在英语中，描述“河边行走时被冲走”这一场景，我们可以使用以下几种表达方式：
1. Being Swept Away While Walking in the River
这种表达方式直接而简洁，将动作和情境结合在一起，形成了一个完整的句子。
例句：
- I was being swept away while walking in the river, but my friends managed to pull me back to safety.
2. Walking Along the Riverbank and Getting Washed Away
这种表达方式将动作分解为两个部分，先描述行走，再描述被冲走的过程。
例句：
- Walking along the riverbank, I didn’t realize how strong the current was until I got washed away.
3. Being Pulled Off My Feet by the River Current
这种表达方式更加强调了水流的力量，将重点放在了被水流冲走的瞬间。
例句：
- The river current was so strong that it pulled me off my feet, and I was being swept away.
4. Getting swept off my feet while crossing the river
这种表达方式中的“get swept off one’s feet”是一个成语，通常用来形容某人因为爱情或兴奋而失去平衡。
例句：
- It was such a beautiful day by the river that I got swept off my feet while crossing it, almost losing my balance.
5. Being Drifted Away by the River’s Current
这种表达方式使用了“drift away”，给人一种被水流慢慢带走的感觉。
例句：
- Without realizing it, I was drifted away by the river’s current, and I had to swim back to the shore.
总结
在英语中，描述“河边行走时被冲走”的场景，可以根据具体情境和语境选择不同的表达方式。以上几种表达都能够在不同程度上传达出这一事件的发生过程。