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

Abstract

Wave erosion has moved coastal cliffs and bluffs landward over the centuries. Now climate change-induced sea-level rise (SLR) and the changes in wave action are accelerating coastline retreat around the world. Documenting the erosion of cliffed coasts and projecting the rate of coastline retreat under future SLR scenarios are more challenging than historical and future shoreline change studies along low-lying sandy beaches. The objective of this research was to study coastal erosion of the West Cliff Drive area in Santa Cruz along the Central California Coast and identify the challenges in coastline change analysis. We investigated the geological history, geomorphic differences, and documented cliff retreat to assess coastal erosion qualitatively. We also conducted a quantitative assessment of cliff retreat through extracting and analyzing the coastline position at three different times (1953, 1975, and 2018). The results showed that the total retreat of the West Cliff Drive coastline over 65 years ranges from 0.3 to 32 m, and the maximum cliff retreat rate was 0.5 m/year. Geometric errors, the complex profiles of coastal cliffs, and irregularities in the processes of coastal erosion, including the undercutting of the base of the cliff and formation of caves, were some of the identified challenges in documenting historical coastline retreat. These can each increase the uncertainty of calculated retreat rates. Reducing the uncertainties in retreat rates is an essential initial step in projecting cliff and bluff retreat under future SLR more accurately and in developing a practical adaptive management plan to cope with the impacts of coastline change along this highly populated edge.

Coastal Erosion Vulnerability in Mainland China Based on Fuzzy Evaluation of Cloud Models

“…The results show that both internal and external factors of coastal erosion can be derived from the influence of natural change processes and human activities; moreover, the human activities that cause coastal erosion often have many effects, some of which are positive, and some of which are negative (while others are caused by unwise or incorrect human decision-making, etc.) (Mujabar and Chandrasekar, 2013;Griggs et al, 2019). Furthermore, coastal erosion in China is facing increasing challenges.…”

Coastal Adaptation to Climate Change and Sea-Level Rise

“…Communities can start by looking at current management practices, the history of storm damage and erosion, the exposure or vulnerability of both public infrastructure and private development. and both present and future hazards and challenges [111]. Where structures are located in vulnerable coastal locations and have experienced or are threatened by frequent flooding or cliff retreat, relocating or removing the structure is going to become a more realistic and important consideration or response.…”

Multi-scale approach to analyse the evolution of soft rock coastal cliffs and role of controlling factors: a case study in South-Eastern Italy

“…Brooks and Spencer (2010) presented a geomorphological study on cliff recession rates and corresponding sediment losses for the soft rock cliffs forming the Suffolk coast (UK), where shoreline retreat, reaching up to 3-4 m per year, have been inferred in the last century. Griggs et al (2019), instead, propose a quantitative assessment of cliff retreat in the Central California Coast area, based on geological history, geomorphological analysis and aerial photo analysis, which indicates a maximum cliff retreat rate of about 0.5 m/year. The meteo-marine conditions, as rainfalls, sea and wind erosion, including abrasion, corrosion, marine spray and thermal stresses, as well as wave impact stress during energetic sea storms, can represent the triggering factors of the instability processes, giving rise to the development of rock mass failures and consequent coastal retreat.…”