river river short river miles length rises england upper reaches underground urban landscapes emerges open flows nature reserve city parks joining tidal river sea mills 18th century water mills near mouth gave area roman port mouth provided point journeys 18th century short lived attempts creating port whale fishery appears anglo saxon roots recent years problems caused urban development caused difficulties works helped reduce problem course rises near area upper course underneath 20th century housing surfaces bristol suburb flows open nature reserve south quarry fed springs overflow running river village divert water storm drain times high rainfall save village centre flooding disappears emerging entering estate joined right bank remains fed seen passing road bridge river flows river park passing railway line joining river prevents flooding upstream highest spring tides natural history nature reserve managed areas beech oak ash woodland support range bushes shrubs including maple housing estate native meadow plants including yellow wild wildlife includes native woodland birds including bats estate contains variety trees plant life providing cover birds small mammals downstream invasive riverside plants established ducks found stretches river estuary birds near mouth pollution incident allowed sewage flow killing invertebrates resulted fine following prosecution pollution incidents followed history confluence roman port small town took main river simply means river staging point roman invasion wales western end roman road 15th century tide mills near mouth attempt entrepreneur open commercial dock mouth roman site venture decades whale fishery enterprise set equally short lived parts dock walls seen etymology sources indicate derive anglo saxon meaning firm strong flow river decreased power recent years partly surface run upper especially large retail centre causeway sends good deal system slowing flow creating risk flooding downstream problem partially construction reservoir near causeway measurements pollution city council water relatively clean
River Trym