Module 8: Managed Retreat/Multi-Layered Protection
In Module 8, Managed Retreat/Multi-Layered Protection, we look at some of the alternatives to rebuilding in place while strengthening the flood defenses with larger and stronger structures. We consider the concepts of managed retreat, moving entire communities, and alternate rebuilding methods to produce more resilient coastal communities. The goal is to introduce students to the idea of relocation of human landscapes in coastal environments due to repeated impacts from coastal hazards, and to continue to examine the rebuild versus retreat debate. By the end of the module students will:
- Investigate alternative methods for non-structural shoreline hazard mitigation, including managed retreat and multi-layered defenses.
- Explore the pros and cons, including cost-benefits of managed retreat case studies and consider examples of communities facing retreat as an option and the factors leading to these decisions.
- Analyze hypothetical storm surge impacts on communities on the Louisiana coast, from Google Earth and online tools.
- Formulate detailed recommendations for the future of a coastal community, using real examples from the Louisiana coast.
Context for Use
Description and Teaching Materials
In Module 8 the students consider cases in which communities are opting to retreat from shorelines impacted by repeated coastal hazards. They explore, through a variety of reading materials, examples of approaches to managed retreat found around the world. In the formative assessment the students use Google Earth to make measurements of the low-profile Louisiana coast to consider the question of retreat by a community that is experiencing repeated flooding from the Gulf of Mexico. They take these measurements and apply them in a 1-D model accessed online to measure the height of storm surge under varying scenarios. The summative assessment asks the students to put themselves in the shoes of coastal managers who must make decisions about the future of this community. The students write their recommendations from two viewpoints. Materials for students for this module are located at the link below. Teachers can find documentation of the activities at this location as well as rubrics for students. Rubrics for teachers are compiled under Assessment on this site. Suggestions for teaching and a list of the assessments are found below.
Teaching Notes and Tips
The students first work through a series of U.S. and overseas examples to consider a variety of approaches to coastal hazard mitigation, including managed retreat, multi-layered defenses, as well as relocation "buyout" programs and other scenarios. They then work through a case study on the Louisiana coast that illustrates the situation of a community located on a very low-profile coastline that is projected to become more vulnerable to storm surges due to ongoing subsidence and sea-level rise. The formative and summative assessments are based on this case study.
Reflections on Assignments
Formative Assessment exercise:
A case study of the town of Isle de Jean Charles is revisited (first introduced in Module 6). This case is used as a basis of an exercise to make measurements to determine the impact of storm surge on this community. After the bed slope is measured, a 1-D model is used to run scenarios of varying wave heights and wind speeds to measure the storm surge at Isle de Jean Charles and consider the impact on the community.
The students write a response to two role-play situations. One considers the role of a coastal restoration specialist "leader" and asks them to write recommendations to the state Coastal Protection and Restoration Authority for the future of Isle de Jean Charles. The other considers the role of a scientist on a panel who makes a speech that presents recommendations for the residents for the future of the town.
What works best for the module:
The formative assessment investigation of the Louisiana coast case study worked well. Students responded well to the case study and the work was at the right level.
Students should be encouraged to work through and thoroughly read the materials at the beginning of the module that introduce the various methods of coastal hazard mitigation. Students who read all of the material and follow the extra, external links will develop the most complete understanding of concepts. Numerous concepts are embedded in the links that will foster a richer understanding of assessment topics, and students should be encouraged to investigate these materials.
What students found tough and how we adapted:
Students who did not thoroughly read the text and look at the accompanying external links had the most problems with the module. These students were unable to relate concepts to one another and consequently had difficulties completing some of the assessments.
The summative assessment was challenging for the students.
Recommendation: The students can choose between the two "roles" for the summative assessment. They can choose to either write a recommendation to the state as a coastal community leader or write a speech to be presented by a scientist on a panel to be presented to coastal community leaders and residents.
1. Imagine you are a leader in coastal restoration and you manage a limited budget to spend on this small part of the Louisiana coast. Outline the recommendations you would present to the Coastal Protection and Restoration Authority for protecting this community. Justify all of your points with facts from the above exercises.
1. Imagine you are on a panel of scientists making recommendations to the community in a world in which budgets are tight and there are many competing needs for the resources available. Write a speech with recommendations for the future to be presented at a local public meeting at which the residents of Isle de Jean Charles will learn about the fate of their town.
- Formative Assessment: Louisiana Coastal Flooding: Students analyze hypothetical storm surge impacts on communities on the Louisiana coast from Google Earth and online tools.
- Summative Assessment: Recommendations for the Louisiana coast: Students formulate detailed recommendations for the future of a coastal community, using real examples from the Louisiana coast.
References and Resources
- Student readings are provided in Student Materials — Module 8: Managed Retreat/Multi-Layered Protection
- We need to retreat from the Beach, a New York Times article by Orrin H. Pilkey
- Rebuild or Retreat from the Jersey Shore , by Janet Babin, published by WNYC News
- Managed Retreat Strategies — Case Studies
- Restoration and Managed Retreat of Pacifica State Beach, by Jessi Kershner, published on CAKE.
- Let it Flood: One English Town's Innovative Response To Sea Level Rise , by Joanna M. Foster, published on ThinkProgress.org
- Managed realignment of sea walls can enhance coastal protection provided by natural habitats and save costs , compiled by: Johannes Förster and Lucas De Muelenaere, mainly based on Turner et al. 2007 and DEFRA and EA 2002