HAMBURG LETS THE WATERS IN...

Container ships navigating the Elbe upstream from Hamburg (Fabian Bimmer/Reuters)

 

In response to rising tides, the city will give its river some much-needed space to breathe...

When it rains hard enough, large tracts of Hamburg can easily end up under water.

It’s a situation that’s becoming more common in cities around the world, but to some extent it’s always been true in Germany’s second largest city, made vulnerable by its partly low-lying location at the tidal mouth of the River Elbe. Just last month, the city’s Fish Market ended up inundated by high water. With sea levels rising, such floods risk getting more frequent and more damaging, and Hamburg needs to act. It’s already doing just that, with a huge scheme to raise 103 kilometers of the levees around the city by 80 centimeters (2.6 feet) to keep rising tides and seasonal high waters at bay.

But this is more than simply building the river walls higher, which will happen gradually between 2020 and 2050. The city’s other weapon against rising tides is much more in tune with nature. By building the walls farther inland than where they stand today, the plan will create a new floodplain of water meadows to act as a sponge when the river spills over. This will allow the Elbe’s waters to safely breach their banks without causing destruction, relieving pressure elsewhere and helping to restore a more natural appearance to this heavily exploited waterway. Simply put, instead of shutting the waters out, Hamburg will find a way to make room for them.

Force a river or sea into ever higher, tighter walls and you risk merely displacing a flood to create destruction elsewhere.

This new floodplain could kick-start the process of restoring some natural balance to a dockland area under severe stress. Over the past 50 years or so, large sections of Hamburg’s port have been deepened to accommodate container ships. This process has kept some jobs in the city, but it has come at an ecological price. Deepened channels have encouraged the tides to sweep further down the river mouth, pushing the freshwater zone—and the flora and fauna that thrive there—further inland and turning the waters more brackish. Riverine wildlife has been pushed into retreat.

The floodplain plan could, if expanded, mark a turning point for the estuary, reintroducing environments for wading birds and marshland plants that would give the river an authentically lush, ragged fringe. The land itself could still be used as pasture, meanwhile, provided animals were removed at the threat of flooding. Water meadows were traditionally used for dairy farming because, while flooding often made them unsuitable for crops, their heavy deposits of river silt made the grasslands especially vibrant and varied in plant life.

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Is Hamburg’s plan for a greener, less impregnable river bank the shape of things to come? This bright idea sounds like common sense, but it could still prove hard for others to emulate. Most cities of this size (1.7 million people in the city, 5 million in the wider metro area) simply don’t have this kind of spare land that they’d be open to flooding.

Hamburg itself has struggled to get the plan even to this point: one potential site has already been rejected because it was divided among too many private owners. Luckily, it has still found an isolated 20-hectare (50 acre) site, part of a large semi-urban island just upstream from the city (the rough location of which is viewable on Google maps here) that was previously used as a dumping ground from sediment dredged from the region’s waterways. This type of site still poses a challenge. The dredged silt of a busy industrial port isn’t the purest of substances and the area may need substantial cleaning before the Elbe’s waters are allowed near it once more. Once the new levee is built behind the site, the old dyke protecting this 20 acre patch can be dismantled, leaving it still available as pastureland or for leisure at any time but during periods of high water.

Cleaning up this pollution is a reward in itself, of course, while the enlightened attitude to flood management is exemplary. Force a river or sea into ever higher, tighter walls and you risk merely displacing a flood to create destruction elsewhere. Let a swollen river breathe out into a broader landscape, and you create an environment that can ultimately be safer and greener—and altogether more beautiful.

Feargus O'Sullivan

Feargus O'Sullivan is a London-based contributing writer to CityLab, with a focus on Europe.

source: https://www.citylab.com/

original story HERE

 

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