Proverb meaning that even an expert can make a mistake; everyone slips up sometimes.
河童の川流れと言うから、今回のミスは仕方がないよ。
They say 'even a kappa can be swept away by the river,' so this mistake is unavoidable.
彼は料理の名人だけど、河童の川流れで焦がしてしまった。
He's a master cook, but even he slipped up and burned it.
スポーツでも河童の川流れはあるから、責めすぎないであげよう。
Even in sports, experts have lapses, so don't be too hard on them.