Sea Level at the Coast from Video-Sensed Waves: Comparison to Tidal Gauges and Satellite Altimetry

Abstract

Nearshore complex and energetic hydrodynamic conditions make observing evolving processes during extreme and short-term events difficult. In particular, total sea levels at the coast are hard to measure with current techniques. Sea level is commonly measured with tidal gauges and spaceborne altimetry, which lack essential details of spatial and wave-related sea level variability along the coast. Hence, novel techniques, adapted to nearshore areas, are required. This paper presents the first-time use of video cameras to derive the total sea level at the coast. This novel approach consists of estimating time-varying total water levels by applying a celerity-based depth inversion method, which is conventionally used to estimate bathymetry from video. The video-derived total sea levels are compared to sea levels derived from an in situ acoustic Doppler current profiler (ADCP), the nearest tide gauge, and altimetry. A tidal harmonic analysis is performed on the video-derived water levels, yielding an accurate determination of the dominant tidal harmonics. However, it remains difficult to separate bathymetric changes due to the waves on beaches when rapid morphological changes occur under energetic conditions. Nonetheless, video-derived water-level anomalies are in good agreement with state-of-the-art altimetry products. Although there is still work to be done, the results show the potential to measure total sea level at the coast using video camera systems.

Shoreline Response to a Sandy Nourishment in a Wave-Dominated Coast Using Video Monitoring

“…The preliminary test for video-derived breaking wave height is intended to be combined with the automated shoreline detection to build a video-based integrated system that will fully describe the nearshore hydrodynamics and morphology. Besides the breaking wave height and shoreline, the system is expected to provide nearshore bathymetry and hydrodynamics [27,33,[59][60][61][62], wave runup [63][64][65] and intertidal topography [33,57]. [58].…”

Sea level anomalies using altimetry, model and tide gauges along the African coasts in the Eastern Tropical Atlantic Ocean: Inter-comparison and temporal variability

“…In the Senegal region, our study is the first to compare and validate different SLA products including altimetry data near the coast. Studies on the sea level trend have been conducted in this region (e.g., Thoreux et al, 2018;Le Cozannet et al, 2015) but due to the limited number of TG available along the ETAO coast, more studies validate altimetry using video camera data installed near coastal cities in the region (e.g., Angnuureng et al, 2018;Abessolo-Ondoa et al, 2019). However, their time series remain short and present significant missing data due to maintenance problems of these facilities in these countries (Abessolo- Ondoa et al, 2016).…”

Assessment of a Smartphone-Based Camera System for Coastal Image Segmentation and Sargassum monitoring

“…Among the coastal video monitoring techniques, ground-sensing approaches by means of camera systems are widely used, allowing the investigation of coastal processes with high temporal and spatial resolution, with optimal accuracy. Numerous alternative or complementary uses are also pursued, with applications related to coastal hydrodynamics [1][2][3][4], morphodynamics [5][6][7], or quality monitoring (e.g., seagrass) [8,9]. Moreover, the use of low-cost devices and public resources has recently become a focus of attention and is being further explored [10][11][12].…”