Over the last several decades, the study of Earth surface processes has progressed from a descriptive science to an increasingly quantitative one due to advances in theoretical, experimental, and computational geosciences. The importance of geomorphic forecasts has never been greater, as technological development and global climate change threaten to reshape the landscapes that support human societies and natural ecosystems. Here we explore best practices for developing socially-relevant forecasts of Earth surface change, a goal we are calling “earthcasting”. We suggest that earthcasts have the following features: they focus on temporal (~1 to ~100 years) and spatial (~1 m to ~10 km) scales relevant to planning; they are designed with direct involvement of stakeholders and public beneficiaries through the evaluation of the socioeconomic impacts of geomorphic processes; and they generate forecasts that are clearly stated, testable, and include quantitative uncertainties. Earthcasts bridge the gap between Earth surface researchers and decision-makers, stakeholders, researchers from other disciplines, and the general public. We investigate the defining features of earthcasts and evaluate some specific examples. This paper builds on previous studies of prediction in geomorphology by recommending a roadmap for (i) generating earthcasts, especially those based on modeling; (ii) transforming a subset of geomorphic research into earthcasts; and (iii) communicating earthcasts beyond the geomorphology research community. Earthcasting exemplifies the social benefit of geomorphology research, and it calls for renewed research efforts toward further understanding the limits of predictability of Earth surface systems and processes, and the uncertainties associated with modeling geomorphic processes and their impacts.

Human pressures on the coastal zones and oceans have increased considerably in the last decades. Human activities constitute the greatest threat to the coastal and marine environment, generating considerable quantities of plastic waste. Currently, it is widely recognized that the increase of marine-related activities has adversely affected the coastal environment as well as the associated ecosystems. Our study focuses on marine litter and specifically on the floating part of it which is frequently composed of plastic materials. Floating litter tends to accumulate on beach-dune ecosystems, already characterized by multiple anthropogenic pressures and environmental factors. In addition, litter items may be trapped by coastal dune vegetation or saltmarsh. Successively, the degradation of marine litter will cause the entering of secondary microplastics. Most of the previous studies are based on monitoring activities and aim to identify the origin and destination of litter in order to manage the fate and transport issues. Therefore, it is important to develop modeling and monitoring tools to detect and prevent marine debris dispersal in coastal environments. We applied field sampling and UAVs (Unmanned Aerial Vehicles) survey over a complex geomorphic set up in the Po River Delta (Italy). Our field data are implemented into a high-resolution hydro-morphodynamic numerical model for validation. Then, we are able to project into different scenarios of plastic debris accumulation in the coastal zone. Our preliminary results show an accumulation of floating debris in coastal dunes vegetation mainly driven by alongshore currents and wave set up in the nearshore area. Then, wind-dominated directions and magnitude disperse plastic debris in embryo dunes and back-barrier marshes. Specific cleaning operations are therefore needed. Considering that coastal management scenarios and decisions rely on numerical models that can predict best practices for coastal sustainability, our results might help local agencies and stakeholders to manage coastal environments.

River deltas are a compelling target for numerical simulation because they contain seemingly organized patterns and shapes at a variety of scales. For instance, most river-dominated deltas, regardless of size, have triangular to semi-circular planform shapes, channel networks, and channel bifurcations. The common presence of these features among most deltas in the world (Caldwell et al., 2019; Nienhuis et al., 2020) suggests there are consistent underlying physical processes controlling delta form and behavior. In this review, we discuss how numerical modeling, and more specifically a type of modeling focused on the morphodynamic feedback, has helped explore some of these key physical processes over the last 15 years.

Living shorelines are native marsh plantings that control coastal erosion and provide coastal resilience to sea level rise (SLR) by migrating upland during SLR. Living shorelines require ripraps to dissipate wave energy which prevent marsh boundary erosion and facilitate sedimentation. Currently, ripraps are built with rocks which cannot adapt to SLR to continue attenuating wave energy. Alternatively, oyster castles are modular cinder blocks for building breakwaters and coastal structures that initiate the development of oyster reefs which can grow equivalently with SLR. Thus, oyster castle breakwaters can adapt to SLR while retaining their breakwater function. This research used Delft3D and SWAN to model the effects of climate changes, especially SLR, on coastal morphology with 3 domain configurations: 1) only marsh, 2) traditional living shoreline with riprap and 3) living shoreline with oyster castle. We built a model comparing marsh deposition between these coastal structures over time, and determined the most important parameters affecting living shoreline evolution. All domains were 2 km wide by 1 km in length to mimic coastal bay conditions. Model runs were set up for a temporal scale of 150 days. This duration was increased by a morphological factor of 150 to project our results to 30 and 60 years. The parameters tested included vegetation density, nearshore slope, SLR, and suspended sediment concentration (SSC). Oyster castles facilitated greater marsh deposition than riprap at +8.9 mm under current sea level, +3.5 mm with SLR of 0.4 m, and +3.3 mm with SLR of 0.8 m. Increased nearshore slope and higher SSC both increased sediment deposition in the marsh. Increased sea level and higher marsh density decreased maximum bed shear stress. Therefore, coastal restoration efforts should strive to integrate oyster castle into living shorelines, and increase marsh density to enhance sediment deposition and coastal resilience. Our modelling efforts focus on quantifying the impacts of coastal processes on created marsh dynamics.

River deltas and enclosed lagoons represent a zone where fluvial and littoral processes interacts through a redistribution, erosion, and deposition of sediment, with a huge impact on coastal management and engineering. The focus of the study is to understand the correct balance between strategies to maintain the navigational efficiency of tidal inlets and the respect of the ecological and economical function in coastal lagoons. We applied an integrated modeling system which will link multiple hydrodynamic and morphodynamic models to understand how coastal processes and the associated sediment transport can influence the functioning of the southern inlet of the Barbamarco lagoon in the Po River Delta, Italy. Furthermore, our study provides engineering solutions aimed at the inlet functioning efficiency with a proposal for the monitoring plan. Our results highlight the importance of the seasonal effects of wave climate on the littoral sediment transport. Model outcomes show that the dredging volume is approximately 15,000 cubic meter/year for the southern inlet that might vary with wave climate. However, shaping a wider tidal channel seaward will reduce the dredging activities with a longer interval than the actual sediment removal. A design of a deeper and wider channel will deflect the along shore current seaward with a sediment bypass of the inlet. Therefore, the sediment will reach the erosional side of the inlet enhancing the redistribution of the sediment which might reduce the over-wash during storms and high-water levels. Our results display the ephemeral equilibrium of tidal inlets and coastal lagoons in deltaic systems impacted by large riverine sediment delivery. Shore management scenario and decision relies on hydro-morphodyanmic numerical model to predict the best practice for coastal sustainability.