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The world’s population continues to grow, and at the same time, the oceans are rising, posing challenges for those living near coastal areas. Almost two-thirds of the global population resides within 50 kilometers of the coast. Mangrove forests offer solutions to mitigate the potential for flooding and provide natural coastal protection. Traditionally, mangrove restoration has been approached from the seaward edge through large-scale planting, with limited success. This dissertation describes how mangrove restoration can be approached from both the seaward and landward edges along degraded coastlines to create functional mangrove forests. Chapter 2 examines how the natural factors drive mangrove dynamics along the landward and seaward edges of a mangrove greenbelt. This work reveals that landward mangrove expansion in old aquaculture ponds was slow because of long inundation times and soft sediment. In contrast, seaward mangrove expansion was associated with elevated mudflats and gentle slopes. Chapter 3 further investigates the effects of different foreshore morphologies on mangrove expansion. This work shows that cheniers, or elevated sand lenses atop muddy foreshores, significantly decrease waves that enter the mangrove fringe. A stable chenier can promote mangrove expansion, even in combination with a negligible small mudflat of 10 to 20 metres. Without a chenier, a 10 times wider mudflat was required to make mangrove expansion more likely than mangrove retreat. Chapter 4 compares traditional mangrove planting with ecological restoration measures for mangrove restoration (EMR). This work shows that EMR measures were more effective at creating connected forest expansion in a landward direction. EMR in the landward direction could be achieved through smart sluice gate management in the right season. This work shows how mangrove cover in associated mangrove aquaculture ponds significantly increased over the project lifetime. Along the seaward edge, field experiment

To shed light on the future of low-lying rural areas in the face of sea level rise, we studied a 20 km long rural coastline neighbouring a sinking city in Indonesia (8 – 20 cm yr-1), hereafter called studyarea. Through the collection of data across 7 main topics, we show that villages experienced significant RSLR near the city. Mangroves also experienced RSLR near the city, although to a lesser degree, and were able to respond to RSLR rates 4.3 cm yr-1 through various root adaptations. The seven main investigated topics, and their respective datasets: 0. village population migration1. village house experienced RSLR2. mangrove experienced RSLR2a. mangrove experienced RSLR2b. rainfall data3. foreshore dynamics4. mangrove bed-level dynamics based on pneumatophore markings5. mangrove root acclimation5.1. pneumatophore markings (same dataset as 4.)5.2. rootmat formation5.3. sedimentation experiment6. lateral mangrove die-back6.1. dead trees and summary of all datasets as used in Figure 4 of the manuscript6.2. pneumatophore mortality (same dataset as 4.), To shed light on the future of low-lying rural areas in the face of sea level rise, we studied a 20 km long rural coastline neighbouring a sinking city in Indonesia (8 – 20 cm yr-1), hereafter called studyarea. Through the collection of data across 7 main topics, we show that villages experienced significant RSLR near the city. Mangroves also experienced RSLR near the city, although to a lesser degree, and were able to respond to RSLR rates 4.3 cm yr-1 through various root adaptations. The seven main investigated topics, and their respective datasets: 0. village population migration1. village house experienced RSLR2. mangrove experienced RSLR2a. mangrove experienced RSLR2b. rainfall data3. foreshore dynamics4. mangrove bed-level dynamics based on pneumatophore markings5. mangrove root acclimation5.1. pneumatophore markings (same dataset as 4.)5.2. rootmat formation5.3. sedimentation experiment6. lateral mangrove die-back6.1. dead trees and summary of all datasets as used in Figure 4 of the manuscript6.2. pneumatophore mortality (same dataset as 4.)

The hydro-and morphodynamic processes within the Vietnamese Mekong Delta are heavily impacted by human activity, which in turn affects the livelihood of millions of people. The main drivers that could impact future developments within the delta are local stressors like hydropower development and sand mining, but also global challenges like climate change and relative sea level rise. Within this study, a hydro-morphodynamic model was developed, which focused on a stretch of the Tien River and was nested into a well-calibrated model of the delta's hydrodynamics. Multiple scenarios were developed in order to assess the projected impacts of the different drivers on the river's morphodynamics. Simulations were carried out for a baseline scenario (2000-2010) and for a set of plausible scenarios for a future period (2050-2060). The results for the baseline scenario indicate that the Tien River is already subject to substantial erosion under present-day conditions. For the future period, hydropower development has the highest impact on the local erosion and deposition budget, thus amplifying erosional processes, followed by an increase in sand mining activity and climate change-related variations in discharge. The results also indicate that relative sea level rise only has a minimal impact on the local morphodynamics of this river stretch, while erosional tendencies are slowed by a complete prohibition of sand mining activity. In the future, an unfavourable combination of drivers could increase the local imbalance between erosion and deposition by up to 89%, while the bed level could be incised by an additional 146%. © 2020 by the authors.

Relative sea level rise (RSLR), that has been occurred along the entire coastal areas of the Northern Adriatic Sea, includes land subsidence, both natural and man-induced, and eustacy. Their combined effect has produced relative ground settlements ranging from centimetres to meters. RSLR represents one of the geologic hazards threatening the low-lying coast. Recent progresses made in understanding these two processes are presented. Synthetic Aperture Radar (SAR) interferometry has significantly improved the knowledge of actual land subsidence. In particular, comprehensive maps of the vertical displacements occurred over the period 1992-2009 in the region between Venice and Ravenna reveal a significant spatial variability, ranging from a slight 1 to 2 mm•yr-1 uplift, to a serious subsidence of more than 15 mm•yr-1. The availability of tide gauge data in Trieste, Venice, and Ravenna allows accurate assessment and meaningful observations on sea level change. The period 1896-2006 is characterized by an average rise of 1.2±0.1 mm•yr-1. The analyses here performed show that a time series at least 50 yr long must be used to obtain statistically significant results and reliable trend, due to the 7-8 year pseudo-cyclicity, recorded at many Mediterranean coastal stations. In Venice and Ravenna the influence of land subsidence on the RSLR amounts to 57% and 85%, respectively. This percentage has been estimated in 95% at the Po Delta.