Requirements for a Coastal Hazards Observing System

Abstract

Coastal zones are highly dynamical systems affected by a variety of natural and anthropogenic forcing factors that include sea level rise, extreme events, local oceanic and atmospheric processes, ground subsidence, etc. However, so far, they remain poorly monitored on a global scale. To better understand changes affecting world coastal zones and to provide crucial information to decision-makers involved in adaptation to and mitigation of environmental risks, coastal observations of various types need to be collected and analyzed. In this white paper, we first discuss the main forcing agents acting on coastal regions (e.g., sea level, winds, waves and currents, river runoff, sediment supply and transport, vertical land motions, land use) and the induced coastal response (e.g., shoreline position, estuaries morphology, land topography at Frontiers in Marine Science | www.frontiersin.org 1 July 2019 | Volume 6 | Article 348Benveniste et al.Requirements for a Coastal Zone Observing System the land-sea interface and coastal bathymetry). We identify a number of space-based observational needs that have to be addressed in the near future to understand coastal zone evolution. Among these, improved monitoring of coastal sea level by satellite altimetry techniques is recognized as high priority. Classical altimeter data in the coastal zone are adversely affected by land contamination with degraded range and geophysical corrections. However, recent progress in coastal altimetry data processing and multisensor data synergy, offers new perspective to measure sea level change very close to the coast. This issue is discussed in much detail in this paper, including the development of a global coastal sea-level and sea state climate record with mission consistent coastal processing and products dedicated to coastal regimes. Finally, we present a new promising technology based on the use of Signals of Opportunity (SoOp), i.e., communication satellite transmissions that are reutilized as illumination sources in a bistatic radar configuration, for measuring coastal sea level. Since SoOp technology requires only receiver technology to be placed in orbit, small satellite platforms could be used, enabling a constellation to achieve high spatio-temporal resolutions of sea level in coastal zones.

Monitoring Beach Topography and Nearshore Bathymetry Using Spaceborne Remote Sensing: A Review

“…Coastal topography and bathymetry information are key parameters for several applications. Mapping the nearshore bathymetry and the foreshore topography is considered as an "observational priority" [7]. Their highly dynamic behavior requires frequent monitoring.…”

“…Due to sea level rise and its related effects, coastal systems are considered amongst the most threatened environments [5]. A continuous monitoring of these systems is thus of great importance in order to plan sustainable coastal development and to implement ecosystem protection strategies [6,7]. A great demand exists nowadays for up-to-date bathymetric and topographic maps of shallow water areas and adjacent beaches.…”

“…A great demand exists nowadays for up-to-date bathymetric and topographic maps of shallow water areas and adjacent beaches. Marine-land topography and bathymetry with high spatiotemporal resolution and a reasonable vertical accuracy are essential for a better understanding of the evolution of coastal systems [7]. They are, as well, essential for various types of applications and studies, including: Coastal flood forecasting, erosion forecasting, coastal defense, the monitoring of morphological changes, the identification of shoreline erosion or accretion, navigation, and fishing [8].…”

Space-Based Earth Observations for Disaster Risk Management

“…The challenge of better anticipating more frequent and intense heatwaves and droughts, or generally extreme natural phenomena, comes along with Earth Observation needs, which have not been systematically assessed yet. For example, adaptation to sea-level rise requires improved monitoring of shoreline changes and sediment transport (Benveniste et al 2019), but the most urgent needs for such information comes from current risk management whereas adaptation at timescales relevant to sea-level rise (i.e., decades and centuries) is usually considered less urgent. For these sectors where no specific requirements have been formalized yet, we argue that a systematic review of user workflows and decisions is required to maximize the societal benefits of space-based Earth observations.…”

Video Sensing of Nearshore Bathymetry Evolution with Error Estimate

“…Conventional measurement techniques have obvious limitations because they are time consuming, costly and hazardous. These disadvantages do not apply to remote techniques such as shore-based video systems and LiDAR or satellite imagery [20,21]. Continuous video monitoring now reveals the beach response to wave forcing at different timescales [16,22].…”