Complex sentence: To help mitigate the effects of erosion, there are alternative routes at different times of the year, but moorland trails and upland streams lead down into Swaledale, and almost exactly at its halfway point, the Coast to Coast crosses the Pennine Way at Keld.
Split into simpler sentences: To help mitigate the effects of erosion, there are alternative routes at different times of the year. At almost exactly its halfway point, the Coast to Coast crosses the Pennine Way at Keld.