Statistical analysis of the flood situation and assessment of the impact of diking measures along the Elbe (Labe) river

The subject of the present paper is the flood situation in the German part of the Elbe river. For this, no (international) agreement could be reached till now. Problems occur due to missing, non-plausible or uncertain flow data and due to non-stationary hydrological conditions in the basin caused by climatological variability and human impact (diking and installation of reservoirs). Regarding this complex hydrological situation a systematic procedure consisting of existing hydrological tools was developed. In a harmonised and complementary structure this procedure mainly includes the consistency analysis of flow data, statistical analyses of the flow process, especially flood statistics and their regionalisation, stochastic simulations of the flow process in the basin and flow routing. Therewith a stepwise increasingly reliable, representative, detailed and funded knowledge of the flow process may be achieved. Till now complete longitudinal sections of statistical flood parameters along the German part of the watercourse were determined for a sufficiently long period (1964-1995) best reflecting the present situation. Moreover, approximative flood statistics could be derived for a longer period (1936-1995), which may be regarded as representative for the variable hydrological conditions during the 20th century. In addition to this fundamental study the tools were applied in order to contribute to a decision support with respect to the presently discussed measures of dike shifting. The analyses revealed that a significant impact of these measures--even the impact of all measures together--on flood peaks may be achieved only if control systems at the sites of the retention spaces are used. Finally, the paper considers options of a further utilisation of the hydrological analysis results by the definition of interfaces to other disciplines.