C. Reid Nichols

Coastal Morphodynamics and Ecosystem Dynamics

The shape of the land and the processes that mold the land are mutually interconnected and change together as a complex system. The coupled suites of mutually-inter-dependent hydrodynamic, biologic and anthropogenic processes, seafloor and landscape morphologies interact to cause time-dependent sequences of change. In many cases it is moving water or air (currents, waves, winds) that redistribute the material. The new land configurations in turn then alter the directions, intensities and gradients of the moving water or air. In other cases, it is biological rather than physical processes that build or degrade morphologic features such as coral reefs or coastal marshes. There is constant feedback among the multiple components of the system.

Mid Atlantic Bight and Chesapeake Bay

The Mid-Atlantic Bight (MAB) extends alongshore, from Cape Cod, MA to Cape Hatteras, NC and includes major estuarine systems such as Narragansett Bay, Long Island Sound, Chesapeake Bay and Pamlico Sound. Sea level rise continues to have a dramatic effect on developed watersheds and urban estuaries, which are common to this highly populated region. Tropical cyclones contribute to flooding, which impacts coastal roads, homes, farms, and even fresh water supplies. Research is being applied to improve our understanding of the physical processes that connect estuaries and the coastal ocean and better forecast floods. Advances will result in improved marine policies and coastal resilience.

Sea Level Rise: Recent Trends and Future Projections

Seas are rising and seriously impacting coasts and coastal communities globally. Global warming is causing melting of glaciers and steric expansion of water volume. Locally and regionally, other effects including land subsidence and the slowing of ocean currents such as the Gulf Stream are causing additional rises. By midcentury, relative sea levels in cities like New York and Miami may exceed those of the year 2000 by up to 1.2 m (~ 4 ft.).

Complex Intersections of Seas, Lands, Rivers and People

River deltas were the cradles of early civilizations and are currently the habitats of 500 million people. But river deltas worldwide are sinking and being invaded by rising seas. The effects of sea level rise and floods are greatly exacerbated by subsidence and human modifications including reductions in supply of sediment and the extraction of water, oil and gas from deltaic sediments as well as damaging engineering works.

Coastal Systems in the Anthropocene

People are integral parts of nature and, in many respects, are becoming dominant parts. This notion is implicit in the term “Anthropocene”. In no environment is the connection between people and nature more apparent than in coastal systems. Mutual causality between humans and nature plays out there on a daily basis, sometimes in very positive ways and other times in tragic ways. The enjoyment of coastal beauty and spiritual stimulation are among the positive attractions as are access to global seaways, fisheries and recreation. Death, disease and destruction wrought by severe storms and tsunamis are paramount among the downsides. But for a multiplicity of reasons, roughly half of the world’s 7 billion people live within 100 km (60 miles) of the shore. And the activities of those who live much farther inland, for example within the catchments of large rivers that run to the coast, impact the coastal environment and its residents in numerous ways. Human activities that directly impact coastal systems include urbanization, agriculture, nutrient runoff, engineering works, fisheries, oil and gas production, dredging and various forms of pollution. Natural processes that impact coastal residents include sea level rise, storms and storm surges, water-borne pathogens, tsunamis, and loss of ecosystem services. Important ecosystem services include pollination, decomposition, water purification, erosion and flood control, carbon storage, and climate regulation.

Coastal Complexity and Predictions of Change

Most people tend to think of coasts as material “things”. What you see when you look at a coast at any instant in time may be a beach composed of sand or a coastal wetland consisting of vegetation, mud and crabs and perhaps some methane or hydrogen sulfide gas. But in previous times it may have been very different and it probably will be different in the future. In reality, coasts are not “things” but processes; they are not static but are constantly becoming something new. This has always been the natural way with coasts. The ever-changing coastal process involves the interplay of solid material (e.g., sand and mud), chemistry (e.g., the pH of the Earth’s oceans), forces, energy fluxes and transfers (e.g., physical, chemical, biological, and solar), biological activity and ecological evolution, and, now, profound human interaction. We may reasonably expect coastal change to be accelerated in response to the climate changes that are now underway in the Anthropocene, a new geologic epoch in which human activities are causing profound and enduring modifications to the earth’s surface.

Impacts of Coastal Waters and Flooding on Human Health

Floods are among the most common natural hazards with complex and far-reaching impacts. Coastal floods are most often caused by storm surge (coastal), rivers that exceed their flood stage capacity (fluvial), and torrential rainfall (pluvial). Increasingly, compound flooding by all three causes is the most severe. The adverse consequences of flood events, especially coastal flooding, to human health. Drowning is the major cause of death, followed by heart attacks, hypothermia, blunt trauma caused by wind-borne objects and vehicle-related accidents. Snakebites, electrocution and wound infections are also causes of death. Less obvious health impacts involve diseases and toxins spread by water and water-nurtured vectors (e.g. mosquitos).

Global Change: More Than Climate

Coastal environments are changing throughout the world. Climate is only one of several drivers of change. Collectively, the suite of worldwide changes constitutes what is popularly referred to as “global change”. While climate is an essential and prominent member of that suite of changing environmental conditions, it is not the only thing that is changing or likely to change. In addition to increases in greenhouse gases, human contributions include several other anthropogenic sources of change that are less well-known.

Degradation of Coastal Ecosystems: Causes, Impacts and Mitigation Efforts

Coastal ecosystems are important for fisheries as fish nurseries and provide people with food security as well as livelihood opportunities. These areas, which include mangrove forests, coral reefs, and submerged aquatic vegetation beds, may be degraded by natural and anthropogenic events. Rich in species, coastal ecosystems are essential in storing and cycling nutrients, protecting shorelines, and filtering pollutants. The degradation of coastal ecosystems imperils species that rely on this habitat. Natural hazards such as tropical cyclones, climate fluctuations, and flooding cause ecosystem degradation. Coastal ecosystems have been exploited for development, recreation, and industry, worldwide. Over population, pollution, destruction of mangroves and coral reef for development, and overfishing degrade their health. Recent research has provided managers with a better understanding to plan and execute restoration projects. Marine protected areas have demonstrated the importance of monitoring restorations and recovery.

Causes and Impacts of Coastal Inundation

According to NOAA’s Office of Coastal Management, inundation events are the dominant causes of natural-hazard-related deaths in the U.S. and are also the most frequent and costly of the natural hazards affecting the nation. The effects of inundation in other nations such as Bangladesh, Indonesia, Thailand and India are often devastating. While the long-term rises in mean sea level as discussed in Part 1, Chap. 3 are instrumental in allowing inundation to reach farther inland and to ever higher elevations, it is the short-lived episodic, non-tidal, events that cause the most damage. Included among these inundation causes are tsunamis, storm surges, coastal flooding caused by onshore winds and wave-induced set up, river and inland flooding and extreme rainfall events. The deepest flooding occurs when two or more of these phenomena reinforce each other and coincide with perigean spring high tides (aka. “king tides”). For example, it is common for tropical cyclones to bring storm surges along with heavy rainfall and wave induced set up of mean water level. Structures such as levees that are designed to protect can also impede the return of floodwaters once overtopped. Navigation channels can also provide funneling pathways for surges.