Wave height (regular and irregular waves) reduction in 2m water depth over a 40-m-long salt marsh test section in a large scale laboratory flume

Coastal communities around the world face increasing risk from flooding as a result of rising sea level, increasing storminess, and land subsidence. Salt marshes can act as natural buffer zones, providing protection from waves during storms. However, the effectiveness of marshes in protecting the coastline during extreme events when water levels and waves are highest is poorly understood. Here, we experimentally assess wave dissipation under storm surge conditions in a 300-m-long wave flume that contains a transplanted section of natural salt marsh. We find that the presence of marsh vegetation causes considerable wave attenuation, even when water levels and waves are high. From a comparison with experiments without vegetation, we estimate that up to 60% of observed wave reduction is attributed to vegetation. We also find that although waves progressively flatten and break vegetation stems and thereby reduce dissipation, the marsh substrate remained remarkably stable and resistant to surface erosion under all conditions.The effectiveness of storm wave dissipation and the resilience of tidal marshes even at extreme conditions suggest that salt marsh ecosystems can be a valuable component of coastal protection schemes.

Tab 1-4 Weight and volume reduction as well as surface subsidence during abrasion experiments

Antarctic land surfaces in South Victoria Land, all without a covering of vegetation, are actively formed by winds which often reach velocities of more than 100 km/h. Consequently, deflation and abrasion are essential factors in the process of slope formation. Water erosion, active only during the very short summer period, is limited to a few localities in South Victoria Land. Experiments in a wind tunnel proved that ventifacts in the Dry Valleys can be formed within a few decades or at the most, a few centuries. Yearly corrasion rates average around a maximum of a few millimeters. Considerable variability is caused by the different exposures of ventifacts within the micro relief end the varying resistance of the rocks. The importance of ice crystals (snow) for abrasion processes should not be overestimated.