It is not an uncommon sight to see flooding from storm surges and high tides in some low-lying communities on the Eastern Shore of Maryland. With rising tidal ranges and threats of flooding from more intense storms, coastal communities are having to face harsh realities and decide on potential solutions to encroaching seas.
University of Maryland Center for Environmental Science Professor Ming Li’s research focuses on the threats coastal communities face and potential solutions to the rising tides, as the impacts of climate change grow.
Li’s work focuses on a myriad of estuarine and coastal dynamics, including numerical ocean modeling, regional impacts of climate change, sea-level rise and coastal flooding, causes of hypoxia, harmful algal blooms, and ocean acidification. With all of this experience he works on UMCES’ Sea-Level Rise Projections for Maryland, a publication released every five years for the the State of Maryland. He also leads the Estuarine Coastlines and People (CoPe) Research Coordination Network, a group of national experts focused on understanding the dangers coastal communities face and the impacts of a changing coastal environment.
“Sea-level rise and intensifying storms in a changing climate are a global phenomenon, but sea levels in a bay or estuary depend on how we manage coastlines,” said Ming Li.
Climate change and its effects is a complex issue where communities are not only trying to mitigate the source of the problem but also must find the best solutions to deal with the effects they are seeing in present day.
While sea levels are rising, the rate at which they are rising is also increasing, which means more water, sooner. Global average sea level change has risen over 20 centimeters, about 8 inches, since the 1900s. While it may not seem like much, low-lying coastal communities are threatened by the cyclical high tides and storm surges flooding roads and infrastructure. Rising tides means higher high tides, and the resulting flooding is affecting people’s day-to-day lives by impacting roads and infrastructure, both in rural areas like Crisfield and Dorchester County on the Eastern Shore and urban areas, such as downtown Baltimore and Annapolis.
The Chesapeake Bay region, with 11,684 miles of shoreline, is highly vulnerable to sea-level rise.
“We see a long-term upward trend of sea level rising 3 to 5 millimeters per year, which is double the rate sea level is rising globally, mostly due to the land subsidence in the southern Mid-Atlantic region,” said Li
Sea-level and the rate at which it is rising are not the only things increasing. The warming rate is also on its way up, which could lead to more complex environmental consequences.
In addition to high tide flooding, hurricanes and tropical storms can also cause problematic flooding. In 2020, there was a particularly intense hurricane season in the Atlantic, which experts seem to think is going to be the new normal as we continue to see the effects of climate change.
“Although the number of storms varied from year to year, the number of major category four and five hurricanes has increased in recent decades, and human factors has contributed to this storm intensification, “ said Li.
According to the World Meteorological Organization and the International Panel on Climate Change (IPCC), an index used to measure total hurricane power over a hurricane season, called the Power Dissipation Index (PDI) has gone up. The index combines storm frequency, duration, and intensity to understand the threat of storms each year—and there has been a clear increase since the 1980s. The higher PDI shown in recent years exhibits the detectible increase in the global average intensity of hurricanes, global proportion of storms reaching category four or five, and extreme precipitation events.
The threat from hurricanes not only comes with higher Power Dissipation Index, but stronger storms draw up more water. Coastal cities will be not only threatened by stronger storm surge but also by heavy precipitation, potentially causing catastrophic and historic flooding for communities.
“Sea-level rise and stronger storms will lead to more extensive flooding over coastal regions. For example, Hurricane Isabel (2003) generated a peak water level of 6-7 feet in downtown Baltimore. A similar storm in 2100 could generate a peak sea level of almost 9 feet in Baltimore if low-lying areas are allowed to be flooded but 12 feet in Baltimore if sea walls or levees are placed to protect the low-lying areas,” said Li
The damages from storm surge are not only physical, but may have an increased economic impact as property value decreases because of increased risk.
Ming Li uses an interesting analogy to discuss the different methods coastal communities can attack climate change. He references war strategies to explain the different methods of coastline management. Are you going to defend the front line or occupy the higher grounds?
The solutions to protect coastlines come at a significant cost. With solutions ranging from engineering sea walls to nature-based systems, such as wetland restoration and oyster reefs, there are a variety of options with varying challenges and benefits. Regions like Baltimore’s Inner Harbor might need different solutions to protect its infrastructure from coastal flooding than a rural community on the Eastern Shore.
“There is no one solution that will fit all the bills. We should try different approaches in different areas depending on the needs of each region,” said Li.
While no one solution will fit all the bills, the cost of these solutions racks up quite a bill. Projects to protect shorelines come at a hefty, but necessary cost, potentially billions of dollars.
Nature-based solutions such as creating wetlands, planting seagrass or oyster reef restoration can be comparable or lower cost than engineered structures, such as sea walls or levees, while providing the co-benefits of ecosystem services. Storm barriers, a type of floodgate used to prevent storm surge and rising tides, are another option, but they can have detrimental impacts on altering natural tides, including the possibility of worse salt water intrusion onto coastal ecosystems and worse hypoxia, water quality and algal blooms.
The alternative? Occupy higher grounds using planned relocation.
The idea of moving entire communities away from regions where they have resided for decades is not an easy one to consider. Not only is there the monetary cost of moving communities but the loss of community, heritage, and history makes it a difficult decision to make.
“Low-income or minority communities are often located in these vulnerable regions being considered for managed retreat. We need to carefully consider the social justice implications of potential buyout programs to relocate these populations to higher ground,’ said Li.
The solution to protect encroaching coastlines is already being considered in places like Isle de Jean Charles in Louisiana. It had 300 houses in 1950 but has lost 98% of land due to sea-level rise. Federal funding allowed residents of this community to relocate to higher ground.
“Looking to the future, yes, there are uncertainties in how emissions scenarios will change and different climate change scenarios, but these projections come with a certainty range where we know we will be seeing effects of climate change,” said Li.
In order to fight the surging seas affecting all regions of the Chesapeake Bay community, communication and collaboration between regions and communities is essential, said Li. Solutions imposed in one region can affect the solutions another region may want or need to implement.
“By working together, coastal communities around the Chesapeake Bay can come up with the most cost-effective and most equitable strategy to tame the rising seas,” said Li