I live near a 300 acre industrial estate which has taken over 1 year to be built so far. It's VERY obvious that site is emitting soil particles all the time. Yet your graph only shows "Cultivation". This is not correct and is biased. I don't see any evidence of sewerage outfalls. I know my drainage ditches have deposits mainly from rabbits and badgers which deposit subsoil into ditches in large quantities. I also know in my village large amounts of water from A roads erode banks and flood fields.