( ( When ( forests ( are ( cut down ) ) ) ) ( , ( ( ( this regulation ) ( of ( ( the flow ) ( of water ) ) ) ) ( ( is ( ( disrupted , ) ( which ( leads ( to ( alternating ( ( ( periods ( of flood ) ) and ) ( ( then drought ) ( in ( the ( affected area ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNS forests)) (VP (VBP are) (VP (VBN cut) (PRT (RP down)))))) (, ,) (NP (NP (DT this) (NN regulation)) (PP (IN of) (NP (NP (DT the) (NN flow)) (PP (IN of) (NP (NN water)))))) (VP (VBZ is) (VP (VBN disrupted) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ leads) (PP (TO to) (S (VP (VBG alternating) (NP (NP (NP (NNS periods)) (PP (IN of) (NP (NN flood)))) (CC and) (NP (NP (RB then) (NN drought)) (PP (IN in) (NP (DT the) (JJ affected) (NN area))))))))))))) (. .)))
When forests are cut down, this regulation of the flow of water is disrupted, which leads to alternating periods of flood and then drought in the affected area.
(ROOT (S (SBAR (IN Because) (S (NP (NNS trees)) (VP (VBP add) (NP (NN water) (NN vapor)) (PP (TO to) (NP (NN air)))))) (, ,) (S (VP (VBG cutting) (PRT (RP down)) (NP (NNS forests)))) (VP (VBZ leads) (PP (TO to) (NP (NP (JJR longer) (NNS periods)) (PP (IN of) (NP (NN drought)))))) (. .)))