PIs: Xiaoxia Zhang and Heidi Nepf
Coastal marshes diminish the impact of coastal storms and waves and when given the right conditions can grow along with sea-level rise. During Hurricane Sandy, coastal marshes reduced flood damage by $625 Million1. Marshes also provide additional benefits, such as protecting coastal water quality and providing habitat. In 2015 the US Office of Management and Budget directed federal agencies to incorporate restoration and management of vegetated landscape [aka green infrastructure] in coastal planning. However, these efforts are stymied by a lack of modeling tools to quantify the functions of green infrastructure. In particular, salt marshes are efficient in dissipating wave energy. This study developed models that predict wave dissipation by marsh plants, which can be used to assess the level of coastal protection provided by a marsh. Most marsh plants are composed of flexible leaves and a comparatively more rigid stem. The flexibility allows for reconfiguration under hydrodynamic force, which reduces the plant drag. Unlike previous models, the new model accounts for both plant morphology and flexibility.
Read the article in MIT News.
Also featured in APS-Physics News
PIs: Isabella Schalko and Heidi Nepf
Over the past century, rivers have been degraded by land-use change and flood management, resulting in poor habitat and diminished nutrient retention. Now, resource managers use large wood pieces to restore habitat and natural river function. To plan and evaluate these river restoration projects, it is important to understand the interactions between flow, wood, and sediment. The goals of this project were to quantify flow and morphological structures associated with different wood accumulation setups. The results will be used to develop design recommendations for wood accumulations.
Read the article in MIT News
Designing Stormwater Detention Ponds and Wetlands for Urban Areas
PIs: Celina Guzman, Alan Berger, and Heidi Nepf
This project combined hydraulic engineering and landscape design to create new landscape forms for stormwater detention ponds and constructed wetlands that improve storm water management while also providing ecological benefits and versatile green space for cities. The designs, which feature a series of clustered islands, are modular and scalable, so they can be tailored to fit the needs and resources of varying urban settings.
Read the Design Guideline
Read the article in The Dirt, hosted by American Society of Landscape architects
Floating Treatment Wetlands for Storm Water Treatment
Manoel Xavier and Dr. Johannes Gerzen
Constructed wetlands using rooted plants have been integrated into water treatment, providing habitat and recreational value in addition to their water treatment function. This green infrastructure is harder to implement for storm water detention ponds and river channels, because variation in water level makes it difficult for rooted vegetation to establish and survive. Floating treatment islands (FTI) provide an alternative for water treatment, because the floating vegetation can tolerate the swings in water depth. FTIs consist of emergent vegetation grown hydroponically on a floating structure. The roots extend down into the water, providing a substrate for biofilm growth. The treatment provided by an FTI depends on both the volumetric extent of the root zone, as well as the contact time between the root zone and the polluted water. A better understanding of the circulation of water through the root zone, and its dependence on FTI size and position can provide important guidance to the design of these systems. This study used computational fluid dynamics to characterize root contact time and to betterunderstand the impact of FTW configuration on the nutrient removal efficiency of a FTW system.
Funded by the Abdul Latif Jameel World Water and Food Security Lab