Devastating floods in various regions of the world in the past decades have posed old questions regarding whether these floods were caused or aggravated by river regulation works carried out to improve the navigation.
rnrnThe large number of severe floods on almost every continent during the past decade has resulted in increased awareness of planning and preparation of flood defence and protection measures, leading to a revision in flood management philosophies. The common practice now seems to be: ?give the rivers more room?. Flood management measures, such as flood channels or lowering of summer embankments, may influence the flow pattern in the main channel during non-flood conditions. Lowered water levels or sedimentation in the fairway might hamper navigation or require costly measures (like dredging). ?Room for the river? projects often also aim at increasing ecological bio-diversity, so elements of growing vegetation, side channels and undefended banks are re-introduced in the (regulated) river systems, which may have impact on flood levels and navigation. The increasing amount of flood management projects in preparation along many rivers that are also important inland water transport (IWT) routes, make it necessary to deal with negative effects of flood management works on navigation and vice versa.
rnrnProtection against floods is a basic need for every society, and its importance increases with growing population and prosperity. In many countries, rivers are of vital importance for navigation, in fact many countries owe their prosperity partly to the development of IWT along these rivers. The increased activity emerging from both policy fields (flood management and navigation) presents an opportunity for integrated approaches that address both needs.
rnrnBecause of the relation of navigation to flooding, the environmental commission of PIANC established a working group to study the possibilities of a sustainable development strategy for both navigation and flood protection. PIANC views that the need for further development of water borne transport and navigation can only be achieved in a sustainable way and in accordance to the improvement of flood protection.
rnrnRiver regulation by means of training works provides a stable riverbed and a regular fairway. During flood conditions, the flood wave may also be affected, travelling downstream with a higher velocity and peak level. Planners of both flood management and IWT projects should be aware of this side effect, and consider alternative or mitigating measures. Because IWT is regarded as an environmentally friendly mode of transport in many countries and is politically well accepted, IWT-projects are of importance. As a consequence, the relationship between IWT and flood conditions must be dealt with very carefully.
rnrnIn this report five criteria for sustainability are used:
rnrn1. preservation of ecological functions;
rn2. considering system impacts;
rn3. regard economical sustainability;
rn4. use reversibility of measures and effects;
rn5. enlarge resilience of the river system.
rnrnFloodings are determined by the meteorological and hydrological situation, the topography and the use of the riverbed and floodplains. This report concludes that if measures are adopted using a system-approach to river-basins, most of the navigation measures do not affect flooding and only have a local effect. And that in this case most flooding measures do not affect navigation measures. To jointly develop navigation and flood protection improvements in a sustainable way, it?s crucial to:
rnrn1. adopt a comprehensive system-approach of the water basin, based on a long term vision;
rn2. take into account all related interests and stakeholders, and use an adequate organisation and management of the planning;
rn3. adapting the relevant sustainability criteria.
rnrnAn integrated approach avoids unexpected negative impacts on the river system, ecology and society. A framework for an integrated approach is presented, in which seven steps are discerned: System analysis, Measure identification, Selection, Strategies, Impact assessment, Optimization and Mitigation, Choice. Letting stakeholders participate from the beginning, while developing the plans, avoids resistance and improves acceptance of the measures.
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