There are these things called alluvial fans. They occur when a river gets stumbling drunk and deposits/blows/ralphs its insides at the feet of its unrequited love--the delta. In this regard, the delta expects it. The delta exists for it. There aren't many things for which they exist mutually. You say they can't be what they've always been, but symbiosis is all they know. In this regard I'm wrong because alluvial fans occur when the river abruptly decreases in velocity, or even stops, causing silt and sediment to pile up in said love's mouth which is a ravine, you say, and not a delta. The difference gouges deep. For the sake of argument, I'm the river and you're the ravine, and I've been dammed, but this isn't funny to you.