New Infrastructure – Basis of this Urban Development
Proximity to water, ground conditions and flood risks present particular challenges
A whole new infrastructure has been built for the HafenCity (© ELBE&FLUT) Start slideshow
HafenCity is characterized by infrastructural features specific to the site: the area is a low-lying island in the River Elbe, indented by several harbor basins. Prerequisites for urban use are therefore new internal and external connections and cross-links as well as flood protection.
One challenge is the east-west orientation of the historic warehouses in the Speicherstadt, which act like a barrier between HafenCity and the City as well as the waterways, which also extend east-west. These factors meant, for instance, that efficient public transport connections could only work well underground via subway.
Furthermore, the HafenCity site is situated outside Hamburg’s dike line on low-lying land not protected from flooding at 4 to 5.5m above sea level. Because of its location in the Elbe, separate and costly protection measures are required: HafenCity hugs the Elbe for more than 3.1km and has a total waterfront, including harbor basins, of over 10.5km.
In its past, the HafenCity area was characterized by its use as an industrial and port district. The extension of the modern port facilities that began in 1862 gave this area the typical appearance which largely remains today, with harbor basins and docks constituting Hafen- City’s character.
In many places, Am Sandtorkai/Dalmannkai, for instance, the historic quay structure could be partially conserved and carefully restored. New quay walls were built in sections where the old substance was too damaged or previously did not exist. Since the area’s industrial uses left traces, highly contaminated soil on a number of sites had to be cleaned.
FLOOD PROTECTION HAS TOP PRIORITY
Flood protection was, and remains, an important precondition for building HafenCity. There was a conscious decision not to surround it with dikes. Works would have had to be completed prior to realization of the first buildings throughout the new district’s 128 hectare land area. A speedy start to HafenCity’s development would therefore not have been possible and, at the same time, dike construction would also have generated significant front-end costs. From a built environment standpoint, dikes would have precluded HafenCity’s unique waterfront characteristics.
Instead, new buildings – and streets – are built on elevated mounds at a new level of 8-9m above mean sea level, protecting the development from floods. They also offer space inside for flood-secure parking garages. In contrast, promenades and certain squares remain at the area’s previous elevation of about 4.5 to 5.5m above sea level, which attractively preserves their close links to the water and allows creation of useful public spaces of high quality.
An additional challenge is the clay soil. HafenCity’s location on the Elbe marshes is subject to the alluvial influence of the Elbe, which means that the upper layers of soil are made up mostly of clay and glacial sediment. As so-called cohesive layers, they are highly water absorbent, which means they cannot bear heavy weight. Sand, which is load-bearing, begins further down. This is why all buildings in HafenCity are built on piles. These are usually driven around 20m deep into the earth, which transfers the weight to the loadbearing sand layers. For road building, preloading is used to raise the level to 10m: the weight of heaped up sand presses any water out of the cohesive layers of ground below, creating a stable foundation suitable for road-building. When this process is finished, the sand preload is removed down to around 7.5 to 8m, the future level of the road, so that piping and conduit can be laid and roads built.