Water Journal : Water Journal May 2011
feature article feature articles 46 MAY 2011 water • High water channel This involves construction of a dyked area that branches off from the main river to discharge peak flows via an alternative route. • Lowering of groynes Groynes stabilise the location of the river and ensure that the river remains at the correct depth. However, at high water levels groynes can form an obstruction to the flow of water in the river. Lowering the groynes increases the flow rate of water in the river. • Deepening the summer bed The river bed is deepened by excavating the surface layer of the river bed. The deepened river bed provides more room for the river. • Removing obstacles Removing or modifying obstacles in the river bed where possible, or modifying them, increases the flow rate of the water in the river. • Water storage The Volkerak-Zoommeer Lake south of Rotterdam provides for temporary water storage when exceptional conditions result in the combination of a closed storm surge barrier and high river discharges to the sea. Valuable Lessons to be Learned The Room for the River program is not an inexpensive initiative. Upon completion it will elevate the maximum discharge rate from the river by approximately seven per cent. If the initiatives prove cost effective, it is proposed that additional measures be implemented to raise the discharge rate to 18000m3/second by 2050. Reports of the cost-effectiveness of the initiatives may provide valuable lessons for the Dutch and for governments of other 'Delta Cities' (see Connecting Delta Cities, below). Activities in the Netherlands are not solely about building barriers or creating more room for river flow. Clever spatial planning and land use is also a vital element. For example, building structures, roads and other infrastructure on elevated land or specifically protecting that infrastructure against flooding are important elements, as are multiuse buildings; for example, a carpark now being built in Rotterdam provides both secure parking and flood storage under adjacent parkland. Floating or partially floating structures are also being considered (see Floating Houses, page 43). While all of the approaches taken recently in the Netherlands involve heavy engineering (for example, 20 million cubic metres of soil will be moved as part of the Room for the River initiative), there is an increasing focus on working with nature, rather than against it. There should certainly be important lessons learned from this effort. Connecting Delta Cities The C40 group of cities is a network of large cities dedicated to tackling climate change. Both Sydney and Melbourne are part of this body. Within the group a related cluster has been established for cities that sit on deltas and which are likely, therefore, to be more prone to the impacts of climate change, particularly sea level rise and increasing peakiness in river flows. This is known as the Connecting Delta Cities initiative. The Connecting Delta Cities goal is: "To develop a network of delta cities that are active in the field of climate-change related spatial development, water management, and adaptation, in order to exchange knowledge on climate adaptation and share best practices that can support cities in developing their adaptation strategies." According to its website the Connecting Delta Cities network will benefit delta cities through: • Exchange of adaptation strategies and best practices; • Stimulating adaptation practice and enlarging operation capacity; • Supporting the inclusion of climate adaptation in water management and spatial development; • Contributing to the image of delta cities by enhancing their vision of the future; • Raising awareness among citizens and administrations. The current Connecting Delta Cities network includes Rotterdam, Tokyo, Jakarta, Hong Kong, New York, New Orleans, London and Ho Chi Minh City. A number of other cities are potential candidates for membership. Melbourne is considering joining. More information is available at www.rotterdam climateinitiative.nl/nl/delta_cities_website/home or search on 'Connecting Delta Cities'. City of Rotterdam, host to the Connecting Delta Cities initiative.
Water Journal April 2011
Water Journal July 2011