主题：房屋保护题型：流程图Thediagramsbelowshowhowhousescanbeprotectedinareaswhicharepronetoflooding.满分范文：Thediagramscomparetwodifferentmethodsofdefenceforhomeswhichareatriskofbeingflooded.Thekeydifferencebetweenthediagramsisthattheyshowfloodprotectionwithandwithoutastopbank.Ineithercase,theat-riskhomeisraisedonstiltsabovegroundlevel.Thefirstdiagramshowshowastopbankactsasafloodbarriertostopriverwaterfromfloodinghomes.Thestopbankisasmallmoundoflandnexttotheriverthatishigherthanthe100-yearfloodlevel,andpreventstheriverfromburstingitsbanks.Nearbyhousescanbebuiltonstiltstopreventfloodingfromrainwater,andafloodgatebeneaththestopbankcanbeopenedtoallowthis‘ponding’todrainoffintotheriver.Whenthereisnostopbank,asshownintheseconddiagram,therewillbenothingtostoptheriverfromflooding.Inthiscase,thesolutionistoputbuildingsonstilts.Theheightofthestiltsismeasuredsothatthefloorofthehouseis300mmabovethe100-yearfloodlevel.Thismeasurementiscalledthe‘freeboard’.
