Coastal areas are frequently impacted by severe storms, resulting in extreme damages to society and infrastructure. Moreover, this risk is expected to increase under rising sea levels, climate change and increased land development. In this dissertation, two main goals are defined to support coastal resilience and protection against this threat: 1) improve our ability to simulate coastal hazards in the Chesapeake Bay; and 2) explore the effectiveness of natural defenses, such as saltmarshes, in attenuating coastal hazards (storm surge and waves). Firstly, the widely used numerical system ADCIRC+SWAN was applied to explore the importance of numerical parameters, physical processes and atmospheric forcing when implementing hydrodynamic models in estuarine environments to simulate coastal hazards regionally. Secondly, numerical modeling and a 3-year field-based monitoring campaign documenting water levels, wave parameters and currents were used to evaluate the ability of coastal ecosystems to mitigate floods and attenuate waves. The analysis of measurements collected in two saltmarshes in the Chesapeake Bay during several Hurricanes, Nor'easters and other coastal storms demonstrated that 200--400m marshlands can be a viable option for coastal protection against waves, although they would be less efficient to mitigate high water depths from storm surge. Furthermore, field-based analytical formulations to predict wave height decay within the marsh were derived and validated using different events. In addition, local scale numerical model (X-Beach) simulations demonstrated that these predictive formulations can properly replicate the wave height decay within other marshes of the Chesapeake Bay. This study advances the scientific knowledge of the coastal protection capacity of saltmarshes and provides reliable numerical tools that can be used by coastal engineers to support decision makers for adopting natural and nature-based coastal defenses.