Natural Defense Projects

What is the Natural Defense Projects app?

icon_activeThe Natural Defense Projects App evaluates natural coastal habitats like reefs, mangroves, and marshes that often play an important role in coastal protection.

As there is growing evidence to show that these natural defenses can be as or even more effective than hard engineering in some situations, the database allows users to explore a comprehensive global summary of natural defense projects across multiple habitat types. It includes a brief description of the roles and effectiveness of each habitat’s coastal protection abilities. The database is part of the ongoing SNAP Coastal Defense project that explores how coastal habitats may be managed to help protect communities from the impact of extreme environmental events.

Main functions:

  • The database maps 67 examples of natural coastal defenses around the globe to help demonstrate that: a) coastal habitats can and do provide considerable coastal protection; and, more importantly, b) we actually do know quite a bit about where, when, how and how well specific habitats work as coastal defenses. In addition to mapping, the database also summarizes information on the coastal defense characteristics of each example.
  •  You can sort the projects by habitat type (e.g., mangrove, coral reef), exposure and several other factors. Additional information is also provided for each case study indicating its effectiveness and cost-benefit analysis. Users can therefore easily pull up information on projects that fit specific habitat and site criteria such as mangrove projects in high exposure regions, or salt-marsh projects along estuarine coastal systems, and more.


Who should use it?
  • Managers of Coastal Protection Infrastructure
  • County Planners & Managers
How does it work?

The 67 examples shown here are the results of a search for demonstration and restoration studies with enough data for further (on-going) synthetic and meta-analyses. While there are more projects than covered currently in the database, the focus is on studies where the methods and effectiveness are well documented.

Meta-analyses of the studies, among five habitats (coral reefs, mangroves, salt-marshes, seagrass/kelp beds), show that these habitats reduce wave heights significantly and this reduction varies with the habitat and the site.

Across all habitats, coral reefs emerge as having the greatest potential for coastal protection: they are highly effective at reducing wave heights and are also exposed to higher, more powerful waves. Salt-marshes are almost as effective in terms of wave reduction but occur in more sheltered environments. Mangroves and seagrass / kelp beds are about half as effective, with mangroves occurring in the most sheltered environments.

There is also a strong positive, linear correlation between the extent of reductions in wave height, and the wave height before the habitat, in the order coral reefs > salt-marshes ~ mangroves > seagrass / kelp beds.

What are the strengths and limitations?

App Strengths

  1. The app provides a snap shot as well as supporting project information for a wide array of natural defense projects across the globe.
  2. The user is able to sort through the projects according to the habitat type, coastal classification, level of exposure, and project objective to learn more about specific projects.

App Limitations

  1. While the examples in the database are extensive, they are not exhaustive.
  2. For instance, projects on beaches and dunes have not yet been incorporated, but will be in phase 2 of the project. More information on site conditions such as exposure to storms and risk characteristics, such as sea-level rise values, will also be added.