es , ▁leaving ▁an ▁area ▁of ▁salt works ▁near ▁the ▁heart ▁of ▁Ay am onte ▁which ▁de gr ades ▁the ▁mar sh ' s ▁landscape . ▁This ▁unit ▁forms ▁a ▁ 2 3 7 ▁hect ares ▁island ▁of ▁al ma jos ▁and ▁Fran ken ia ceae ▁pra i ries . ▁In ▁its ▁southern ▁area ▁the ▁de grad ation ▁from ▁urban isation ▁is ▁quite ▁high . ▁ ▁Sal ón ▁de ▁Santa ▁G ade a ▁▁ ▁Connect s ▁directly ▁with ▁Ay am onte ▁and ▁more ▁than ▁half ▁of ▁its ▁ 9 7 ▁hect ares ▁are ▁sal ty . ▁Al ma jos ▁and ▁need le gr ass ▁are ▁the ▁most ▁abund ant ▁veget ation . ▁ ▁Geography ▁▁ ▁The ▁current ▁hydro graph y ▁goes ▁back ▁to ▁the ▁ 1 7 5 5 ▁Lis bon ▁earth qu ake ▁and ▁the ▁success ive ▁accum ulation ▁and ▁removal ▁of ▁sed iments , ▁as ▁well ▁as ▁being ▁influenced ▁by ▁the ▁Gu ad iana ▁and ▁recently ▁the ▁T into - O d iel ▁rivers ▁because ▁of ▁the ▁construction ▁of ▁the ▁Juan ▁Carlos ▁I ▁break water ▁and ▁other ▁d ikes ▁that ▁modify ▁the ▁flow ▁of ▁sed iments . ▁For ▁a ▁structure ▁by ▁zones , ▁see ▁the ▁structure ▁of ▁the ▁mar sh es . ▁ ▁They ▁frame ▁the ▁Car rer as ▁river ▁est u ary , ▁greatly ▁influen cing ▁it ▁with ▁the ▁dy kes ▁on ▁the ▁west ▁and ▁east ▁of ▁Is la ▁Crist ina ▁port ▁town ▁and ▁largely ▁limit ing ▁the ▁accum ulation ▁of ▁depos its ▁and ▁the ▁decrease ▁of ▁river ▁branch ing