New Climate Measure Restricts Floodplain Development

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President Barack Obama has just taken unprecedented actions to help coastal communities resist severe impacts of climate change. Anywhere that taxpayer dollars are used to build or protect floodplain development of buildings, roads, and other infrastructure, agencies must now consider current and future flooding risks to alterations and new housing, transportation, energy, water supply, and more. In other words, we must not continue to build where our money may be wasted when new construction washes out.

Miami floodplain at risk from sea level rise with climate change. (Foreground: PlanetSolar, the world's largest solar-powered boat and first ever solar electric vehicle to circumnavigate the globe. (Photo: wikipedia/Florence8787, public domain.)

Initially mandated into law in 1978 and governing development activity in US floodplains for almost 40 years thereafter, Executive Order 11988 (Floodplain Management) states that “losses caused by flooding affect the environment, our economic prosperity, and public health and safety, each of which affects our national security.” The President amended the order on Friday, January 30, 2015, to improve the Nation’s preparedness for and resilience against flooding related to shifts in world climate.

Climate change involves water levels rising worldwide. As the climate continues to shift, rising sea levels, more intense storms, and heavier rainfall are increasing flood impacts. In the Marshall Islands, where land level only exceeds the sea by six feet, rising waters have been washing up dead soldiers from World War II. Other island nations have evacuated or are taking steps to leave their ancestral homes. In fact, according to a study published in the major world journal Nature two weeks ago, sea levels have risen in the past two decades faster than previously thought. All corners of the world are seeing flooding, even on 100% sunny days.

Limit of moderate wave action (

Over the past three decades, the United States has suffered more than $260 billion in flood-related damages. These include both disasters like Superstorm Sandy ($67 billion, and counting) and record flooding along inland waterways and low-lying areas. More than 50% of Americans live in coastal counties, and over $1 trillion of property in the U.S. is prone to inundation from a sea level rise of only two feet–an elevation that some experts say could be reached as early as 2050.

The US government is required by law to take action to uphold the resilience of our shoreline communities and federally owned assets against flood risk. In accordance with the government’s Climate Action Plan (announced on June 25, 2013), the US National Security Council staff has led an interagency effort, with input from state governors, mayors, and other stakeholders, to reexamine the guidelines from the 1970s and update them. Says the White House Council on Environmental Quality in a fact sheet:

“By requiring that Federally funded buildings, roads and other infrastructure are constructed to better withstand the impacts of flooding, the President’s action will support the thousands of communities that have strengthened their local floodplain management codes and standards, and will help ensure Federal projects last as long as intended.”

We now have an up-to-date and proactive national management standard for flood risk reduction affecting federally funded projects. The chart here presents its eight essential steps.

Floodplain management decisionmaking process for EO 11988 (

Agencies involved in floodplain management ( address current and future flood risks and protect taxpayer investments, the amended flood risk standard requires federal agencies to expand managed floodplains from the current base flood level to a higher vertical elevation and its corresponding horizontal floodplain. This change expands the area of agency responsibility. The President’s new order requires departments and agencies to avoid both long- and short-term adverse impacts associated with floodplain occupancy and modification. It also requires them to avoid direct or indirect support of floodplain development wherever there is a practicable alternative.

The new regs are particularly important because they will protect high-ticket public investments like reservoirs and waste treatment facilities, which have long-term operation, maintenance, and repair programs. In essence, the order declares that responsible jurisdictions may select one of the following approaches to determine the area of a floodplain:

  • Best-available, actionable hydrologic and hydraulic methods that integrate current and future flooding changes based on climate science. (These will also specify whether the action is considered critical, i.e., “any activity for which even a slight chance of flooding would be too great”—a case for which the impacts of flooding on human safety, health, and welfare cannot be minimized without stepping up resilience mandates critical action.);
  • Freeboard value, reached by adding 2 feet to the base flood elevation (standard projects, considered noncritical actions) for the 0.2% annual chance flood (the 500-year flood);
  • Area subject to flooding by the 3-foot standard (such as critical buildings like hospitals and evacuation centers); or
  • Using any other method identified in an update to the FFRMS.

The head of an agency may except an agency action in the interest of national security, where application to a Federal facility is inappropriate, or for an agency action that is mission-critical for a national security interest or an emergency action. In any of these cases, the agency head will rely on the base flood area.

Coastal and Riverine Hazard Area Maps (

Also, the new guidelines incorporate the use of natural features and nature-based approaches in limiting coastal losses. (The Corps of Engineers suggested these low-cost shore protection measures over 30 years ago.) The Mitigation Framework Leadership Group, in consultation with the Federal Interagency Floodplain Management Task Force, must reassess the standard annually, after seeking stakeholder input, and provide recommendations to the Water Resources Council (established by the Water Resources Planning Act [79 Stat. 244], July 22, 1965) to update the standard if warranted. The Water Resources Council must issue an update to the standard at least every 5 years.

Rachel Cleetus, Lead Climate Economist at the Union of Concerned Scientists, applauds the new standard:

Nuisance flooding timetable (“This should be one of the least controversial executive orders the president has ever released. Why would the federal government build or repair buildings in ways that continue to put communities at risk? And why would we waste taxpayer dollars rebuilding in ways that are likely to result in repeated future flooding damages? This executive order is simply common sense.”

The UCS put out a very informative guide to future East and Gulf Coast flooding last October called “Encroaching Tides.” The tidal flooding and nuisance flooding charts shown here (below and at right) come from that publication.

Along with the President’s executive order, the Federal Emergency Management Agency has just published for public comment draft amended Floodplain Management Guidelines for Implementing Executive Order 11988. You’ll find an informative fact sheet about taking action to protect communities and reduce the cost of future flood disasters here.

Tidal flooding today, 2030, 2045 (

Also this week, the Army Corps of Engineers released a comprehensive study of current flood risks to coastal areas affected by Hurricane Sandy. It provides help for communities addressing increasing flood risks there.


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