation strategies in response to an accelerating sea-level rise.

RESILIENT COASTAL COMMUNITIES JCR.FINALpdf-2.pdf

Can We Make Coastal Communities Resilient to Sea-Level Rise?

“Resilient” is a term that has gotten increasingly widespread usage in recent years as a solution or response for coastal communities to the well-documented global rise in sea level. The message that is usually conveyed seems to be that if we can make coastal communities resilient, everything will be fine and we will have solved the challenge of how to adapt to a rising sea. The federal government and some coastal state government agencies are providing grant money to encourage coastal communities to develop plans to become more resilient. This is an appropriate time to ask what would a resilient coastal community look like and can we actually make a community resilient to future sea-level rise, and if so, for how long?

Documenting a Century of Coastline Change along Central California and Associated Challenges From the Qualitative to the Quantitative.pdf

Documenting a Century of Coastline Change along Central California and Associated Challenges: From the Qualitative to the Quantitative

Wave erosion has been steadily moving coastal cliffs and bluffs landward for centuries. However, climate change and rising sea levels are now accelerating this process worldwide. Studying and projecting cliff erosion is more complex than analyzing changes along sandy beaches due to the unique challenges posed by rocky coastlines. This research focused on coastal erosion along West Cliff Drive in Santa Cruz, California. It examined geological history, cliff shapes, and past retreat rates to better understand coastline changes. Challenges in analyzing cliff retreat include complex cliff shapes, undercutting, and cave formation, which add uncertainty to measurements. Addressing these uncertainties is crucial for accurately predicting future erosion rates and creating effective plans to manage the impacts of a changing coastline in this densely populated area.

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