Coastal Flood Control

cainc-coastal-floodingThe need to support environmental services, including coastal restoration, has accelerated due to the increased stress resulting from both human and natural impacts. The main focus is on water resources and coastal zones, particularly those in climate-sensitive or urban coastal areas which are becoming more vulnerable to flooding.

Changes in climate will threaten the efficacy, adequacy, and durability of flood control structures and their continued services. Since flood control structures provide defense against frequent, small floods in rivers and estuaries, rising sea levels, and storm surges, climate change impacts on these structures may significantly affect the communities relying on their protection. Such impacts have implications for urban stability, economic growth and trade, and food and water availability. These structures and their services can be protected with adaptation strategies that include fortifying existing structures and updating design standards to accommodate future climate changes.

Flood control structures are integral to development priorities. They are designed to protect coastal and river-bank areas, including urban and agricultural communities, homes, and other economically valuable areas, and the people located within them. These structures are used to divert flows of water, by re-directing rivers, slowing natural changes in embankments and coastlines, or preventing inundation of vulnerable coastlines or floodplains. Dikes, spurs, levees, and seawalls often act as the first line of defense against overflowing rivers, floods, storm surges, and, in the longer term, rising seas. By keeping water out, flood control structures lessen harm to physical infrastructure and help to ensure continuation of communities’ economic and social activity.

But flood control structures do not completely eliminate risk. Flooding may occur if the design water levels are exceeded. If poorly designed, constructed, operated or maintained, these structures can increase risk by providing a false sense of security and encouraging settlements or economic activity in hazard-prone areas.

Nevertheless, many development programs rely on these structures to maintain program objectives, including continued food and water supplies, economic activity, and protection from storms and floods. For example, urban initiatives (e.g., urban transport projects) in coastal cities like Dhaka, Bangladesh necessarily rely on effective flood control structures, such as pump stations and dikes, to maintain program effectiveness in the short-term. By supporting the climate-resilient design, construction, and maintenance of flood control structures, USAID and other development practitioners can help ensure the lasting effects of development projects and programs in vulnerable areas.

To reduce climate change impacts on flood control structures and the resulting damage and destruction to coastal and low-lying communities, development practitioners must adapt flood control structures to future climate stressors. Adapting flood control structures will protect investments in a variety of sectors, including transportation, energy, and urban programs.

The resilience of flood control structures can be increased in many ways. For example, flood control structures should be built to higher levels and with more resilient materials and designed to withstand repeated and more extreme floods. Similarly, in designing flood control structures, USAID and other development organizations should consider, where feasible, constructing back-up structures to provide services in case of failure. In addition, design standards should incorporate sea level rise projections, as well as the hydrology and physiography of the watershed to minimize or avoid unintended adverse impacts.

To understand the implications for flood control structures, decision makers should identify plausible future climate scenarios to understand how relevant factors, such as sea levels and extreme event intensity, are projected to change. Using this information, decision makers can identify needed changes to the design, construction, and maintenance of structures. Development practitioners must understand the vulnerabilities of different structures, based on location, design, and construction in addition to hydrologic, environmental, and ecosystem impacts. Adaptation actions should be integrated into the overall risk management strategy for flood control structures.

Headquartered in Westhampton Beach, N.Y., Chesterfield Associates Inc. provides an array of services in marine contracting throughout the Mid-Atlantic States, counties and municipalities. Although Chesterfield Associates is able to meet the needs of nearly any particular job, the reality is that there’s no economically feasible way to protect all 580-plus miles of New York City coastline from truly catastrophic sea level rise and super-storms, let alone other American cities, like Miami or New Orleans, that are even more vulnerable to flooding. That doesn’t mean we shouldn’t learn from what foreign cities have done and take major steps to defend our most valuable coastal real estate. But sea walls and barriers will only be one part of a multi-faceted response to a warmer, more crowded world. There’s no perfect defense from nature, especially a nature that’s been turbo-charged by human activity.

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