one difficulty that had to be overcome in respect of the descending torrent of water was just where the downpour would fall to earth : it is all perfectly fine for more than 100,000 cubic feet per second of water to carry itself over niagara falls when it has the expansive basin of the niagara river to empty itself into , and fine for the carrao river to drop almost a mile vertically over angel falls when it is surrounded by dense rain forest and has the myriad tributaries of the gran sabana to disperse into , but a city centre waterfall of grand dimensions had the potential for being a nuisance .