NewspapersoftentellusoffloodsinsomepartsoftheUnitedStates.
Nearlyeveryyearonthegreatcentraldrainagesheavyrainsandmeltingsnowcausethewaterstopouroutthemountainsandplains,toturnbrooksintotorrents,andtoswellquietstreamsintowilduncontrolledrivers.FromCairotoNewOrleans,andfromPittsburghtoPaducah,thecry"Riverrising!"isafamiliaryetfearfulvoice...Whentheriverssometimesbecometoohighortooswifttobecontrolledcommunitiesareflooded,familiesfleefromtheirhomes,croplandsarewashedout,andtransportationcomestoahalt.Hunger,disease,anddeathfollowthewildwaters.
Althoughgivenlesspublicity,theagriculturaldamagedonebythemanysmaller,morefrequentfloodsusuallyfarexceedsthelossescausedbytheverygrandones.IntheCentralStates,ditchesanddrainscausetheflowsfromspringrainsandmeltingsnowtorunfarmorerapidlythaninthedaysbeforewhitemensettledontheland.Once,excessspringfloodwatersemptiedintolakesandswampylands,theretobedetainedforslowreleaseintostreamandrivers.Now,systematicdrainagehasactuallyeliminatedthesenaturalreservoirs.
InthemorerollingsectionsoftheEast,springrunoffwasformerlyabsorbedandheldtemporarilyintheporoussoilsbeneaththeunbrokenexpanseofforest.Whenlargeareaswereconvertedtofarmuse,removaloftheforestandthepracticeofup-and-downhillplowingdeprivedthesoilsofmuchoftheirabilitytocatchandstorewater.
Theeffectsofeliminatingthenaturalforestcoverareshowninthegulliedfarmlandsandwidenedstreamchannelsfoundinsomedenselysettledareas.Partlybecausethestreamchannelsaremoreorlessfilledwithmaterialwasheddownfromtheuplands,andpartlybecausestormrunoffhasincreased,thechannelsaretodaynolongerabletocarryalltheflowfromheavyrains.Thisexplainswhythestreamsovertopbanksfarmoreoftenthaninthedaysbeforesettlement.
26.Thebesttitlefortheselectionwouldbe______.
A.RiverRising!RiverRising!B.ForestsandFloods
C.FloodingintheU.S.D.TheResultsofFlooding
27.AllofthefollowingcausefloodsEXCEPT______.
C.increasingstormrunoffD.poroussoil
28.Theauthorstatesthat______.
A.lakesandswampsonceactedlikenaturalreservoirs
B.up-and-downhillplowingcatchesandstoreswater
C.streamchannelsarethebestcarriersofwater
D.floodsareeasilypreventedandcontrolled
29.Accordingtotheselection,streamsovertoptheirbankspartlybecause______.
A.materialfromhigherlandiswashedintothem
B.ditchesanddrainsleadintothem
D.snowmeltsmorerapidlynowadays
30.Thefloodswhicharegivenmostpublicity______.
C.causelessagriculturaldamagethanthemanysmaller,morefrequentfloods
D.farexceedthesmaller,morefrequentfloodsinagriculturalloss
U245265618
U882667602
