Land reclamations influence the morphodynamic evolution of estuaries and tidal basins, because altered planform changes tidal dynamics and associated residual sediment transport. The morphodynamic response time to land reclamation is long, impacting the system for decades to centuries. Other human interventions (e.g., deepening of fairways or port construction) add a morphodynamic adaptation timescale to a system that may still adapt as the result of land reclamations. Our understanding of the cumulative effects of anthropogenic interference with estuaries is limited, because observations usually do not cover the complete morphological adaptation period. We aim to assess the impact of land reclamation works and other human interventions on an estuarine system by means of digital reconstructions of historical morphologies of the Ems Estuary over the past 500 years. Our analysis demonstrates that the intertidal-subtidal area ratio altered due to land reclamation works and that the ratio partly restored after land reclamation ended. The land reclamation works have led to the degeneration of an ebb- and flood channel system, transitioning the estuary from a multichannel to a single-channel system. We infer that the 20th-century intensification of channel dredging and re-alignment works accelerated rather than cause this development. The centennial-scale observations suggest that estuarine systems responding to land reclamations follow the evolutionary trajectory predicted by tidal asymmetry-based stability theory as they move towards a new equilibrium configuration with modified tidal flats and channels. Existing estuarine equilibrium theory, however, fails in linking multichannel stability to the loss of intertidal area, emphasizing the need for additional research.

Determination of biophysical properties of mangroves, e.g. tree height and diameter at breast height, is necessary for assessing mangrove ecosystem dynamics and growth. However, traditional surveying methods (e.g. diameter at breast height, location with GPS, and tree’s height with hypsometer) are time consuming and expensive. In this research we aim to assess mangrove properties by Unmanned Aerial Vehicles (or: UAV/drone) based photogrammetry. The additional benefit of this methodology is that mangrove environments which are often difficult to access can be reached. We focus on Porong Delta, Indonesia. In this area rapid delta progradation has taken place since 2006 due to an extreme mud volcano eruption. The regional climate conditions and added nutrient flux to the new delta have provided a suitable environment for growth of different mangrove species, such as Avicennia spp., Rhizophora spp., and Sonneratia spp. We used an off-the-shelve drone to generate a high-resolution spatial canopy height model (CHM) for the mangroves by using structure-from-motion (SfM) photogrammetry with an achieved DEM resolution of 5.2cm/pixel. This approach is used to determine the structural characteristics of mangrove stands and is validated with ground-truthing on two deltas. The dense point cloud derived from SfM photogrammetry is processed in LAStools and bare earth extraction with a Cloth Simulation Filter method. The CHM is generated from the processed point clouds. The structural information of mangroves is retrieved by using the lidR package in R. Our analysis lead to a median tree height on north and south delta of 4.2m and 3.5m, respectively. Analysis of photogrammetry data shows that drone-based observations of the mangrove canopy height are a useful tool to provide trustworthy data of mangroves characteristics.