Multiple Layers of Safety in the Netherlands and United States

Back on U.S. soil for nearly a year, I’ve linked up with another Dutch research institute to launch an initiative aimed at  comparing our two countries on one particular matter: implementing multiple layers of safety for improved flood risk management.


A comprehensive flood risk reduction plan would in theory reduce the frequency of floods, and it would also minimize the consequences once a flood occurs.

To do so requires implementing “Multiple Layers of Safety”  (the Lake Ponchartrain Basin Foundation has championed the similar “Multiple Lines of Defense”):

Dutch Concept of Multi-Layered Safety: (I) Prevention, (II) Protection, (III)

Dutch Concept of Multi-Layered Safety: (I) Prevention, (II) Protection, (III)

Layer 1:       Prevention

(addresses probability of flood through structural measures like dikes, levees, dams, storm surge barriers, bypasses, levee setbacks, etc).

Layer 2:      Protection

(addresses consequences of flood by insurance, limiting exposure through buyouts, zoning regulations, building codes and flood proofing, in-place protections, subway tunnel closures, etc)


Layer 3:      Preparedness

(addresses consequences of flood through evacuation, emergency response, and recovery).


Any flood risk reduction plan would require some level of investment in all three safety layers.

A flood risk management plan would require investment in managing both probability (prevention), and consequences  of flooding (protection, and preparation)

A flood risk management plan would require investment in managing both probability (prevention), and consequences of flooding (protection, and preparation)

Our research question: in a given flood-prone region in the United States and the Netherlands, what determines the relative level of investment in prevention, protection, and preparedness, and why?

  • From a purely risk-based perspective how would the relative size of each piece change with increasing/decreasing probabilities and consequences?
  •  What other factors at play would increase or decrease the relative size of each?
Flooded subway from Hurricane Sandy. source:

Flooded subway from Hurricane Sandy. source:

For example, how, where, and why will we rebuild the greater New York region? Will we build a storm surge barrier and go back to business as usual? Will we protect barrier islands? Elevate? Buy out? All of the above?

Dune nourishment for coastal protection. Source:

Dune nourishment for coastal protection. Source:

Why will the Netherlands indefinitely dredge the North Sea to nourish the coastal dunes no matter how costly it becomes?  Why don’t they have evacuations plans yet, and why do many Dutch engineers tend to scoff at communicating risk?

Why did Valmeyer relocate after the 1993 Mississippi Floods instead of build a levee or elevate houses?

Why after the risk-informed “Green Dot Map” leaked to the New Orleans public did many neighborhoods rebuild in place?

None of my questions above express a preference or an opinion. They’re just questions. Likely the answers are obvious to some you. The decisions behind the aforementioned examples may have been risk-based, though likely there were  also social, cultural, economic, or political factors at play, and those are what we want to elicit from the research effort.

Are there notable trends and preferences in the United States that are different from those in the Netherlands?  In the US, the National Flood Insurance Program has been identified as responsible for increasing risk.  In the Netherlands, there is no insurance program because none can afford to take on the risk (so the government does).

Subtle (or not so) differences in history, culture, political, and insurance systems have set the context for the two countries’ current state of flood risk.  The Netherlands may be arguably safer than the United States from a probability standpoint with 10,000-year protection on the Coast.  The United States may be arguably safer than the Netherlands from a consequences standpoint with experienced flood fighters and elevated houses.

Going forward, the goal of this study is to understand the rationale behind investing in  certain flood risk reduction measures and safety layers over others in attempt to identify barriers and opportunities to implementing multi-layered safety approaches in both countries.

There will likely be a survey and interviews later on to professionals in the field—ideally gathering opinions from people in all three sectors. Further, we will use case studies to illustrate themes highlighted in surveys and interviews.

We have some case studies selected already, but if you were involved in a particularly interesting (or boring) case, or want to participate in the study somehow, please comment on it here or send me a message with some of your thoughts.  For questions/comments on our proposed method, please send email.

Yesterday I was asked what commercial company is sponsoring this study and that answer is: none. This effort is funded through Unesco-IHE, and was developed by myself and my research partner after my year as a Fulbright fellow. We are very interested in applications of this topic in both countries.

Jessica (dot) ludy (at) gmail (dot) com.


About wateraway

Jessica Ludy is an independent researcher with Unesco-IHE, a Water Resources Planner with ARCADIS, and a Fulbright Scholar in Flood Risk Management at Delft Technical University, the Netherlands. She was formerly the Associate Director of Flood Management at American Rivers in Berkeley, California, where she worked to promote sustainable flood management strategies in regional, and state, and federal agencies. Jessica has also been a lecturer and researcher at UC Berkeley in the Department of Landscape Architecture and Environmental Planning. Jessica grew up on the Great Lakes in Michigan, earned a BSc at the University of Vermont in Environmental Science, and an MSc in Environmental Planning from the University of California, Berkeley. This website is not affiliated with the Fulbright commission, ARCADIS, TU-Delft, Unesco-IHE, or American Rivers.
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One Response to Multiple Layers of Safety in the Netherlands and United States

  1. Pingback: A Few Good Reads (4/8/13): The Aftermath of Flooding in Argentina » Hydraulically Inclined

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