Global mean sea level is both rising and accelerating. By the year 2100, it is predicted to rise by 0.61–1.10 m under the business-as-usual climate change scenario according to the latest IPCC report. This estimate is likely to increase as that deadline looms closer, as scientists discover more compounding effects of climate change.
Although melting glaciers and disappearing ice sheets play a role in sea level rise (each accounts for 25% of increased volume), the other and potentially unexpected reason for the shift is thermal expansion (accounts for the other 50%). Thermal expansion states that as water heats up, there is more distance between the particles and the liquid will take up more space. Warmer oceans will contribute to sea level rise because of thermal expansion. Being the crafty creatures that we are, humans have created ways to adjust to sea level rise, increasingly frequent severe storms, and other coastal issues such as erosion. Here, I discuss one such technique and why better adaptation strategies are crucial.
The two types of coastal engineering styles are hard and soft engineering. Hard engineering uses incorporates a lot of technology, substantial investment, and human-based solutions, while soft engineering is based on minimal technology, limited funds, and nature-based solutions with better long-term feasibility. Sea walls are an example of a hard engineering solution. An example of a soft engineering solution would be coastal wetland restoration. Fortifying coasts with salt marshes, mangroves, and tidal estuaries provides a buffer that will break up waves before they reach the coast, lessening erosion and flooding.
Models must be used to determine where to place sea walls, which are enormous, expensive, and obstructive. Standard sea walls are prone to structural damage because the waves continuously crash straight into the base of the structure and thus, they require regular maintenance. More advanced sea wall structures feature a curved shape that returns the force of the waves back to sea, which breaks them up and reduces pressure on the wall.
Sea level rise is not the same at all locations along the coast. While some cities such as Chesapeake Bay are facing higher than average rising sea levels (+5.92 mm per year), other cities such as Crescent City in California are not witnessing the same changes (-0.78 mm per year due to local tectonic activity). This information is listed in a detailed report released in the summer of 2019 by the Center for Climate Integrity in their sea level rise cost study, in which they performed calculations based on a proactive climate change scenario with a 1-year storm surge. For comparison, Hurricane Sandy was a 103 to 260-year storm, so the estimates in the Center for Climate Integrity report should be considered conservative. This article is helpful in explaining the differences between the different carbon dioxide emissions scenarios created by IPCC.
Florida will face the largest costs of coastal protection at around $76 billion by 2040. Louisiana will follow with the second largest costs at $38 billion, then North Carolina, Virginia, and Maryland. Individual counties and cities will face financial crises as well. Cities that will incur costs greater than $1 billion include Jacksonville FL, New York City, Virginia Beach VA, Marathon FL, Fire Island NY, Galveston TX, and Charleston SC.
New York City’s Staten Island has already pledged funds to build a massive 5.3 mile, twenty foot tall buried sea wall to protect against a 300-year flood. Of course, sea walls aren’t the only form of coastal engineering available. Some alternatives that serve the same purpose are: gabions (bunches of rock held together by mesh), breakwaters (walls that are farther out to sea), dune restoration, and beach stabilization (widening the beach to absorb wave impact).
Through my research, I have been looking closely at wetland restoration as a management technique. Unfortunately, the sea walls that are so crucial to protecting developed coastlines prevent natural migration of coastal wetlands. Coastal wetlands tend to migrate in different directions (seaward, landward, driftward, etc.). Sea walls prevent this migration and thus the natural “soft engineering” technique of wetland restoration becomes less likely as coastal wetlands continue to face challenges.
Do you live near a coastline? (Hint: The Great Lakes are considered coasts!) What coastal engineering technique does your city employ? Are there houses and buildings right up against the coast? Share your thoughts below 🙂