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174D. MUEHEFigure 1. Evolution of the average surface temperature projected by the IPCC in 2007.Nobre et al. (2007) produced climateprojections for the next 30 years of the century inSouth America for various emission scenarios. Interms of precipitation these predictions showdiscrepancies in the forecasted anomalies in terms ofeither increase or decrease. Although the discrepanciesbetween the results are small they will affectnegatively or positively areas that are alreadyexperiencing water deficit as in the NortheastRegion of Brazil, where the projections for thecoastal zone indicate anomalies varying from verysmall to an increase and even decrease in the amountof precipitation. However, even with no significativechange in rainfall, the augmented evaporationcaused by the temperature increase will result inaugmented water shortages in the semi-arid regions.The temperature forecasts by Nobre et al.(2007) for the coastal zone are similar to thescenario forecasted by the IPCC (2007) and indicatea temperature increase in the range of 2 ºC to 3 ºC.The perception of risk from sea level risewas incorporated into the ORLA Project of theMinistry of Environment (Ministério do MeioAmbiente 2004) through the establishment of setbacklines of 50 m in urban areas and 200 m in ruralareas. This distance would be measured landwardeither from the backshore limit or from the dune toeof the reverse side of foredunes when present. Theestablishment of the width of these set-back linesresulted from a conciliation between the results ofthe application of the Bruun rule (Bruun 1962,1988), for an increase of an 1 m sea level rise(Muehe 2001, 2004), and the impossibility of itspractical application in areas of very low gradient ofthe shoreface and inner shelf as in the north andnortheast regions where the results of the modelindicate very large recession of the coastline (Fig.2).The adopted limits represent a firstminimum restriction to be considered in theurbanization of coastal areas, and can be expandedaccording to local geomorphic characteristics suchas the known erosion rate and landscapeconservation.Coastlineretreat(m)1000010001001013 o 2 o 1 o 0.6 o 0.2 o 0.06 oSteepgradientIntermediategradientLowgradient NNESSSESENEd l,1 00d l,110 100 1000 10000Shorefacegradient (1:X)Figure 2. Coastline retreat in response to an elevation of1 m of relative sea level and a closure depth of the beachprofile of 5 m (dl, 1) and 10 m (dl, 100)), (Muehe 2001).NPan-American Journal of Aquatic Sciences (2010) 5(2): 173-183