Geographic inconsistency in the T-Rex escape scene

In the famous scene, the T-Rex cuts the non-electrified fences and walks right across the broken fences. But a few minutes later we see Alan and Lex (Sam Neill and Ariana Richards) standing at the edge of the fences and looking down at a DEEP DROP to an area far below ground level. So the question is, if the area behind the fences is a deep pit-like area, how did the T-Rex climb out earlier?

You can see this scene at https://www.youtube.com/watch?v=Rc_i5TKdmhs . At 3:19, T-Rex walks right across the broken fences, and the area behind the fences is apparently at ground level, allowing the T-Rex to escape with ease. Yet at 8:17, we see the area behind the fences is actually far below ground level -- which would actually make sense, because a deep pit would keep tourists safe and make it tough for dinosaurs to escape..