JARVIS REC: Sulby Valley Crossing Points

TERRAIN ANALYSIS: The Sulby River valley is IoM's main natural corridor north-south. Every river crossing point (ford, bridge, stepping stones) is an archaeological hotspot. WHY: (1) The TT course follows this valley because it's the natural route — people have used it for 5,000+ years, (2) River crossings CONCENTRATE activity — everyone from Bronze Age farmers to Norse warriors to medieval merchants had to cross at the same points, (3) Rivers themselves carry washed-out items downstream — check gravel bars after floods, (4) The Cronk Sumark hillfort guards this valley. Strategy: identify every crossing point on OS maps, detect 50m upstream and downstream on both banks.