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How can communities be warned of impending danger from rising floodwaters in an area with little or no access to telephones or electricity?

For centuries, people along the Zambezi River relied on drumming to communicate information about river conditions, ranging from rapid flood warnings to less-urgent updates about gradually rising waters that helped people plan when to begin packing for the annual migration to higher ground.

This annual migration symbolizes a very different relationship to floods than exists today along the lower Zambezi, and indeed, in most parts of the world. Now floods are assumed to be controlled and traditional warning systems have faded. It is true that the annual floods that were so beneficial for both rural communities and ecosystems are largely gone. But what remains are the occasional sudden and deadly large floods that devastate communities without warning.

Restoring traditional connections between communities and flooding can reinvigorate ecosystems, enhance livelihoods and save lives.  Making the connection between these objectives is a great challenge and opportunity for conservation groups like The Nature Conservancy as we work on the Zambezi River.

For millennia, the Zambezi collected the summer rains from the highlands, swelling and then easing out of its banks into vast surrounding floodplains. These floodplains were the engines of productivity for both aquatic and terrestrial ecosystems as well as rural communities. People depended on the floodplains’ abundant wildlife and fisheries, lush grasses for livestock, and groundwater–replenished after each flood–which supported crops as the waters receded.  Life centered around the river and its annual flood, as beautifully celebrated in this poem from the Barotse people who lived along the Zambezi in western Zambia:

It is flood time in Bulozi.

The floodplain is clothed in the water garment.

Everywhere there is water!

There is brightness!

There are sparkles!

Waves marry with the sun’s glory

Birds fly over the floods slowly,

They are drunken with cool air.

They watch a scene which comes but once a year

Floods are beautiful.

This poem goes on to describe a festival—the Kuomboka (literally, “moving out of the water”)—which is still practiced today along a free-flowing section of the Zambezi.  The festival is preceded by drumming that alerts communities that the river is rising and it will soon be time to move to higher ground.

In the Zambezi delta (where the river enters the Indian Ocean in Mozambique), people also previously used the floodplain only seasonally—for fishing, hunting, grazing and agriculture—and built their permanent buildings on higher ground. Drumming may have been an important source of information about river conditions hundreds of miles away, helping communities plan the timing of their movements, as well as a source of immediate warning of flash flooding from tropical cyclones. (Anthropologists call this practice “drum telegraphy” and it has been used by cultures throughout the world).

Today the Zambezi Delta is a different place. A massive hydroelectric dam, Cahora Bossa, dramatically changed the river’s flows and stopped floods in nearly all years.

After the dam, fish harvests in the river and prawn harvests in the estuary dropped precipitously and, as the floodplains dried up, so did the availability of good forage for livestock and groundwater for crops. Wildlife also suffered and numbers declined steeply.

Perversely, the reduced flooding may have actually increased the flood danger to people. Historically, the annual floods served as a frequent reminder of how high the river could reach; communities thus sited their homes and economic activities to avoid dangerous floods and maximize the benefits from productive floods. Once the dam stopped the frequent floods, permanent communities were established in the floodplains. The drum-based flood warning system no doubt faded away. The river is now more-or-less tamed.

Except when it isn’t.

While in the past the river rose relatively slowly as the flood gathered strength from far-flung tributaries, now the dam-managed river occasionally—and suddenly—breaks out from its confinement.  The results can be catastrophic.

In 2007, heavy rains lead to a surge of inflow to Cahora Bassa’s reservoir that then “spilled” over the dam with little warning, killing people and displacing hundreds of thousands in the downstream Delta.

Not only have the communities lost their economic and cultural connections to the productive annual flood, they now associate flooding with catastrophe. This perception complicates our efforts—as part of a coalition that includes WWF, the International Crane Foundation and agencies and universities from Zambia, Zimbabwe and Mozambique—to restore the ecological health of the Zambezi River. 

Restoring a managed flood release from Cahora Bassa into the Delta has the potential to significantly improve conditions for both wildlife and people, particularly the rural poor who depend on the Delta’s fish, prawns, grasslands, and groundwater. However, managed flood releases must overcome the newly developed biases against floods shaped by tragic events in recent decades.

One way to do that may be to clearly demonstrate that, in addition to improving the health of the delta, the release of managed, intentional floods can actually make people safer from uncontrolled floods.

Currently, the International Federation of Red Cross and Red Crescent Societies (IFRC) is working on a project to reduce flood vulnerability in the Zambezi basin, including development of early warning systems. The flood-warning system will strive to deliver accurate and timely information to communities using everything from the most current technology to traditional means such as colored flags and drumming. Other ideas include self-powered radios and taking advantage of the rapid proliferation of cell phone ownership in Africa to institute a “reverse 911” system, wherein a network of sophisticated monitoring instruments can quickly (perhaps even automatically) send out warnings as text messages on cell phones.

How does this relate to the Conservancy’s goals of restoring managed floods to the delta? While the “restoration” floods will be no where near as high, rapid, or dangerous as the rare uncontrolled floods, they will still require effective communication with remote and hard-to-reach rural communities. Thus, these managed floods can provide an excellent opportunity to prepare and test flood warning systems with actual, albeit much less dangerous, floods. Government agencies, relief organizations and communities can practice communicating in advance, and in real time, about floods.

Linking managed, intentional floods with the development and testing of flood-warning systems is just one piece of a larger concept — floodplain restoration and reconnection can make people safer from all floods by promoting land uses that reduce the potential for catastrophic losses while allowing floodplains to provide to society their characteristic multiple benefits.

-- Text by Jeff Opperman, Cool Green Science Blog
From drumbeats to texts & tweets: Different ways to say 'The river is rising'
Managed floods can provide the opportunity to prepare and test flood warning systems with actual, albeit much less dangerous, floods.