heart rate and blood pressure (Cracknell et al. 2018), and exercising outdoors has greater psychological benefits than the same level of physical activity indoors (Depledge and Bird 2009). Water features appear to be particularly restorative, with access to coastal areas reducing stress, increasing physical activity, and resulting in stronger communities (Depledge and Bird 2009). NNBF can improve the health of communities that they protect. Flood storage areas with park-like features, such as recreation fields and walking trails, encourage physical activity and store water during rain or flood events. Coastal dunes provide protection from storm surges or high winds, while also providing materials for beaches as they evolve and shift (Casarin et al. 2012) and supporting a variety of outdoor recreation activities.
Water quality and sediment supply The functions of NNBF that help reduce flooding and erosion also provide mechanisms for sediment processes that result in improvement of water quality. For example, reconnection of wetlands, including floodplain forests and intertidal marshes, can be effective in managing high nutrient loads and increases in sediment deposition inland, thus reducing downstream sediment loadings. Water quality benefits can also flow from nearshore NNBF. For example, oysters are suspension feeders that feed on particulate organic matter, such as detritus and phytoplankton. By pulling these particulates out of the water column, oyster reefs can improve light availability for other ecosystems (e.g., seagrass in Chesapeake Bay) and water quality for people and fish.
6.2.3 The Costs of NNBF All interventions and structural measures, both hybrid and NNBF, involve analyzing costs and trade-offs throughout the project life cycle. For NNBF to be considered as alternatives to, or in combination with, structural measures such as seawalls, bulkheads, and levees, it is necessary to also analyze their costs and potential trade-offs. The following are the main costs in the total life cycle of a typical NNBF project (adapted from Bilkovic et al. 2016): • Planning costs • Design and permitting costs • Costs of the land (or space) required for the project, including opportunity costs • Costs of creation, protection, or restoration • Costs of maintenance and monitoring The cost of land may be a major component of these costs for some NNBF, especially in urban areas and narrow coastal margins. After cost of land, the other key components of NNBF costs are design, permitting, creation, protection, and restoration. However, an advantage of well-designed NNBF is the ability to “self-maintain” using natural processes—for example, by retaining soil and keeping pace with sea-level rise (Temmerman and Kirwan 2015), which can significantly reduce long-term maintenance costs and the need for infrastructure upgrades. In some contexts, NNBF can be more cost-effective than structural measures due to the limited maintenance cost. The costs of creation are highly variable, depending in part on geographic location, type of NNBF, and intervention (e.g., restoration through planting versus hydrological intervention).
06 | Benefits and Costs of NNBF
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