This noun can also describe other kinds of "going back," like the recession of floodwaters that enable people to begin cleaning up their homes that had been filled with water.

【翻译】这个名词还可以描述其他类型的“衰退；撤退；衰微”，就像洪水的衰退一样，使人们能够开始清理已经被洪水注满过的房子。

本句在描述一个“名词”的用法，整个段落采用一般现在时。但定语从句则使用了过去完成时。正如网友所言，似乎缺少一个参照物（一般过去时）。其实，这个一般过去时的动作被省略掉了，我们可以补足这个参照物（见：红色部分，说明水灾在过去发生）：... their homes that had been filled with water before the floodwater went back.

我查了一下这个句子的出处，网友提供的句子不错：

https://www.vocabulary.com/dictionary/recession

这是国外网站上的原文，该网站是很权威的英语词汇研究网站。

Recession comes from the Latin word recessus, meaning "a going back, retreat." Think of all the things that get made and sold in a country. When fewer people buy things, orders for them slow down. The sales "go back" to a lower amount. This is an economic recession. This noun can also describe other kinds of "going back," like the recession of floodwaters that enable people to begin cleaning up their homes that had been filled with water.

定语从句的先行词可否是 other kinds of "going back"？这样的话，enable 就讲得通了。