city concrete cool cooling falling water feature flow flowing fountain fresh froth graining gray grey movement moving peace peaceful plants pool reflection reflections rippling rough spray streaming textures wall water water fall white Athabasca boulder canada current deluge drop falls fierce landscape natural nature plunge pour river rock Rockies Rocky Mountains torrent turmoil waterfall England english Fluvial landforms of streams forest Great Britain green Horsebridge Natural landscape plant sky Tamar trees Banff bank Bow Falls channel conifers danger dangerous foam rage rapids rocks violent boulders countryside exercise footpath hike hillside mountain norway norwegian path snow track trail walk wild Arun field hill meadow placid rural summer Sussex chalk cliff banks Bedfordshire bridge course great Ouse oxygenate oxygenation waterweed weir