New Walls Aim to Hold Back Rising Seas off Tanzania

Coastal erosion and flooding threaten Dar es Salaam, one of Africa’s fastest-growing cities

New Walls Aim to Hold Back Rising Seas off Tanzania

Tanzania’s vice president, wearing sunglasses and a bright yellow hijab, leaned over the waist-high concrete sea wall along Barack Obama Drive and gazed upon an expanse of Indian Ocean.

It was June 5, World Environment Day, and Samia Suluhu Hassan had traveled to the busy roadside in Dar es Salaam, Tanzania’s economic capital, to mark the completion of one of the country’s most visible climate adaptation projects.

More than 11 years had passed since Tanzania adopted its National Adaptation Program of Action, which identified “the construction of artificial structures, e.g., sea walls” as a priority to offset projected sea-level rise of between 1.5 and 3 feet over the coming century. (Subsequent studies have estimated sea-level rise in Tanzania will be between 0.5 and 1.4 feet by 2050.)

So Suluhu Hassan had reason to celebrate as she peered over the wall, which provides up to 20 feet of vertical protection from the surf below. “To take steps to combat climate change is a must for us as a country,” she said. “So now building this wall is our way to defend and reduce the effects of climate change.”

More than 5 million residents of Dar es Salaam, along with millions more Tanzanians who live along the country’s coast of almost 900 miles, are counting on the government to make good on its assurances.

Without action, experts say, the Tanzanian coastline could become inundated with seawater by the end of the 21st century. Such an outcome would be devastating for East Africa, one of the world’s emerging commercial hubs, and it could permanently scar Dar es Salaam, the largest and fastest-growing city in Africa’s coastal zone.

“A warmer ocean and rising sea levels threaten the way women, men and children live along the world’s coasts,” said Grete Faremo, executive director of the U.N. Office of Project Services, which helped implement the construction of seven new sea walls along Tanzania’s coast.

“There is no question that we must work together to help our most vulnerable populations cope with an uncertain future,” he added.

Together, the sea wall projects defend about 1.5 miles of heavily eroded coastline at a cost of more than $8 million, according to the United Nations. Their construction is part of a broader effort to address sea-level rise, using walls and greener solutions like mangrove restoration.

Funding for the projects came from the U.S.-based Adaptation Fund ($5 million for the Dar es Salaam projects) and the Global Environment Facility’s Least Developed Countries Fund ($3.34 million for projects outside Dar).

The U.S. Agency for International Development, in its latest climate risk profile for Tanzania, noted that sea-level rise is expected to cause about $200 million per year in lost land and infrastructure damage countrywide. And in Dar alone, $5.3 billion in public and private assets are at risk from flooding and sea-level rise, USAID determined.

Yet according to sea-level-rise expert Robert Nicholls of the University of Southampton in the United Kingdom, “In the developing world, few if any coastal cities are prepared for the impacts of today’s extreme events, let alone climate change [and] particularly sea-level rise.”

In a 2011 research report assessing Dar es Salaam’s exposure to coastal flooding and vulnerability to climate extremes, Nicholls and colleague Abiy Kebede estimated that more than 210,000 residents, many of them poor and living in makeshift homes atop wetlands or in floodplains, could be substantially affected by sea-level-rise-induced flooding over the next 50 years.

That finding is reinforced by a more recent World Bank study examining climate change, disaster risk and the urban poor in Dar es Salaam.

Researchers determined in that study that nearly 70 percent of the city’s population lives in unplanned settlements that lack adequate infrastructure and services, and that “rapid unplanned urbanization… has led to flood risk in many informal settlements, with a wide range of associated health and other problems for residents.”

In fact, the threats to Dar es Salaam from sea-level rise are more complex than sea walls alone can resolve.

In Tanzania, as across much of sub-Saharan Africa, water and sewage management is dependent on rainfall patterns and the gravitational pull on stormwater. It goes down rivers, streams, gullies and ditches—where it can be captured, used for cooking and washing, and then released back into the watershed.

But as rainstorms intensify and seas continue to rise, the normal hydrology of low-lying districts is disrupted.

That’s because stormwater that would normally course down a watershed to ocean outfalls becomes trapped in low-lying communities, creating stagnant backwaters that breed disease while also damaging homes, roadways and other infrastructure.

At the same time, saltwater intrusion from rising seas increases the salinity of inland water resources such as water wells, rendering them unusable for drinking, cooking and washing. Spikes in salinity of groundwater are also harmful to native vegetation, causing trees and other plants to die and be uprooted, accelerating erosion and pushing communities farther from the coast.

In Dar es Salaam, this backwater phenomenon has been well-documented by the United Nations, the World Bank and other nongovernmental organizations engaged in climate adaptation and public health work.

As the U.N. Environment Programme recently noted: “Intense rainfall in Dar-es-Salaam is flooding entire neighborhoods each year. Water accumulates in the flat city, eroding the foundations of buildings. Even when residents expend all efforts keeping homes dry—sometimes permanently cementing the bottom-half of their front doors—the stagnant water erodes the outer walls and causes them to flake away.”

As a result, the United Nations, the Tanzanian government and other agencies have embarked on a parallel program to improve stormwater management through the construction of new drainage canals to help shed water off low-lying neighborhoods.

“The drainage systems have given reprieve to the waterlogged residential zones, and economic activity is now recovering on the city’s coastline,” UNEP said in a recent release.

Freddy Manyika, a project coordinator for the Tanzanian vice president’s office, said in an email that these types of climate adaptation projects have become a “national priority since the adverse impacts of climate change affects all sectors of the economy,” notably agriculture, fisheries, livestock, energy, health care, education and tourism.

Just a short drive from Barack Obama Drive, across the Kigamboni Bridge, spanning Dar es Salaam’s primary ocean inlet, one of Tanzania’s oldest private colleges is feeling the benefits of the sea wall projects. Waterfront classrooms of the Mwalimu Nyerere Memorial Academy had been vulnerable to erosion and rising seas for the past decade. The United Nations recently completed another sea wall that should protect the academy for about 60 years.

“First we were losing land. Then the buildings would have been the next to fall down,” Ukende Jonathan Mkumbo, the college’s dean of students, said in a video posted online. “The whole academy would be affected.”

Peter and Beatrice Kavishe, lecturers at the academy, noted that their campus home is now 6 feet closer to the open water than it was a decade ago. But they have gained new security with the completion of the sea wall that now stands between their home and the open water.

“It started to feel like the sea was getting a bit too close to us,” said Beatrice Kavishe. “It felt like it was closing in on us.”

The sea wall gave the school and its 5,000 students a reprieve. “To us, it is protecting our history and our heritage. Our everything,” said Mkumbo.

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.

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