Conference Agenda

Coastal zones are essential for the socio-economic well-being of many nations [1] Coastal regions have multiple uses, needs and opportunities, and are particularly exposed to extreme events and climate change. Many key sectors are affected by long-term effects in these zones, such as the monitoring of public/private infrastructures, cultural/natural heritage preservation, risk management, and agriculture. The combined effects of sea level rise (SLR), tidal evolution, modulated ocean currents and extreme events can have numerous impacts on coastal, river delta, and inland water zones, including water management, which in turn lead to cascading and unpredictable impacts on other sectors. The ESA-DRAGON V GREENISH project [2] aims to provide extensive research and development analyses of areas in Europe and China subject to climate change induced (e.g., Sea Level Rise, flooding, and urban climate threats) and anthropogenic disasters (e.g., ground subsidence over reclaimed-land platforms), with the goal to improve the knowledge and develop new remote-sensing methods. Global sea-level is rising, and tides are also changing worldwide, and these risks are accompanied by increasing concerns about the growing urbanization of the world’s low-lying coastal regions and related coastal hazards (e.g., flooding). On the other hand, Inland water bodies such as lake and river system also experience substantial degradation with rapid economic development.

The main project goals are: i) To study the ground deformation in coastal/deltaic regions with conventional and novel interferometric SAR approaches; ii) To monitor changes in urbanized areas via coherent and incoherent change detection analyses; iii) To study interactions between ocean currents and coasts, such as coastal erosion, using high resolution optical and SAR satellite images; iv) To properly assess SLR, tidal evolution, and hydrogeological risks in urban coastal areas; v) To study the interactions between Poyang Lake and its connecting rivers. vi) To develop atmospheric phase screen correction methods in multi-temporal SAR images. vi) To develop interactive maps of coastal, urban, and inland zones susceptible to primary and secondary risks via GIS, and finally vii) To train Young Scientists.

A number of planned activities have already started and some results have already been achieved, which will be presented at the on-line event scheduled for October 2022. Specifically, we processed a sequence of SAR data related to the area of Venice Lagoon and the Po ‘river system to create a base for further analyses devoted to analyzing the effect of extreme weather conditions and sea level rise in the lagoon [3]. To this aim, we investigated the impact of a recent flood event that occurred in the area in 2019. In this context, we applied/tested methods of incoherent change detection [4]-[5]. Some experiments have also been carried out in the city of Shanghai to apply artificial intelligence methods with TerraSAR-X image time-series in urban context to reveal changes triggered by human activities. Assessment and analysis of capability of disaster reduction and crucial index at district Level in Shanghai have also been made. We also investigated the recent decade deformation time-series in Chongming Island of Shanghai by using four space-borne Synthetic Aperture Radar (SAR) satellite datasets.

The risk of flooding in the coastal area of the Shanghai megacity was further characterized. To this aim, two independent sets of synthetic aperture radar (SAR) data collected at the X- and C-band through the COSMO-SkyMed (CSK) and the European Copernicus Sentinel-1 (S-1) sensors have been exploited. By assuming that the still extreme seawater depth is chi-square distributed, the probability of waves overtopping the coast was estimated. We also evaluated the impact on the territory of potential extreme flood events by counting the number of very-coherent objects (at most anthropic, such as buildings and public infrastructures) that could be seriously affected by a flood. To forecast possible inundation patterns, we used the LISFLOOD-FP hydrodynamic model [6]. Experimental results, which are detailed in [7], showed that two coastline segments located in the southern districts of Shanghai, where the height of the seawall is lower, had the highest probability of wave overtopping and the most significant density of coherent objects potentially subjected to severe flood impacts. The slowly developing landslides in the districts of Istanbul have also been investigated using S-1 sensors [8].

Other planned activities are in course for: i) the analysis of the Istanbul/Marmara-Sea coastal environment, ii) the investigation of large-scale coverage of Bohai Rim Region ground subsidence caused by underground resources extraction such as underground water, oil, gas and brine over Bohai rim region, iii) the analysis of ocean currents and the SLR impact.

References

1. Sengupta, D.; Chen, R.; Meadows, M.E. Building beyond land: An overview of coastal land reclamation in 16 global megacities. Appl. Geogr. 2018, 90, 229-238.
2. https://dragon5.esa.int/projects/
3. Mastro P, Calò F., Giordan D., Notti D., Pepe A., “On Monitoring the Impact of Floods and Extreme Weather Events in Protected Cultural Heritage Areas: The Venice Lagoon Case Study”, proceedings of Living Planet Symposium, 23 – 27 May, 2022, Bonn, Germany.
4. Lu, D.; Mausel, P.; Brondizio, E.; Moran, E. Change Detection Techniques. Int. J. Remote Sens. 2004, 25, 2365–2407
5. Mastro, P.; Masiello, G.; Serio, C.; Pepe, A. Change Detection Techniques with Synthetic Aperture Radar Images: Experiments with Random Forests and Sentinel-1 Observations. Remote Sens. 2022, 14, 3323. https://doi.org/10.3390/rs1414332.
6. Bates, P.D.; De Roo, A.P.J. A simple raster-based model for flood inundation simulation. J. Hydrol. 2000, 236, 54–77
7. Tang, M.; Zhao, Q.; Pepe, A.; Devlin, A.T.; Falabella, F.; Yao, C.; Li, Z. Changes of Chinese Coastal Regions Induced by Land Reclamation as Revealed through TanDEM-X DEM and InSAR Analyses. Remote Sens. 2022, 14, 637. https://doi.org/10.3390/rs14030637.
8. Bayik, C.; Abdikan, S.; Ozdemir, A.; Arikan M.; Balik Sanli F.; Dogan U. Investigation of the landslides in Beylikdüzü-Esenyurt Districts of Istanbul from InSAR and GNSS observations. Nat Hazards 109, 1201–1220 (2021).

It is presented in this paper some recent progresses of ESA-MOST China Dragon Cooperation Program “Synergistic Monitoring of Ocean Dynamic Environment from Multi-Sensors (ID. 58009)” including: (1) Assessment of ocean swell height observations from Sentinel-1A/B Wave Mode against buoy in situ and modeling hindcasts; (2) Quantifying uncertainties in the partitioned swell heights observed from CFOSAT SWIM and Sentinel-1 SAR via triple collocation; (3) Up-to-Downwave asymmetry of the CFOSAT SWIM fluctuation spectrum for wave direction ambiguity removal; and (4) Validation of wave spectral partitions from SWIM instrument on-board CFOSAT against in situ data.

This is the first presentation of quasi-synchronous spaceborne synthetic aperture radar (SAR) high-resolution images acquired from C-band Radar Constellation Mission (RCM) and RADARSAT-2 consisting of quad-polarization (HH+HV+VH+VV) wide swath observations of Hurricane Epsilon. These measurements clearly show that the denoised HV- and VH-polarized normalized radar cross sections (NRCSs) have great consistency. NRCS values at HV- and VH-polarizations are more sensitive to wind speeds and less sensitive to incidence angles or wind directions than those at HH and VV for hurricane-force winds. For large incidence angles and high wind speeds, the sensitivity of HH-polarized NRCS to wind speed is higher than that of VV. HH- and VV-polarized NRCS gradually lose wind direction dependency at high winds. It is notable that the time interval between the two SAR acquisitions is only 3 minutes. This allows for a direct comparison of HV- and VH-polarized images to investigate the variations of high-resolution backscattering within the hurricane vortex, thereby revealing the most dynamical areas. An asymmetric dynamic is observed around the eye of Hurricane Epsilon, based on positive and negative differences (VH–HV) in the western and eastern parts of the eye. The impacts of rain on quad-polarized NRCS are also examined using collocated rain rates from the Global Precipitation Mission (GPM) and wind speeds from the Soil Moisture Active Passive (SMAP). Significant rain-induced NRCS attenuations are about 1.7 dB for HH and VV, and 2.2 dB for HV and VH, when the rain rate is 20 mm/hr. These attenuations are associated with rain-induced turbulence and atmospheric absorption. This work shows that the collocated RCM and RADARSAT-2 hurricane observations provide a unique analysis of synoptic and joint C-band measurements of the ocean surface in quad-polarization; this is noteworthy in view of preparations for the next generation of dual-polarization scatterometer (SCA) onboard MetOp-SG.