A Fresh View of Floodplain Ecology and Management

by Jeff Opperman and Peter Moyle, co-authors of Floodplains: Processes and Management for Ecosystem Services

Last week, we saw tragic images of floods across the world, from Houston to Niger to south Asia, with more than 1,300 deaths from floods in India, Nepal and Bangladesh.

Floods are among the most costly natural disasters worldwide and the loss of life and property, from Houston to Mumbai, gave a very human face to the impersonal statistics: in recent years, global damages have ranged between $30 and 60 billion and more than 100 million people have been displaced by flooding.

These events are also warnings about a likely future: in a warming world, many regions will experience more frequent and intense flooding.

It is hard to imagine a flood-management system that could have effectively contained the historic amount of rain that fell on southeast Texas—several feet in just a few days. However, even if all floods can’t be contained, governments must still invest in measures to improve safety for people and reduce damages. The key is to move beyond a primary focus on the structural measures—dams and levees—that strive to contain floods, and toward a “diversified portfolio” approach. Nonstructural measures—such as zoning, building codes and insurance—are key to keeping people out of harm’s way. Another critical strategy is to integrate green infrastructure—natural features such as wetlands and floodplains—into flood-management systems.

In river basins around the world, from the Mississippi to the Sacramento to the Rhine, managers have moved away from a strict reliance on engineered levees, which confine rivers and attempt to contain floods. Instead, they have moved towards reconnecting rivers to parts of their historic floodplains. On these reconnected floodplains, floodwaters can spread out and reduce risks to communities and farmland in other areas.

We have documented this trend, and reasons why green infrastructure can be so effective, in our book, Floodplains: Processes and Management for Ecosystem Services.

The book is based on our many years of studying floodplains in California, a leader in using floodplains for flood management. But we also explore other regions, especially Europe, Australia, and Asia, for new insights.

Our focus is reconciliation ecology, the science of integrating functioning ecosystems into landscapes dominated by people. This framework is key to understanding the full potential of green infrastructure: by reducing flood risk, wetlands and floodplains function as infrastructure. But they are also “green”—they are ecosystems that are influenced by complex and intertwined biophysical processes. The first part of our book reviews these processes—encompassing hydrology, geomorphology, biogeochemistry, and ecology—and how they respond to management interventions.

A hallmark of green infrastructure is that these ecosystem processes can provide multiple benefits beyond flood-risk reduction. For floodplains, these benefits include habitat for fish and wildlife, groundwater recharge, carbon sequestration, and open space and recreation. Thus, realizing the full potential of green infrastructure will come from an integrated approach, one in which engineers, scientists and planners collaborate on management to provide multiple benefits. The second part of the book includes a number of case studies of these new management approaches.

To be clear, we are not suggesting that floodplains and wetlands are the answer to reducing current and future flood risk. Rather, we think that a flood-management system that relies on green infrastructure in addition to engineered infrastructure and sound nonstructural policies, will increase safety for people and provide a broad range of other benefits.

The book’s closing paragraph articulates this optimism that integrated management can improve safety for people while promoting a range or natural services:

“Our time spent on rivers and floodplains has certainly shown us that much has changed and been lost over time. But we have seen more than just glimmers of hope in reconciled floodplains that are diverse and productive. We take heart from the huge flocks of migratory white geese and black ibis that congregate annually on California floodplains and from knowing that, beneath the floodwaters, juvenile salmon are swimming, feeding, and growing among cottonwoods and rice stalks, before heading out to sea. We can envision greatly expanded floodplains that are centerpieces of many regions, protecting people but also featuring wildlands, wildlife, and floodplain-friendly agriculture. Connectivity among floodplains, people and wild creatures is within reach, as is a future in which people work with natural processes rather than continually fighting them.”

Jeffrey J. Opperman is the global lead freshwater scientist for WWF and a research associate at the University of California, Davis.

Peter B. Moyle is Distinguished Professor Emeritus in the Department of Wildlife, Fish, and Conservation Biology and Associate Director of the Center for Watershed Sciences at the University of California, Davis.