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Speaker: Zbigniew Kundzewicz
zbyszek<at>pik-potsdam.de
Research Centre of Agricultural and Forest Environment, Polish Academy of Sciences,
(PAS), Poznan, Poland; (PIK, Germany)
Title of the talk: Management of water-related disasters (pdf: 2,9 Mb)
Summary of the talk by a student: Students´
summary (pdf)
Introduction to the problem area of water-related disasters and their management will be given. Even if the understanding of the notion „water-related disasters” may embrace extreme cases of all three categories of water problems, i.e. too little, too much, too polluted, the scope of the lecture will be restricted to the situations of disastrous abundance and deficit of water, i.e. floods and droughts.
Floods and droughts are natural phenomena of major concern since the dawn of human civilization. Vulnerability to floods and droughts has grown, and continues to grow, due to the increasing exposure and insufficient rise in adaptive capacity. Discussion of extreme hydrological events in the context of driving forces, pressures, states, impacts, and responses will be presented. A review of factors responsible for increase in the risk and vulnerability will be offered.
Mechanisms of both types of extreme hydrological events will be explained in reference to the river flow process, based on simple, idealized concept of rainfall-runoff system. This example illustrates the basics of the mathematics of extreme hydrological events, and possible interpretation of the notions of risk, vulnerability, and resilience, based on the threshold crossing (excursion) theory. Discussion of simple concepts of water storage will help gain insight into a powerful remedy against both floods and droughts. The issue of quantifying droughts and floods will be tackled.
Taxonomy of floods and droughts will be discussed. Among categories of the former are - flash, lowland, rain-caused, snowmelt, ice jam, flow obstruction, dam break floods, and storm surges. The notion of drought may embrace meteorological drought, agricultural drought, and hydrological drought. It is worth stating that hydrological drought can be natural (caused by scarcity of precipitation and high evapotranspiration due to high temperature), but it can also be entirely man-made, due to overabstraction and mismanagement. Hence, droughts should not be viewed as exclusively physical or natural phenomena, but as a product of interaction between natural conditions and human activities (leading to water withdrawals and consumption).
Brief overview of a sample of disastrous recent events in Europe will be given and projections for the future, driven by climate change scenarios will also be presented. It is foreseen that the climate change may lead to amplification of water-related extremes. Increase in intense precipitation, which is a sufficient condition for flood hazard rise, has been observed already and is foreseen for the future. Increase in severity of summer droughts in continental interiors has been a robust result, across several scenarios and models. This worsens the problems likely to result from the population rise. Hence, the 21st century has been baptized the age of water scarcity.
Review of policy responses to extreme hydrological events will be offered, including discussion of strategies: protect (as far as technically and financially feasible), accommodate (live with floods), or retreat. A few case studies of policy responses to floods and droughts will be discussed. Structural measures will be reviewed and probabilistic design of flood protection measures (dams, levees) in the changing world will be discussed. A review of related concepts, such as flood frequency analysis, intensive precipitation records, duration – intensity – frequency in a point and areal sense, will also be presented. Non-structural measures will be reviewed, embracing forecast – warning – response – evacuation system, loss potential and inundation risk mapping, insurance, legislation, etc. Response policies will be regarded in the sustainable development context. Catchment management (source control), according to the rule: “keep water where it falls” is perhaps the most advantageous option.
It is a general observation that floodplains in Europe have been developed (drained and converted to agriculture and settlements) and are being further developed. Hence, highly valuable natural floodplain habitats have been degraded. On the other hand, encroachment of humans into floodplains proved to lead to increase in flood risk, since structural defenses cannot offer complete protection, failing in case of extremely high floods. Re-establishing floodplains offers interesting opportunities and co-benefits for: (i) flood protection and (ii) conservation or restoration of valuable wetlands (subject to natural flood pulse). One of the most valuable ecological services of floodplains is the disturbance reduction, enhancing water storage, beneficial for both floods and droughts.
The lecture will include presentation of research results from PIK and PAS. Its objectives will be to provide information, to enhance understanding, and to provoke thoughts.
Suggestions for students’ work
Designing storage (determination of necessary storage capacity; checklist of important items)
Management of extreme events – Quo vadimus? Filling questionnaires (prepared in advance by myself) individually. Group work towards a collective and consolidated reply to questionnaire. Consensus building process (with eventual votum separatum noted).
Recommended background literature on this presentation:|
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