Complex sentence: The Somerset Levels are divided in two by the Polden Hills; the catchment areas of the River Parrett are to the south, and the rivers Axe and Brue are to the north, where the Mendip Hills separate the Somerset Levels from the North Somerset Levels.
Split into simpler sentences: The Somerset Levels are bisected by the Polden Hills; the areas to the south are drained by the River Parrett, and the areas to the North by the rivers Axe and Brue. The Mendip Hills separate the Somerset Levels from the North Somerset Levels.