Here come the floods

The first flood of the season arrived early in Natchez, Mississippi.

Meteorologists at the Lower Mississippi River Forecast Center of the National Weather Service had been tracking late January rainfall (“high-water events”) upstream in the Mississippi River Basin.

On Jan 21, the Tennessee River Valley got 1-2 inches of rain, on Jan. 22 the Ohio River Valley received 1.5 inches, on Jan. 24 1.5 inches fell over the Missouri River Valley and on Jan. 25 the Tennessee River Valley received another 1.5-3 inches of rain.

Under “normal” conditions, the Mississippi doesn’t rise significantly until March, as snow melt and other precipitation starts flowing down the river. Even prior to this early precipitation, autumn had dumped substantial rainfall on the Midwest (“the wettest October ever in St. Louis”). As a result, water tables are already high. Spring rain on top of a saturated ground equals more flooding.

Communities along rivers in the Midwest are bracing for would could be a whopper of a spring flood season, with the National Weather Service warning of a “high probability” of significant flooding along parts of the Mississippi and Missouri rivers and their tributaries.

Big Watershed

The Mississippi River Basin is remarkably vast, drawing water from 31 states and two Canadian provinces and covering 40% of the continental United States. Water takes approximately three months to flow from the headwaters at Lake Itasca, Minnesota, to the Gulf of Mexico. Imagine the rain and snow melt shedding off this broad landscape, collecting in the capillaries of streams, merging into rivers, and amassing into the slow wave that rolls down the Mississippi. On the Lower Mississippi, forecasters can see a flood building a long way upstream.

On February 8, the Mississippi reached flood stage at Natchez. While the crest of the flood has already passed New Orleans, flood stage waters continue in some areas between Natchez and Baton Rouge. As the river remained above the 48-foot natural riverbanks this past weekend, crews in Natchez keep a close eye on “sand boils” that form as water displaces soil under the city’s levees. Sandbagging around these boils is part of the seasonal fight against floods. When the river subsides, the crews will wait for the next rise later this spring.

A report from the U.S. Global Change Research Program predicted for the Midwest:

“an increase in precipitation in winter and spring, more heavy downpours, and greater evaporation in summer, leading to more periods of both floods and water deficits.” More “droughts, floods and other extreme events,” in other words.

The flood of media

While the weather is a topic of daily chatter pretty much everywhere, I suppose most people in the U.S. pay little attention to river levels these days. “How’s the hydrological cycle?” rarely comes up in polite conversation. Rivers (and the seas) aren’t as central to most people’s livelihoods or for commerce and transportation as they once were — even though 500 million tons of commercial traffic continues to move on the Mississippi each year.

As spring nears and so does the snow melt, media coverage of Midwestern floods is beginning to appear.

Floods tend to be treated by the media as isolated — and dramatic — news stories. Throughout the year, some part of the world is likely to be passing through its rainy season. So flood stories are not hard to find.

Recent headlines from around the world:
Lusaka: Eight people die in heavy Zambian floods due to poor drainage
Afghanistan: Afghan floods, avalanches kill 20
São Paulo: Living with the floods
Cumbria, Ireland: The extreme floods in Cumbria
Madeira, Portugal: Madeira floods kill 42, divers hunt for missing

Treehugger recently posted this slide show on the destructive power of floods. The media coverage of the “Snowpocalypse” on the East Coast may transform into news of floods. And, alas, flood stories will become part of the saga in post-quake Haiti, especially when hurricane season arrives.

“Natural” disasters

Floods undoubtedly unleash tremendous pain and suffering around the world, wreaking havoc on the assumed stability of human social and economic affairs. What makes a flood a “natural disaster” — and a headline — is the presence of humans. The combination of human population growth, the expansion of settlements along rivers and coastlines, and increasing threats from climate destabilization will certainly mean more floods:

Droughts and floods account for more than half of the world’s total deaths from disasters, according to the United Nations. But unlike many other catastrophes, most water crises are man-made. Nature may bring the occasional monsoon downpour or dry spell, but environmentalists agree that global warming, dams, deforestation and slash-and-burn farming exponentially exacerbate these seasonal weather patterns.

Sea-level rise, storm surge, and extreme weather events will all contribute to coastal and riverine flooding. In many parts of the world, sewage, toxic runoff, and water-borne disease, like cholera, extend the impact of floods. Inevitably, the most vulnerable communities bear the burden of these disasters. In the U.S., of course, the disproportionate burden of Hurricane Katrina on the poorest residents of New Orleans remains the most visible example.

A flood, in a way, poses a variation on the old question, “If a tree falls in the woods and no one is there to hear it, does it make a sound?” Is it a media story? Flood and flooding are often used interchangeably. Perhaps there’s a distinction between a “flood” and “flooding.” A “flood” represents a condition or an event. “Flooding” is both a local phenomenon and a process, part of the temporal ebb and flow of ecosystems, the timeless hydrological cycles under which landscapes and other species have evolved.

Channeling the river

Since the late 1800s, the Mississippi River Commission has focused on improving navigation and flood control on the lower Mississippi. In 1928, the MRC launched the Mississippi River and Tributaries project, one of the world’s most extensive engineering projects, led by the Army Corps of Engineers.

In order to maintain “order,” much of the Upper and Lower Mississippi River has been dramatically channeled with levees and reservoirs and locks, in the process destroying wetlands and altering the flow of water and sediment. The Mississippi River Delta is in terrible shape. In the state of Missouri, the river now has less than one-fifth of the original wetlands. According to Ana Barros, a civil and environmental engineer at Penn State,

A channel has no capacity to adapt to variable conditions. Tamed, constricted, “It can’t evolve to prepare itself for the next event. This river has nowhere to go.”

For Barros, part of understanding the river is learning to respect it: recognizing that ultimately it will not be controlled. “We must learn to work with the river instead of against it.” This means recognizing the river as a complex, self-regulating system, and seeking to restore as much of its integrity as possible. At the same time, she says, “We have to anticipate the worst, and design systems that work well in failure.”

River restoration is a critical and growing field. Reconnecting the river and floodplains will help to reduce flooding. Even the Corps has begun to integrate conservation biology principles. But the field also needs more coordination and will have to evolve as our understanding of climate change and river ecosystems deepens.

Learning to work with the natural systems will also inevitably force significant tradeoffs. Along the Mississippi, agriculture and urban centers have expanded in conjunction with the channelization of the river. Reintegration of natural buffer areas will place constraints on the location of development along the river. Commercial traffic on inland waterways will also have to adapt. But this is a long-term process of necessary rethinking and restoration.

Ultimately, this restoration involves shifting the focus from “floods” to “flooding.” As Ana Barros suggests, we will have to learn to respect the river. We can also reacquaint ourselves with and embrace the pattern of the river:

Rivers pulse in reflection of the seasons. When there is snowmelt and during rainy seasons, the total volume of water in the river increases.  As water in the river channel rises, islands and riverbanks that are usually exposed are submerged. Increased levels of water scour the land it flows over and increases the amount of sediment carried with the current.  The process is reversed in the dry season. Land that was submerged is exposed, less water and slower current allow particles to settle out of the water and be deposited on the riverbed itself. Year after year this cycle is repeated.

Thanks to @River_Restore, @NEMWIUpperMiss, @DDimick, @troutheadwaters

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Tagged as: Army Corps of Engineers, climate change, flood, flooding, Mississippi River, restoration, watershed