Coastal Defenses
Table of Contents
Introduction
Coastal defenses can include hard or soft engineering solutions to help reduce the impact of flooding and sea level rise.
Why this is Important
Sea Level Rise "By 2100 in the USA, coastal population growth and sea level rise could put between 4 and 13 million people at risk of inundation"
Soft Engineering for Coastal Protection
Examples include coral reef restoration, oyster reef building and restoration, as well as other types of living shorelines.
Hard Engineering
These can include concrete or stone. They can be very effective, but they can also create dangerous conditions. In rivers, hard engineering can make conditions more dangerous for boats, swimmers, and wildlife.
Hard engineering solutions can also speed up erosion, creating serious destruction over time, or during major storm events. This in turn can result in higher long-term costs.
Some designers and scientists are exploring ways to combine hard solutions with biological components.
Soft Engineering
Living Shorelines
For centuries humans have destroyed natural coastlines in order to create hard coastline. However modern understanding of how the elements interact with these shows that we can boost biodiversity and soften nature's blows on our infrastructure when we opt for softer, living shoreline infrastructure.
Mangroves
These specialized forests full of salt-tolerant plants helps protects coastlines from erosion and storm intrusion slowing the destruction of coastal farmland and communities.
How Mangrove Forests Protect The Coast
12 second video of a tank demonstration showing how mangroves absorb and neutralize wave energy before it hits dry land.
Some places have been washed away so quickly after mangrove removal, that artificial barriers need to be build. Soon after soil has begun to rebuild, which may make mangrove replanting measures more likely to succeed.
Click the Mangrove button to learn more about mangroves or the Trees button to learn about free and affordable tree programs.
Mangroves
Oyster Reefs
These generally lie around the mouths of rivers and along coastlines. They help reduce the risk of flooding, and erosion from natural processes including extreme storm surges.
In addition to interrupting ocean forces on the shoreline itself, they also provide habitat and food for many species, which in turn provides economic benefits to local human communities.
Coral Reefs
These tend to lie farther out to sea, and help slow the impact of incoming waves and storms before they reach our shorelines.
Preserve Wetlands, Waterways, and Mangroves
Mangroves not only help prevent soil erosion, but help protect communities against hurricanes and other extreme weather. They have unique biodiversity, and serve many functions but are under threat from climate change, and human activities. Wetlands provide vital flood prevention with large spaces for overflow and absorption to take place. The vegetation both helps water sink into the soil and respirate back into the atmosphere. These wild areas also play a massive roll in preserving biodiversity for migrant and native species of fish, birds, and other wildlife. These in turn provide economic opportunities to the communities that preserve those ecosystems, while absorbing pollution so that it can do less harm.
Let Ghost Forests Turn to Salt Marsh
Communities will need to decide which areas they allow to become ghost forests and which will need to be protected by seawalls or other options. Communities may choose to allow ghost forests to turn into salt marshes, while picking new places for replacement trees to be planted. Strategic tree planting, especially along water ways can help recreate riparian buffers that will minimize erosion, sedimentation, pollution, and flooding higher in the watershed, which could allow for better protection along new coastlines.
Tree Planting
Establishing and protecting riparian borders can be a very powerful tool to protect water quality, mitigate flooding, control erosion, increase biodiversity, create wildlife corridors, protect ground water, and even improve water respiration to provide vital rain for crops.
Managed Retreat
Managed retreat can be paired with coastal defenses, as it may make sense for communities to spend money and other resources protecting culturally important locations, while sacrificing other locations for flood mitigation or coastal defenses. For example it may make sense to allow ghost forests to transform into wetlands, mangroves, oyster reefs, or even coral reefs depending on the expected sea level rise.
Buy Out Programs
These can help reduce inequity and make communities safer, as acquired land can be converted into spaces that bolster the overall community's safety against sea level rise and flooding.
Floating Buildings
Floating buildings have existed for a long time, but they can require more upkeep, and have various downsides, including risks from increasingly intense weather as climate change threats grow.
Hard Coastal Defenses
Man-Made Defenses
Wave Tank Demonstration Showing the Impact of Coastal Defenses on Flood Risk 12:22 minute video from the JBA Trust
Sea Walls
Methods
Install low-head dam for saltwater wedge and freshwater pool separation "Rising sea levels, combined with reductions in freshwater runoff due to drought, will cause the salt water-freshwater boundary to move further upstream in tidal estuaries. Upstream shifts of this boundary can reduce the water quality of surface water resources. Installation of low-head dams across tidal estuaries can prevent this upstream movement." -
Options to Boost Coastal Defense Effectiveness
Sustainable Drainage Systems (SUDS)
SUDs passively reduce flooding down stream by slowing the flow of water, letting it spread out in safe places so that it can better infiltrate the soil. This has many benefits from reducing erosion and siltation, to recharging ground water and making the landscape more resilient against droughts, fires and heatwaves.
Recharging ground water also means salt water intrusion can be reduced along coastal areas, while guaranteeing safe ground water for future generations.
Wetlands
Wetlands are natures sponges, and have been under threat from farmers and urban developers draining these natural resources. By restoring wetlands we both buffer land and communities from storms and floods, but we'll also restore biodiversity for millions of species who rely on wetlands to reproduce, eat, and find refuge year round or on their migration routes.
Wetlands
Buy Out Programs
These types of programs can be used to acquire space that can be used in coastal defenses. People are paid a fair price for land no one else would be wise to build, live, or work on, saving communities future rescue or rebuilding funds. Depending on the area, the purchased land can be used for community parks, mangroves or living shorelines, even seawalls depending on the communities' situation and needs.
Plant Based Shift
Altering Our Farming Priorities via Diet Shifts, Wiser Distribution of Farming Subsidies to Help Farmers Transition to Sustainable Alternatives Away from Those Causing the Most Water Stress and Pollution How we raise our food is deeply tied to water shortages, flooding, water pollution, and poor land management including deforestation and draining wetlands to create artificial grazing land can add significant, costly complications to these issues. With most of our land used to raise livestock which give a relatively tiny percentage of protein and calories in return, critically rethinking our dietary systems and land use practices could relieve significant amount of room to rehome people, grow enough food for our growing population, AND perhaps even return damaged land to the wild for better flood mitigation. Below are some key issues that can provide the most impactful returns at the least cost to consumers or policy makers.
Click the Plant Based button to learn more about switching to plant-based alternatives.
Return Land Drained for Grazing to it's Natural State
Reducing the consumption of animal products such as beef, wool, dairy, etc. will help reduce or even reverse our encroachment into wild places that traditionally acted as sponged for rain water. Some of these areas were actively pumped dry to allow grazing at the expense of valuable wetlands and forests, then over time compaction from animal hooves had mad many of these places suffer from increased erosion and soil compaction which stops water from penetrating. This means that fields can become prime causes of pollution and erosion, adding to flooding problems instead of working naturally as undisturbed wild places to do mitigate flooding.
Grazing uses the most land, is less efficient, meaning that "grass-fed" livestock take longer to reach slaughter-size while using more resources, and generally does not provide all of the benefits often touted by the livestock industry. For example carbon sequestration through well managed grazing, even in the best circumstances cannot reach a point of neutrality. The manure ends up directly on the ground where it can wash into water ways without any type of processing to reduce disease risk. Grazing is also the greatest cause of deforestation, which is problematic since trees are vital to water sequestration, fighting erosion, and reducing flood risk.
Ending subsidies to these operations would help prevent further destruction and expansion from this sector, while programs designed to support ranchers as they convert to plant-based agriculture will ensure that these people are supported in their time of need, while food and water security is ensured for everyone.
Click the Alternatives to Livestock button if you are a farmer who wants to find a more planet-friendly alternatives to raising animals or animal feed.
Click the Contact Your Representative button to tell your local leaders about this issue.
Combat Global Warming
Sea level rise is caused by increasingly warm global temperatures which are melting both our polar caps and our mountain ice. As our oceans warm, warm water expands, so this increases sea level rise even more.
The cheapest way to prevent sea level rise would have been to take climate change seriously several decades ago, but we're only now reaching a point where transitioning to green technology is finally taking off. We can speed the recovery of our planet if we continue pushing our energy use downward. Some effective and affordable solutions include
Increasing energy efficiency - this can include insulation and timer or motion sensor use
Saving excess energy, reusing, and recycling energies such as thermal waste into useable energy.
Switching to renewable energy use and production.
Tools & Apps
Water Pumping
The pumping of water takes a larger amount than many people realize. Pumping ground water for agricultural, industry, or public use, moving it between facilities, etc. all require energy since water is a fairly heavy substance.
STEEP "is a free Excel-based reference guide that can be used to make system assessments and identify potential areas for energy use savings in existing or planned water supply and wastewater facility projects."
Europe
UK
Southsea Coastal Scheme "is the UK's largest local authority-led coastal defences project, worth around £180M. It will stretch for 4.5km from Old Portsmouth to Eastney, and help to reduce the risk of flooding to more than 10,000 homes and 700 businesses. Approximately 4,000 of these properties are at risk of direct threshold inundation."
"The current defences are coming to the end of their lifespan, which increases the risk of flooding. We are creating new defences to embrace everything we all love about the seafront. The work will improve the seafront for future generations, while protecting the community and preserving the area's unique heritage."
Tools & Apps
North America
USA
USA Flood Factor Interactive map can be used to find specific addresses, and see how historical flooding as affected existing roads and neighborhoods. Please scroll down in page to find the partial US map, or type in an address and scroll down to find the interactive map.
Resources
Case Studies
Creating a Living Shoreline for Community Resilience (PDF) "AGU’s Thriving Earth Exchange helps American Venice preserve and persevere amid changing conditions"
Maps & Tools
Maps by Region Check specific State and Country pages to see if there are more specific maps, tools, projects, and groups for specific areas. If you have suggestions, we would love to hear what else we can include. Some states and countries have more detailed watershed, county, and city level maps. Other topic sections such as plastic, agriculture may be worth checking to understand how pollution enters our water ways, and how industries might endanger water sources without proper regulation, mitigation, or clean up systems to protect communities from these threats.
North America
USA
Disappearing Cities on US Coasts (Study) "The sea level along the US coastlines is projected to rise by 0.25–0.3 m by 2050, increasing the probability of more destructive flooding and inundation in major cities1,2,3. However, these impacts may be exacerbated by coastal subsidence—the sinking of coastal land areas4—a factor that is often underrepresented in coastal-management policies and long-term urban planning2,5. In this study, we combine high-resolution vertical land motion (that is, raising or lowering of land) and elevation datasets with projections of sea-level rise to quantify the potential inundated areas in 32 major US coastal cities. Here we show that, even when considering the current coastal-defence structures, further land area of between 1,006 and 1,389 km2 is threatened by relative sea-level rise by 2050, posing a threat to a population of 55,000–273,000 people and 31,000–171,000 properties. Our analysis shows that not accounting for spatially variable land subsidence within the cities may lead to inaccurate projections of expected exposure. These potential consequences show the scale of the adaptation challenge, which is not appreciated in most US coastal cities."
USA Flood Factor Interactive map can be used to find specific addresses, and see how historical flooding as affected existing roads and neighborhoods. Please scroll down in page to find the partial US map, or type in an address and scroll down to find the interactive map.
NOAA Flood Map Check specific State and Country pages to see if there are more specific maps, tools, projects, and groups in your area. If you have suggestions, we would love to hear what else we can include. Some states have watershed, county, and city level maps. Other sections such as plastic, agriculture may be worth checking to understand how pollution enters our water ways, and how industries might endanger water sources without proper regulation, mitigation, or clean up systems to protect communities from these threats.
USGS Ground Water Depletion in the United States 1900-2008 (PDF) understanding which area are suffering worst from ground water depletion can help us build better water management systems which could convert flood and rain waters back into aquifers. This would both ensure drinking and irrigations for future generations, as well as stabilizing soil which increasingly threatens building, road, and dam foundations in water-depleted regions.
Africa
Madagascar
The Wildfowl and Wetlands Trust " We conserve, restore and create wetlands, and inspire everyone to value the amazing things healthy wetlands can do for us." "Since 1960, over 60% of Madagascar’s wetlands are estimated to have been lost. Those remaining are subject to an array of pervasive threats including sedimentation, pollution and over-harvesting." "Lake Sofia is a Ramsar site – an accreditation given to the world’s most important wetlands through the intergovernmental Ramsar Convention. It is one of 21 Ramsar Sites in Madagascar. Few have Management Plans and conservation managers have little capacity to assess the condition of, and threats to, their sites. Currently, those involved in the conservation and management of wetlands work in isolation, and the lack of a functioning National Ramsar Committee for wetlands has resulted in missed opportunities to influence decisions around planning and regulatory frameworks that can have a significant impact on the health of these vital ecosystems."
Asia
Cambodia
Cambodian Rural Development Team
Department of Freshwater Wetland Conservation, Cambodian Ministry of Environment
NatureLife Cambodia
Europe
United Kingdom
The Wildfowl and Wetlands Trust "We conserve, restore and create wetlands, and inspire everyone to value the amazing things healthy wetlands can do for us." They work in multiple countries, but mostly the UK to preserve and rehabilitate wetlands as well as the water ways that feed them. Projects include
North America
USA
Anthropocene Alliance (A2) "has almost 300 member-communities in 41 U.S. states and territories. They are impacted by flooding, toxic waste, wildfires, and drought and heat — all compounded by reckless development and climate change. The consequence is broken lives and a ravaged environment.
The goal of A2 is to help communities fight back. We do that by providing them organizing support, scientific and technical guidance, and better access to foundation and government funding. Most of all, our work consists of listening to our frontline leaders. Their experience, research, and solidarity guide everything we do, and offer a path toward environmental and social justice.
Supported by outstanding partner organizations with expertise in engineering, hydrology, public health, planning, and the law, A2 leaders have successfully halted developments in climate-vulnerable areas; implemented nature-based hazard mitigation strategies; organized home buyouts; and pushed for clean-ups at superfund sites, toxic landfills, and petrochemical plants.
We support everyone we can, but our special priority is people who have suffered the worst environmental impacts for the longest time; that usually means low-income, Black, Latinx, Native American and other underserved communities.
To learn about our policies, read our A 10-Point Platform on Climate Change."
Grants & Funding
Asia
Livable Cities: Financing Partnership Facility "The urban operations of ADB benefits from the support of notable trust funds, which are collectively referred to as the Urban Financing Partnership Facility. Under this umbrella, strategic, long-term, multi-partner investments on innovative urban solutions are implemented. These investments help to achieve the vision of livable cities." These include:
Urban Climate Change Resilience Trust Fund (UCCRTF) eligible countries include Bangladesh, India, Indonesia, Myanmar, Nepal, Pakistan, Philippines, and Vietnam.