LIDAR DERIVED SALT MARSH TOPOGRAPHY AND BIOMASS: DEFINING ACCURACY AND SPATIAL PATTERNS OF UNCERTAINTY

Seagrass meadows are an emblematic coastal habitat. Their sensitivity to environmental change means that it is essential to monitor their evolution closely. However, high costs make this endeavor a technical challenge. Here, we used machine learning to map seagrass meadows in 148 satellite images in the Venice Lagoon, Italy. We found that adding information such as depth of the seabed and known seagrass location improved our capacity to map temporal change in seagrass habitat.

Convection-permitting climate models could represent future changes in extreme short-duration precipitation, which is critical for risk management. We use a non-asymptotic statistical method to estimate extremes from 10 years of simulations in an orographically complex area. Despite overall good agreement with rain gauges, the observed decrease of hourly extremes with elevation is not fully represented by the model. Climate model adjustment methods should consider the role of orography.

We comparatively evaluate the predictive performance of traditional and new approaches to estimate the probability distributions of extreme coastal water levels. The metastatistical approach maximizes the use of observational information and provides reliable estimates of high quantiles with respect to traditional methods. Leveraging the increased estimation accuracy afforded by this approach, we investigate future changes in the frequency of extreme total water levels.

Coastal marshes are valuable natural habitats with normally dense vegetation. The presence of bare patches is a symptom of habitat degradation. We found that the occurrence of bare patches and regrowth of vegetation is related to spatial variations in soil surface elevation and to the distance and connectivity to tidal creeks. These relations are similar in three marshes at very different geographical locations. Our results may help nature managers to conserve and restore coastal marshes.

An in-situ loading test was carried out in the Lazzaretto Nuovo salt-marsh in the Venice Lagoon, Italy. The test was aimed at characterizing the geotechnical properties of soils forming the marsh sedimentary body deposits. In fact porosity and compressibility are of paramount importance to quantify consolidation versus accretion and relative sea level rise. The fate of coastal marshlands in the next future will strongly depend of these processes.