Climate change and urbanization pose significant threats for flooding and water quality in urban areas.
Climate change
Global climate is projected to continue to change over this century and beyond. The magnitude of climate change beyond the next few decades depends primarily on the amount of heat-trapping gases emitted globally, and how sensitive the Earth’s climate is to those emissions.
Changes in Precipitation Patterns
Average U.S. precipitation has increased since 1900, but some areas have had increases greater than the national average, and some areas have had decreases. More winter and spring precipitation is projected for the northern United States, and less for the Southwest, over this century.
Projections of future climate over the U.S. suggest that the recent trend towards increased heavy precipitation events will continue. This trend is projected to occur even in regions where total precipitation is expected to decrease, such as the Southwest.
Hurricanes Will Become Stronger and More Intense
The intensity, frequency and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.
Sea Level Will Rise 1-4 feet by 2100
Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 4 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.
In the next several decades, storm surges and high tides could combine with sea level rise and land subsidence to further increase flooding in many regions. Sea level rise will continue past 2100 because the oceans take a very long time to respond to warmer conditions at the Earth’s surface. Ocean waters will therefore continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than those of the current century.
Regional Effects
Climate Change in Coastal Communities
What are the potential impacts of climate change to estuaries and coastal areas?
Estuarine systems are particularly vulnerable to many of the projected effects of climate change, such as:
- Sea level rise
- Increased temperatures
- Changes in precipitation and storm intensity
- Ocean acidification
Examples of specific impacts that may occur in estuaries and other coastal areas include:
- salt-water intrusion into aquifers as the sea rises,
- flooding of coastal wetlands and marshes,
- changes to water availability and quality,
- changes in habitat and species distributions,
- lower oxygen levels in wetlands,
- ocean acidification (due to higher concentrations of carbon dioxide in the atmosphere), and
- a range of impacts from more severe coastal storms.
These impacts may occur in tandem with other existing stressors, such as coastal population growth, presenting new and different challenges to National Estuary Programs and coastal communities.
What can be done to make estuaries climate ready?
Coastal resource managers can reduce risks and improve resiliency by:
proactively identifying areas that are particularly vulnerable, monitoring for changes, and developing and implementing adaptation plans. These adaptation plans may contain a wide range of adaptation actions that are designed to reduce impacts or exploit beneficial opportunities resulting from climate change.
Adaptation plans are linked to management goals, such as maintaining water quality of marshes and wetlands, protecting coastal development, preserving habitat, or controlling invasive species.
For example, if the management goal is to maintain wetlands, adaptation strategies might include:
prohibiting the construction of bulkheads, establishing rolling easements, or incorporating wetland protection into the planning of new infrastructure. If the goal is to maintain sediment transport, managers could:
trap or add sand through beach nourishment, remove barriers to sediment deposition on wetlands (e.g., levees), or trap sand through the construction of groins.
Why should coastal resource managers focus on adaptation?
Reasons why coastal managers should focus their efforts on adapting to climate change include:
Vulnerability: Coastal zones are highly vulnerable to climate change. Climate-driven impacts will be further exacerbated by other human-induced pressures (IPCC 2007). Timing: Coasts are already experiencing climate change impacts. The Earth is committed to additional impacts due to past and current greenhouse gas emissions. Adaptation planning is necessary to address these already unavoidable impacts. Opportunity: Adaptation can help reduce the long-term costs of climate change impacts (IPCC 2007). See Adaptation Planning for the National Estuary Program.
Rapid Urbanization
The natural water cycle is being changed by urbanization.
Population Growth
Land Use Change
Aging Infrastructure
Wastewater and stormwater collection and conveyance systems are undergoing aging and deterioration, leaving cities vulnerable to flooding and water quality degradation. To avoid such problems, utilities began implementing some sort of urban drainage infrastructure asset management systems.
©Biao Huang @Ningbo University