Planning practice in support of economically and environmentally sustainable roads in floodplains: the case of the Mekong delta floodplains.

Road development in relatively undisturbed floodplain systems, such as the floodplains of the Mekong River, will impact hydraulics and interrupt the natural flow of water. This affects the ecology and environment, and the livelihoods of people who depend on fishing and agriculture. On the other hand, floods can severely damage road infrastructure in years with large floods and can cause high annual maintenance costs. Improving road development practices in floodplains is a complex, multidimensional task involving hydraulic and geotechnical analysis, ecosystem analysis, socio-economic analysis, policy analysis, etc. This paper analyses the planning practice of road development and rehabilitation and how this practice can be improved in support of economically and environmentally sustainable roads in floodplains. It is concluded that although ample technical, planning and environmental assessment guidelines exist, guidelines need updating to address cumulative impacts at floodplain level and factors hampering the implementation in guidelines should be addressed in the guideline design (process).

Quantifying ecosystem service trade-offs: the case of an urban floodplain in Vienna, Austria.

Wetland ecosystems provide multiple functions and services for the well-being of humans. In urban environments, planning and decision making about wetland restoration inevitably involves conflicting objectives, trade-offs, uncertainties and conflicting value judgments. This study applied trade-off and multi criteria decision analysis to analyze and quantify the explicit trade-offs between the stakeholder's objectives related to management options for the restoration of an urban floodplain, the Lobau, in Vienna, Austria. The Lobau has been disconnected from the main channel of the Danube River through flood protection schemes 130 years ago that have reduced the hydraulic exchange processes. Urban expansion has also changed the adjacent areas and led to increased numbers of visitors, which hampers the maximum potential for ecosystem development and exerts additional pressure on the sensitive habitats in the national park area. The study showed that increased hydraulic connectivity would benefit several stakeholders that preferred the ecological development of the floodplain habitats. However, multiple uses including fishery, agriculture and recreation, exploring the maximum potential in line with national park regulations, were also possible under the increased hydraulic connectivity options. The largest trade-offs were quantified to be at 0.50 score between the ecological condition of the aquatic habitats and the drinking water production and 0.49 score between the ecological condition of the terrestrial habitats and the drinking water production. At this point, the drinking water production was traded-off with 0.40 score, while the ecological condition of the aquatic habitats and the ecological condition of the terrestrial habitats were traded off with 0.30 and 0.23 score, respectively. The majority of the stakeholders involved preferred the management options that increased the hydraulic connectivity compared with the current situation which was not preferred by any stakeholders. These findings highlight the need for targeted restoration measures. By that, it is recommended that additional measures to ensure reliable drinking water production should be developed, if the higher connectivity options would be implemented. In the next step it is recommended to include cost and flood risk criteria in the decision matrix for more specific developed measures. The research showed that pair-wise trade-off figures provided a useful means to elaborate and quantify the real trade-offs. Finally, the research also showed that the use of multi criteria decision analyses should be based on a participatory approach, in which the process of arriving at the final ranking should be equal or more important than the outcome of the ranking itself.

Ecosystem services assessment of two watersheds of Lancang River in Yunnan, China with a decision tree approach.

In the Langcang (Upper-Mekong) watershed, degraded watershed ecosystems in upland areas threaten cultivation practices, water resources, and dam development downstream. Assessment of ecosystem services and the factors that threaten them is an important first step to support watershed management. This, however, requires detailed information that is often missing in mountainous regions. To overcome this, in this paper, we adopt a decision tree approach to assess protection, biodiversity, and production services in two mountainous watersheds (Fengqing and Xiaojie) of the Lancang River Basin. Decision tree rules were built on the basis of field surveys, available references, ecosystem maps derived from remote sensing, expert knowledge, basic topographic information, and community interviews. Decision tree results showed that forest cover and agro-forestry practices contribute greatly to improved ecosystem functioning in the Fengqing Catchment compared to the Xiaojie Catchment. The results were consistent with field observations. The decision tree method proved to be a suitable and flexible tool for the rapid assessment of watershed ecosystem services, for highlighting those areas that need more in-depth research, and for guiding watershed and ecosystem management.