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Floodplains by Design

Nuts and Bolts

Because of the many benefits that floodplains provide, people have been drawn to them since the beginning of human history. Today, floodplains represent some of the most heavily developed areas on Earth. But this development has come with a cost. Despite man’s best efforts at flood protection, history has repeatedly shown that floodplains will indeed flood, often with catastrophic consequences.

And the development of and changes to floodplains have greatly diminished their ability to provide benefits to people and nature. The goal of Floodplains by Design is to ensure floodplains are used and managed in ways that enable them to provide these valuable services, while maintaining or even improving flood protection. Accomplishing this goal means key natural processes and functions of the river and its floodplain must be maintained or, in some cases, restored.

Floodplains by Design also takes into account that all floodplains are different, and no one set of solutions will work in every case.

Think of those who implement the ideas behind Floodplains by Design as architects tasked with creating a plan that takes into consideration a wide range of factors. What is the extent of the floodplain? Where are the lowest lying areas? Where have communities and cities and other infrastructure been built? What flood protection measures – like dams and levees – exist?  During past floods, which areas “protected” and “unprotected” from floods were inundated? How is the river and floodplain used – for agriculture, barge traffic, commercial or recreational fishing, and other uses? Are there areas well suited for compatible uses – areas where crops tolerant to some flooding could be planted? Or are there areas where farmers find it difficult to make money due to regular flooding – areas that might be better suited for reforestation or other restoration efforts?

Another central concept of a Floodplains by Design approach is that those areas that flood most frequently – every one to five years – are the areas that are most valuable for nature, provide the most ecosystem services for people, and are most at risk of repetitive flood damages when developed. A Floodplains by Design approach calls for these areas to be managed differently than other areas of the floodplains.

Other key concepts of Floodplains by Design include:

  • Maximizing the use of natural infrastructure – working with, not against, natural processes as much as possible. A Floodplains by Design approach will draw on a number of tools and approaches that vary between rivers. Some of the key tactics here might include:
    • Setback levees, which are levees constructed or moved farther from the river into the floodplain, thereby allowing rising rivers more room. In many cases, those areas between rivers and levees or in connected floodplains are ideal for compatible uses – uses such as agriculture, green urban spaces, forestry lands, etc.
    • Connected floodplains, whether never “cut off” from the river by levees or other structures or “reconnected” by the removal or management of levees. The Conservancy’s Mollicy Farms in Louisiana is the largest floodplain reconnection project in the Mississippi River Basin.
  • Relying on a ‘diverse portfolio’ of flood-risk management tools, tailored to the specific requirements of the landscape. In addition to dams and levees as well as setback levees and connected floodplains, such tools can include floodways and flood bypasses, which are large-scale reconnections of floodplains for the storage and conveyance of water.
  • Planning and implementing practices and management decisions at the “whole-river” or watershed scale. Dams, levees, floodways, natural areas, topography, croplands, existing and planned developments, and river uses – like recreation, municipal water supply, irrigation, and navigation – are all interrelated and must be managed as such.
  • Planning a mosaic of land uses that are both resilient to flooding and consistent with vibrant rural communities; in other words, tailoring land use for the average frequency and duration of floods the area is subjected to.  
  • Maximizing the diverse benefits provided by floodplains and rivers.

The concept of Floodplains by Design can be difficult to grasp, which is why The Nature Conservancy has developed an animated video to help illustrate some of its basic concepts. Watch it now, but keep in mind all floodplains are different, and this video presents just one scenario and does so in a simplified and stylized manner. 

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