Connecting Delta Cities


FEMA Releases Updated Flood Maps for New York City

On December 5, the Federal Emergency Management Agency (FEMA) identified areas of the City at risk of flooding in new Preliminary Flood Insurance Rate Maps (FIRMs) and also issued a narrative report of the city’s flood hazard in a Preliminary Flood Insurance Study (FIS).  The issuance of the Preliminary FIRMs and FIS marks the first step in the regulatory review process, which includes a public comment period followed by a statutory 90-day appeals period before the City adopts the maps as the new Effective FIRMs, expected in 2015.  In the meantime, Local Law 96, which goes into effect January 6, 2014, requires all new and substantially improved structures in the updated floodplain to be built to the standards reflected in the Preliminary FIRMs.  This helps preserve the communities along New York City’s 520 miles of coastline by ensuring that homes and businesses are built to withstand flooding and by reducing potential future flood insurance costs.

Members of the public can submit comments here.
Maps can be viewed on FEMA Region 2’s website.

A stronger, more resilient New York.

On June 11, Mayor Michael Bloomberg announced “A Stronger, More Resilient New York”, a comprehensive plan that contains actionable recommendations both for rebuilding the communities impacted by Sandy and increasing the resilience of infrastructure and buildings citywide.

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Press Release: C40 Cities Announces New Clinton Global Initiative Commitment to Help Cities Prepare for Severe Weather and Natural Disasters

MAY 6, 2013 (New York, NY) – The C40 Cities Climate Leadership Group (C40) today announced a new Clinton Global Initiative (CGI) Commitment to Action that will help cities better prepare for natural disasters and severe weather incidents. The new C40 Risk Assessment Framework will create a common approach for cities to assess climate risk and provide a process to help cities prioritize risk before investing in climate actions.

“In the wake of Hurricane Sandy and the recent floods in Jakarta and Sao Paulo, it is clear we need to empower cities to take the necessary actions to protect their citizens, infrastructure and economies from the devastating impacts of natural disasters,” said C40 Chair, New York City Mayor Michael R. Bloomberg. “While a growing number of cities have efforts underway to measure climate risk, there is a high degree of uncertainty and variability in their methodologies and approaches. The C40 Risk Assessment Framework, by creating a common approach to this challenge, will become the global standard by which all cities measure and manage climate risk."

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Tokyo: G-cans project

Tokyo G-cans project: widely known as Tokyo underground flood tunnels is the networks of tunnels 6.4 kilometers (four miles) long built deep under the ground in the Tokyo suburbs. All this infrastructure is dedicated to prevent flooding when Tokyo metropolitan area rivers are overfilling during the rain seasons or in case of typhoons.


Surge Generation Mechanisms in the Lower Mississippi River and Discharge Dependency

The Lower Mississippi River protrudes into the Gulf of Mexico, and manmade levees line only the west bank for 55 km of the Lower Plaquemines section. Historically, sustained easterly winds from hurricanes have directed surge across Breton Sound, into the Mississippi River and against its west bank levee, allowing for surge to build and then propagate efficiently upriver and thus increase water levels past New Orleans.

This case study applies a new and extensively validated basin- to channel-scale, high-resolution, unstructured-mesh ADvanced CIRCulation model to simulate a suite of historical and hypothetical storms under low to high river discharges. The results show that during hurricanes, (1) total water levels in the lower river south of Pointe à La Hache are only weakly dependent on river flow, and easterly wind-driven storm surge is generated on top of existing ambient strongly flow-dependent river stages, so the surge that propagates upriver reduces with increasing river flow; (2) natural levees and adjacent wetlands on the east and west banks in the Lower Plaquemines capture storm surge in the river, although not as effectively as the manmade levees on the west bank; and (3) the lowering of manmade levees along this Lower Plaquemines river section to their natural state, to allow storm surge to partially pass across the Mississippi River, will decrease storm surge upriver by 1 to 2 m between Pointe à La Hache and New Orleans, independent of river flow.

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Note: Downloading this article requires logging in and possibly payment. The article was first published in Journal of Waterway, Port, Coastal, and Ocean Engineering, volume 139, issue 4 (July 2013).

Main publications

Magazine "Resilient Cities and Climate Adaptation Strategies" CDC book volume 3 Available now. Download free of charge.

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