Abstract
Abstract. The objective of this paper was to describe the impact of climate change on the Mississippi River flood hazard in the New Orleans area. This city has a unique flood risk management challenge, heavily influenced by climate change, since it faces flood hazards from multiple geographical locations (e.g. Lake Pontchartrain and Mississippi River) and multiple sources (hurricane, river, rainfall). Also the low elevation and significant subsidence rate of the Greater New Orleans area poses a high risk and challenges the water management of this urban area. Its vulnerability to flooding became dramatically apparent during Hurricane Katrina in 2005 with huge economic losses and a large number of casualties. A SOBEK Rural 1DFLOW model was set up to simulate the general hydrodynamics. This model included the two important spillways that are operated during high flow conditions. A weighted multi-criteria calibration procedure was performed to calibrate the model for high flows. Validation for floods in 2011 indicated a reasonable performance for high flows and clearly demonstrated the influence of the spillways. 32 different scenarios were defined which included the relatively large sea level rise and the changing discharge regime that is expected due to climate change. The impact of these scenarios on the water levels near New Orleans were analysed by the hydrodynamic model. Results showed that during high flows New Orleans will not be affected by varying discharge regimes, since the presence of the spillways ensures a constant discharge through the city. In contrary, sea level rise is expected to push water levels upwards. The effect of sea level rise will be noticeable even more than 470 km upstream. Climate change impacts necessitate a more frequent use of the spillways and opening strategies that are based on stages.
Highlights
The Mississippi River has the third largest river basin of the world and drains 41 % of the area of the United States
The flood risk of the Mississippi River imposed on urban areas, like Baton Rouge and New Orleans, became apparent during the great flood in 1927 which was the most destructive river flood in the history of the United States (Barry, 1998)
Climate change induced sea level rise in combination with the local subsidence of the Mississippi River Delta causes the projected local relative sea level rise in 50 yr to range between +0.5 m and +0.9 m for different rates of sea level rise (USACE, 2009; NOAA, 2011)
Summary
The Mississippi River has the third largest river basin of the world and drains 41 % of the area of the United States. Climate change induced sea level rise in combination with the local subsidence of the Mississippi River Delta causes the projected local relative sea level rise in 50 yr to range between +0.5 m and +0.9 m for different rates of sea level rise (USACE, 2009; NOAA, 2011). The uncertainty in these projections is large, since the local subsidence rates
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