Central innovation theme of the city of tomorrow
A functional infrastructure creates the foundations of urban life. It protects us from disasters, ensures healthy living conditions and forms the backbone for the performance of our economy. We need roads, paths and railways to get to work, for daily errands and during leisure time. It is not only companies but also private households that are increasingly dependent on urban goods logistics. Underground pipelines and networks supply us with water, electricity and heat, enable telecommunications and media services, and ensure the drainage of rainwater and wastewater.
The construction of infrastructure is costly. Once built, the infrastructure shapes the city for decades or even centuries. The construction of infrastructure thus not only determines the quality of the city today, but also the possibilities for achieving better quality in the future. Examples are street spaces that allow for a change in mobility, supply and disposal structures that allow for an adaptation to more sustainable energy sources, and an infrastructure design that can also cope with future climate and environmental challenges. In HafenCity, this was already evident at an early development stage in the relevant measures relating to flood protection.
HafenCity Hamburg GmbH therefore integrates infrastructure planning closely with the other aspects of urban development and itself acts as the developer for public transport facilities, bridges, parks, squares and promenades. This allows for development on a scale in line with needs and implementation timed to fit with private construction projects. In addition, the planning and construction of infrastructure provides an important technological lever for making urban development more sustainable.
Building by the water
HafenCity sees Hamburg’s city center growing from the waterside location by the Alster that previously characterized it to the main channel of the Elbe’s northern arm. This brings with it particular challenges in terms on infrastructure – especially the creation of resilient flood protection measures that anticipate climate change and the safe construction of infrastructure and buildings on the soils of the Elbe flood plain with their low load-bearing capacity. Without the solutions adopted, the sustainable conversion of the former port area for inner-city living, working and leisure would not be possible.
Building on the poor load-bearing ground close to the water has a long tradition in Hamburg. The upper layers of soil are made up mostly of clay and glacial sediment. Sand, which is load bearing, begins further down. This is why pile foundations are used for buildings in many parts of the city. Buildings are constructed on piles driven into the earth, which transfers the weight from the upper layers to the deeper load-bearing sand layers. In HafenCity these piles are about 20 m long as a rule.
For roadbuilding, laborious pile foundations can usually be dispensed with. Here the high load-bearing capacity of the piles is not always necessary. It is sufficient to preload the surface so that water is pressed out of the upper soil layers, compressing and stabilizing them. Several years before future roads are finally surfaced, up to 8 m of sand is temporarily packed on them. Vertical drainage speeds the removal of water.
Water is a challenge not only when it comes to subsoil. Despite being more than 100 km from the open North Sea, the valley of the Elbe around Hamburg is strongly exposed to the forces of the tides. The inner city and other parts of the city sited on the Elbe marshes are protected from flooding by dikes. In the port of Hamburg it is different. It is located outside the line of Hamburg’s main dike. Port operations benefit from their direct access to the water and instead protect themselves on a site-specific basis with various technical and structural measures. In the event of a severe storm surge, where site-specific measures are insufficient, those employed on site leave the port. In urban areas where people live or stay overnight, this approach is problematic. Even in an emergency or at night, residents must be able to access medical care safely and be reached by rescue workers and firefighters.
Even before construction work on HafenCity began, it was necessary to clarify how the former industrial and port area, lying at 4.5 to 5.5 m above mean sea-level (MSL) could be permanently protected. A conscious decision was taken not to surround the whole area by dikes. Enclosure of the site by dikes would have had to have been completed before any construction of buildings began. This would have significantly delayed the start of development and placed a considerable burden on the public purse. Locks would have been necessary to keep the enclosed channels navigable. In addition, dikes would have represented the maximum ecological intervention in the Elbe floodplain. Its flows and tidal development would have deteriorated. And a dike would also have completely deprived the site of the proximity to water that is today such a feature. There would have been no generous waterfront spaces.
The “Warft” model
As an alternative to dikes HafenCity has fallen back on the settlement pattern traditional in the North Sea area, the “Warft”. A “Warft” is an artificial mound that protects a settlement in the marshes from rising water. In HafenCity this “Warft” is created by building new streets at a raised level of 7.5 to 8.5 m above MSL. There are synergies here with road construction, because some of the sand added to compact the upper soil layer can remain as the new road base. Service mains can also be accommodated in the layer of sand.
Building plots do not need to be raised. Instead of a basement story an artificial base is built, usually on a level with the historic port. The exterior wall of the plinth is built to be watertight. To retain access to the water and the characteristic historic quay walls, with a few exceptions buildings are not constructed right up to the water’s edge. This creates 10.5 km of new waterside promenades at the historical port level. Where the plinth level abuts a promenade, it will be accessible at ground level. Flood gates or comparable technical equipment protects the restaurants and stores located in the plinths. Above the plinth level, the first floor is level with the sidewalks on the streets. The resulting topography characterizes the cityscape of HafenCity.
The “Warft” model protects HafenCity’s residents, workers and visitors even in the case of severe flooding. Even during the strong storm surges that occur about twice a year today, city life on the “Warft” can continue largely unaffected. The promenades are only flooded for a brief period. The solution applied also retains the water level’s dependence on the tides and the resulting special character of the city districts on the Elbe. This is of particular importance for the canals of the Speicherstadt UNESCO World Heritage Site. However, the Speicherstadt, which remains at its historic level, separates HafenCity’s plinths from the parts of the city center protected by the main dike line. To ensure that HafenCity is accessible to emergency services and law enforcement even in the event of extreme flooding, the bridge structures in HafenCity are also of particular importance for flood protection.
As an island situated in the north arm of the River Elbe, HafenCity depends on bridges to connect with the outside world. External connections are thus doubly important for HafenCity. On the one hand, the flood protected bridge links to the north ensure access by emergency service vehicles even in the case of flooding. On the other, everyday routes are what integrate HafenCity with the neighboring districts of the Altstadt and Neustadt to the north, Hammerbrook and Rothenburgsort to the east and Veddel and the new innovation district of Grasbrook to the south.
The Kibbelstegbrücken opened back in 2001 represent a first infrastructure milestone in the development of HafenCity. They were the prerequisite for planning permission for residential buildings on Sandtorkai. They are normally used for pedestrian traffic only, but can also provide access for emergency service vehicles if necessary. The line of three bridges over the Zollkanal and through the Speicherstadt complement the existing bridge links over the Zollkanal between the Altstadt and HafenCity. Today, four road bridge links and four further footpath and cycle path links connect HafenCity with Hamburg’s existing city center neighborhoods.
As the structural development of HafenCity progresses and work begins on the Baakenhafen and Elbbrücken quarters, the focus is shifting to integrating HafenCity with the neighboring districts to the east and south. For example, a new pedestrian and cycle link will be created between HafenCity and the Entenwerder Elbpark. Further bridge links across the Oberhafen Canal and the Norderelbe are at the planning stage.
Bridges are also important within HafenCity, which is crisscrossed by a multitude of former harbor basins, closely connecting the various neighborhoods. Today, for example, Busanbrücke is the most important bridge for pedestrians and cyclists in central HafenCity. In terms of design, it is part of the square in front of the International Maritime Museum and, as a former road bridge with a new surface and benches, has great amenity value.
Two bridges connect the northern part of the Baakenhafen neighborhood with the southern part. The 170 m long Baakenhafen Bridge, opened in August 2013, is outstanding in many respects. On the one hand, it is a road bridge from which the middle bridge element can be removed for water traffic with the help of the tide, and on the other hand, it is a much-frequented place to spend time. The special bridge design shields traffic noise and allows a special panorama of the Elbe, the harbor and central HafenCity. The crossing is supplemented by the central pedestrian bridge between the northern part of Baakenhafen quarter and the Baakenpark peninsula, which also carries all the supply and disposal mains for the southern part of the neighborhood. The mains could not be routed along the road as usual due to the removability of the central bridge element of the Baakenhafen bridge.
HafenCity has an extensive mobility infrastructure with a wide range of different mobility options. The goal of its smart mobility concept is to reduce the need to use private cars and instead to encourage the use of public transport, in particular, as well as active mobility on foot or by bicycle. Probably the most important contribution to sustainable mobility behavior is the close-knit network of footpaths and cycle paths along the streets and through public spaces. Together with the fine-grained mix of uses, the activation of street level areas and the intensive density of uses, it contributes significantly to shortening individual journeys for work, shopping or leisure.
Streets in HafenCity, whose space allocation between roadway, cycle lane and sidewalk has shifted in favor of the ancillary areas important for pedestrians and cyclists, retain a central development function. On the one hand, the important supply and disposal mains lie beneath the road. In HafenCity, this includes a separate system for rainwater and wastewater, which ensures that polluted and clean water are channeled away separately – even in the event of flooding. The rainwater on roads and bridges is also cleaned before being introduced into the storm drainage system. On the other hand, roads also retain an important traffic access function. In the event of an emergency, for example, every building must be accessible to firefighters and ambulances. Prior to the construction of the final roadway surfaces, pedestrian and cycle paths, tree planting and parking bays, the roads are mostly laid out temporarily. This avoids impacting the final design during construction activities.
The fact that vehicle accessibility can be combined with traffic calming is shown, for example, by the street Am Lohsepark. The street on the west side of the park is designed as a bicycle boulevard. The low curb creates a soft demarcation between slower pedestrians and faster cyclists, who can mix on the street surface in certain cases. Other neighborhood streets are designed for mixed traffic of cyclists and cars. Here, the street design generally provides for slower travel, but still allows for regular bus services.
In addition to their access function, the main roads in HafenCity also fulfill a higher-level function in Hamburg’s road network. Due to its location between the city center and the Elbe bridges, HafenCity also has to carry some of the traffic coming from the Süderelbe area. It has been possible to concentrate this through traffic on a few four-lane road corridors. Along the main thoroughfares, cyclists are routed along separate cycle lanes or cycle paths throughout.