ALBERT

Description: Minor coastal flooding, also known as high tide flooding, is quickly becoming a major challenge for coastal communities across the United States. Many coastal locations throughout the U.S. already experience 10 days or more of flooding per year, a number that is likely to increase dramatically over the next several decades with continued relative sea level rise. Communities require tools to enable them to better prepare for coastal flooding impacts in the months to years ahead. Here we present a novel statistical model to predict daily high tide flooding likelihood with lead-times of months to years. The model relies on astronomical tide predictions, sea level trends, monthly sea level anomaly persistence and climatological non-tidal residuals to predict daily flooding likelihood at U.S. tide gauge locations. Published results show the method to be skillful at predicting flooding a year or more in advance at most tested U.S. National Oceanic and Atmospheric Administration (NOAA) tide gauges. At 18 gauges the model accurately predicted more than half of all floods occurring from 1997-2019 with less than a 10% False-Alarm-Rate. In this presentation we also demonstrate NOAA visualization products developed to deliver model predictions for end-user decision-support. Lastly, we show initial results of the application of the model to a forty-year, 500m resolution hydrodynamic model reanalysis of coastal water levels to enable predictions away from tide gauge locations.

Description: Tsunamis are the worst unpredictable marine threat to ocean coasts. For detecting and confirming their generation and to predict the propagation characteristics real-time sea-level data are essential to formulate authoritative warnings. Coastal communities are also provided with specific scenarios of the threat using inundation maps and models to prepare responses, both in the actual situation and for long-term land use planning and marine spatial management, building up awareness and resilience for regional hazards. Assembling this detailed information in data bases ensures future development of industry and tourism. The present network (http://www.ioc-sealevelmonitoring.org/map.php) shows many gaps, broken stations or lack of rapidly available data. To extend, improve and accelerate the fast-delivery mode of sea level data a sustained long-term commitment by governments is essential. In parallel the science community requires immediate and sustained access for local case studies and the development of regionalized and detailed new products. Technological developments in sensors, site management, data transmission and QC procedures are ongoing and will improve the quality of the sea level measurements. This data is also important to quantify the impact of climate change on the coasts. Its availability though is less dependent on the speed of delivery and is well addressed by the GLOSS system (Global Sea Level Observing System) of UNESCO/IOC. Adhering to the IOC Data Sharing Policy ensures better and enduring ocean-wide tsunami warning systems, and will constitute a strong action within the UN Decade of Ocean Science for Sustainable Development on local, regional and global scales.

Description: Puʻuhonua O Hōnaunau National Historical Park, located south of Kona on the western shore of Hawaiʻi Island, is a significant site in Hawaiian culture and history. Park stewards have documented increasingly frequent impacts to park assets in recent years due to the compounding effects of sea-level rise, sea-level anomalies, astronomical tides, and surface gravity waves. Here we present a co-developed study of compound shoreline impacts affecting Puʻuhonua O Hōnaunau that addresses the needs and questions of park stewards. We utilize in situ observations of water level from an array of nearshore pressure sensors to validate a high-resolution 2D wave-transformation model (SWASH) that captures wave-driven contributions to total water level at the park shore. We find that the magnitude of wave-driven impacts is highly sensitive to small changes in swell angle, and that the nature of wave-driven impacts varies substantially within the park bounds due to the complex bathymetry and coastline of the region. We combine the model results with regional wave hindcasts, sea-level data, and projections of sea-level rise to quantify the frequency and extent of future tidal- and wave-driven flooding events in Puʻuhonua O Hōnaunau. Finally, we demonstrate distillation of our results for use by park stewards in the form of co-developed materials and products, including a novel augmented reality (AR) smartphone app currently available from the iOS and Google Play app stores.

Description: To enhance monitoring and understanding of coastal sea levels, as well as provide information for adapting to sea level rise, the University of Hawaii Sea Level Center is installing new tide gauges throughout the Hawaiian Islands. All of the tide gauge stations are designed according to quality-control standards developed by the UNESCO-IOC Global Sea Level Observing System (GLOSS), along with two additional geodetic leveling steps. Firstly, to facilitate long-term monitoring of sea levels relative to the coastline, the vertical datum of each station is held constant with respect to the regional land elevation. New for this Hawaii tide gauge network, all of the water level measurements are referenced to an island-specific vertical datum, which is based on each station elevation with respect to a constant tidal datum. On the island of Oahu, for example, elevations of five new tide gauges are referenced to the tide gauge in Honolulu Harbor. We determined station elevations by surveying with respect to an existing benchmark network in Hawaii that is on a common datum (NAD PA11 ellipsoidal height). Measuring water levels with respect to island-specific datums will support adaptation planning to address sea level rise by determining how sea levels vary by location. We also recorded ellipsoidal height differences from the gravitational model for Hawaii (GEOID12B) to transfer sea levels into a physically consistent framework. Here, the methodology for implementing the Hawaii tide gauge network will be presented, along with discussion about applicability to other regions where long-term monitoring of sea levels is important.