People often say: "Thirty years east of the river, thirty years west of the river." Please explain this sentence with your geographical knowledge and tell me what your inspiration is.

Rivers have two effects on the formation of landforms: erosion and accumulation. For relatively straight rivers, considering the influence of geostrophic deflection on horizontally moving objects, the right bank of rivers in the northern hemisphere erodes the left bank, while the left bank of rivers in the southern hemisphere erodes the right bank. For the curved river, the concave bank of the river is eroded and the convex bank is accumulated due to the bend effect.

"A few new homes, the great rivers of the past. The ancient shore is about to collapse, and the flat sand is not stopped. "Thirty years east of the river and thirty years west of the river" are all shaping the landform by the above rivers.