University of Twente Student Theses


Evaluation of streamflow and ensemble tresholds

Weeink, Werner H.A. (2010) Evaluation of streamflow and ensemble tresholds.

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Abstract:The use of ensemble weather predictions in flood forecasting is an acknowledged procedure to include the uncertainty of meteorological forecasts in streamflow predictions. Flood forecasters can thus get an overview of the probability of exceeding a critical discharge, and decide on whether a flood warning should be issued or not. This offers several challenges to forecasters, among which: 1) How to define critical thresholds along all the rivers under survey? 2) How to link locally defined thresholds to simulated discharges, which result from models with specific spatial and temporal resolutions? 3) How to define the number of ensemble forecasts predicting the exceedance of thresholds necessary to launch a warning? In this study, streamflow thresholds are investigated for 75 catchments in France with defined operational thresholds. The emphasis lies on exceedances of this streamflow threshold -based on instantaneous observations- by daily discharges during a period of 10 years. The analysis shows that there is an overall optimal tradeoff among hits, misses and false alarms, expressed by the Critical Success Index (CSI), when the instantaneous streamflow thresholds are multiplied by an adjustment factor of 0.90 to give the daily streamflow thresholds
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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