Proving the Ecosystem Value of Natural Floodplains Through Hydrological Modelling

PROVING THE ECOSYSTEM VALUE OF NATURAL FLOODPLAINS THROUGH HYDROLOGICAL MODELLING Wolfgang Dorner2, Karl Spachinger2, Mark Porter1, Rudolf Metzka2 1 University of Southern Queensland, Australia 2 University of Applied Sciences Deggendorf, Edlmairstr. 6+8, D-94469 Deggendorf, Germany [email protected] Abstract Ecosystems provide valuable functions. Also natural floodplains and river structures offer different types of ecosystem functions such as habitat function, recreational area and natural detention. From an economic stand point the loss (or rehabilitation) of these natural systems and their provided natural services can be valued as a damage (or benefit). Consequently these natural goods and services must be economically valued in project assessments e.g. cost-benefit-analysis or cost comparison. Especially in smaller catchments and river systems exists significant evidence that natural flood detention reduces flood risk and contributes to flood protection. Several research projects evaluated the mitigating effect of land use, river training and the loss of natural flood plains on development, peak and volume of floods. The presented project analysis the hypothesis that ignoring natural detention and hydrological ecosystem services could result in economically inefficient solutions for flood protection and mitigation. In test areas, subcatchments of the Danube in Germany, a combination of hydrological and hydrodynamic models with economic evaluation techniques was applied. Different forms of land use, river structure and flood protection measures were assed and compared from a hydrological and economic point of view. A hydrodynamic model was used to simulate flows to assess the extent of flood affected areas and damages to buildings and infrastructure as well as to investigate the impacts of levees and river structure on a local scale. These model results provided the basis for an economic assessment. Different economic valuation techniques, such as flood damage functions, cost comparison method and substation-approach were used to compare the outcomes of different hydrological scenarios from an economic point of view and value the ecosystem service. The results give significant evidence that natural detention must be evaluated as part of flood mitigation projects. In addition can be stated that the loss of detention due to land use and dikes can be called an externality and results in economic inefficiencies. Keywords: Ecosystem value, natural detention, externalities. 1 INTRODUCTION Our environment provides different services and functions we are using on a daily basis. But what happens if we destroy these functions or restrict their ability to provide the services? Since Kyoto it is not new that also environmental problems are threats to our economy and destruction of environmental functions result in economic damages. Most of these services can be measured in economic terms as benefits or their loss as economic damages. To describe these effects requires a deep understanding of environmental dependencies and the knowledge how to value the results in economic terms. In different fields these approaches have been tested. The Kyoto Protocol is one of the applications where the interaction of environmental economics and scientific modeling resulted in a global approach to protect the environment. Especially with regard to water it is a major concern that natural measures and the protection of the environment is confronted with economic considerations. This includes always the thought that nature stands besides economic interests. This paper does not propose a methodology to “economize” our environment, but provides a methodology and delivers evidence why it is economically necessary to protect riverine landscapes and catchments. It is an approach to couple hydrological and hydrodynamic models and economic analysis to quantify the amount of ecosystem services provided by natural river systems and flood plains and express it in monetary terms. As a form of ex ante analysis the proposed methodology can help to derive economic arguments to protect riverine landscapes. From an ex post point of view and as part of flood protection studies it provides economic arguments for river renaturalisation projects and dike re-allocations to increase the flood plain. Results of the chosen approach can be used in cost-benefit analysis or cost comparison analysis to provide a more complete economic picture of planned activities. 2 ECONOMIC THEORY Different forms of water use like fresh water or sewage fees already show that in some cases water or water related services are valued. But in some cases these instruments seem to miss or fail. Water use or the use of water bodies can be subdivided into: direct and indirect use. Direct use includes all types of use where water becomes directly part of the product or is used in the process of production. Indirect use sums up all effects, where water is influenced as a side effect of the production, where the water “use” has no direct impact on the success or failure of the production process and the resulting product. Examples of direct uses are hydropower, farming in connection with irrigation or washing water for vegetables. A typical form of indirect use is erosion on agricultural sites. Excessive rainfall does not play a role for the success of agriculture. During such events most rain water is lost, because of low infiltration and fast surface run-off. But through erosive processes because of agriculture and the transport of sediments, nutrients and pesticides the farming process influences the water bodies. Water can be used physically and chemically. A typical form of physical use of water is hydropower. The elevation energy of water is transformed into motion energy in a turbine, which is transformed to electricity. In sewer systems the transport capacity is used to remove sewage and waste. In power stations water is used to cool the system or transfer heat energy via steam to drive turbines. Classical chemical uses are the ability of water to serve as a solvent, either for other chemical substances (colouring, nutrition,...) or for detergents to remove dirt. A discussion about the use of water should evaluate also two different forms of use: 1. Consumptive use like for irrigation or thermal power station cooling 2. modifying uses such as discharge of waste water Dyck (1995, p. 82) names the main functions of water bodies as: • self-purification, • biological potential yield, • ecologic potential, • transport of material (solids or solved materials), • potential energy (kinetic energy, heat capacity), • recreational use and • flood routing. We can use a scientific classification scheme for the use of water, water bodies and ecosystems: • Physical use, like gravitational energy, flow energy, transport capacity for subspended • and solid substances and temperature. • Chemical conditions like solvent for substances and fluids. • Biological conditions, like self cleaning capacity. This means that the direct use of water e.g. as potable water or for irrigation is only one of several use types or use function aquatic ecosystems provide. Emmerton (2005) distinguishes between direct values (production and consumption goods), indirect value (ecosystems functions and services), option value (potential for future use), non-use value (like heritage value, cultural value, …). It is not only of importance to look at the use of water itself, but also the functions water bodies provide. Technical intervention and human actions in general do not only use the resource water, but lead to severe damages and irreversible changes in our enviroment. ``Wasser wird heute zumeist als eine unter vielen Ressourcen angesehen, die für die wirtschaftliche Entwicklung eines Landes notwendig ist und die sich für diese Zwecke nach Belieben aufstauen, umleiten und vermehren läßt. [Today water is seen as one of many resources, necessary for the economic development of a country and that can be detained, redirected and increased for this purpose.]'' (Wallacher 1999, p. 165) “Natural ecosystems yield a wide range of goods and services, many of which are related to either their demand for water or their role in water supplies, and most of which have an extremely high economic value” (Emerton 2005, p. 3). Daily (1997) points out that “Ecosystem services are the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life.” Ecosystem valuation can be seen as a method to make peoples preferences to pay for ecosystem services visible. Using this valuation technique allows to make ecosystems or their services comparable to other goods and sectors (Emmerton 2005, p 3). Emerton (2005) gives an overview of the benefits of wetlands. As part of the study “Integrating wetland economic values into river basin management” 12 projects from different continents are presented and evaluated (Emerton 2005). Different functions of wetlands were identified and valued with regard to their economic value e.g. water purifaction, habitat and food reserve or flood detention. From an economic point of view the relevant factor in decision making can be reduced to the well being of individuals or society. Cost-benefit analysis as an evaluation technique to compare different situations is based on this concept. The situation where the welfare, well-being or utility of an economic actor in a situation A is higher than in situation B would result in the preference for situation A. Preferences

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