Thoughtful Water Management
The North Rhine-Westphalian city of Kamp-Lintfort in Germany shows what future-oriented urban and settlement development can look like, taking into account water-sensitive streetscape design with near-surface drainage.
The increase in sealed surfaces in recent years has significant effects on the water balance of cities and municipalities. Consequences such as the reduction of groundwater recharge, a changed local climate due to a lack of evaporation as a result of surface runoff and the dangers of flood peaks present new tasks for transport planners. These after-effects of the already existing sealing are favoured by the constant expansion of road traffic areas, a growing demand for settlement areas and the predicted, if not already existing, climate change. The urban land use planning of the city of Kamp-Lintfort shows what future-oriented urban and settlement development can look like.
Laying the foundations, planning carefully
Even before the development plan came into force, an expert opinion on the seepage capacity of the subsoil was commissioned for the unused green space "Volkspark" in Kamp-Lintfort. This was to provide information on the building ground, the possible type of infiltration and the construction of the infiltration facilities. Several percussion coring boreholes, each to a depth of 4.0 m, provided information on the permeability coefficient of the subsoil. Furthermore, it was found that groundwater was not present up to the final depths of maximum 4.0 m below ground level. The results of the investigations showed subsoil conditions that permit infiltration of the precipitation water via pipe trenches or trough trenches in accordance with DWA worksheet A 138 ("Planning, construction and operation of facilities for infiltration of precipitation water") in the permeable, clay-free sands. Thus, nothing stood in the way of planning and implementing decentralised infiltration of the precipitation water on the properties in accordance with § 51a of the NRW State Water Act (as of 2009).
The infiltration of surface water into swales is both ecologically and economically preferable to direct discharge into the sewage system.
Drainage of surface water through pipe systems into the swale.
Showing the water the right way
Rainwater management in urban areas places high planning demands on municipalities. At the same time, there are extensive opportunities for urban and open space design and the reduction of flooding risks in buildings and infrastructure (flood prevention). In recent decades, attempts have been made to channel rainwater into the sewage system as quickly as possible. Today, the infiltration of water on the property or in public areas and the creation of retention areas should be the primary goal.
In order to prevent surface water from finding its own way, constructions are necessary that ensure targeted, rapid drainage. These can be curb channels, box channels or slot channels that keep the water away from the road and drain it away safely.
Drain safely and quickly
In the course of the drainage planning for the traffic areas in the construction area, a roadside drainage system was planned that had proven itself in Kamp-Lintfort. The drainage channel system MAXI was used. Depending on the hydraulic performance requirements, channel elements with four different nominal widths (100 to 300 mm) were installed.
Eight safety points per running metre absorb and transfer e.g. braking forces in the longitudinal direction. Anchoring ribs to prevent "floating" and preforms for vertical drains DN 100/150 complete the advantageous properties of the drainage channel system MAXI.
The installed roadside drainage also takes over the task of street drains in the new residential development area. The water enters the short sewer pipes via the drainage channels and a feed box, which ends in the swale.