Answer: floodplain

AnswerCrossword Clue
FLOODPLAINRiverside, perhaps
FLOODPLAINBad place to live when the river rises
floodplainan area bordering a stream over which water spreads when the stream tops its channel banks
floodplainAn area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding