In the studies about natural hazards it is very important to use an adequate cartography about the variables studied to determine with high precision the potentially affected areas.
The main problem in making cartographies about sea levels along the coast is the high variability of the mean sea level. In some parts of Spain, the mean sea level does not match with the one of Alicante (NMA), which is the zero value for Spanish topographic maps. Because of this, cartographies of sea levels are only correct in areas where the topographic zero has the same value as the local mean sea level. Moreover, the scarce number of tidal gauges makes it difficult to make precise corrections along the coast.
The aim of this work is the development of a simple methodology for minimizing the errors due to the interpolation of mean sea levels from the data of tide gauges. We have used the data of extreme sea levels with a return period of 200 years. The studied area is the fluvial marshes of Doñana National Park, a zone especially exposed to a sea level rise, where the application of this methodology shows very different results to the ones that would have been obtained by not considering the differences between the NMA and the local mean sea level.