Fortune dealt a bad hand for the annual GEO2042 fieldtrip to the Ouseburn. For the first time in six years, it rained before and during our visit to collect water and invertebrate samples. By lunchtime, the water levels had gone up so much that we were worried that the afternoon’s session may have to be abandoned, for safety reasons. Fortunately, the rain eased at about 1300 and the river levels started to drop again.
Fieldwork on the Ouseburn, Jesmond Dene, October 2014. Left: kick sampling for invertebrates in the river; right: investigating the contents of a pond net.
The progress of the day’s storm are neatly demonstrated on the Environment Agency’s excellent realtime water level monitor, situated about a kilometre upstream from where we were working. The two groups of students were out between 1100 and 1200 and between 1300 to 1400 – either side of the highest level recorded at about midday. Look how quickly the water level rose from the baseline. This particular rainfall followed a long period of warm, dry weather, which has kept water levels down all over the region. The Ouseburn flows through built up areas of Newcastle for most of its short length, which means that a lot of the water will run straight off hard surfaces, into drains and into the river. Hence the rapid rise of the river levels, followed by the gradual drop as the water that had soaked into the ground gradually found its way to the river. Compare this brief storm event to the hydrograph for the River Coquet that I showed earlier in the year (see “Fieldwork in Northumberland”). In this instance, the river level went up more gradually, reflecting the much lower proportion of hard surfaces in the upstream catchment, before gradually declining. To the trained eye, these graphs show the effect of man’s alteration of rivers just as clearly as any measurement of “pollution”.
River Levels in the Ouseburn, 5th – 7th October 2014, from the Environment Agency’s monitoring station at Crag Hall, about a kilometre upstream from Jesmond Dene (http://apps.environment-agency.gov.uk/river-and-sea-levels/120691.aspx?stationId=8058)
One of the legacies of less-enlightened times that we have inherited is a system of combined sewers that carry both foul waste (don’t ask) and storm runoff. One effect of prolonged rainfall is to fill these sewers with water from drains and, for this reason, there are overflows built into the system which let the excess flow straight from the sewers to the rivers. Unfortunately, this overflow includes untreated sewage as well as storm runoff and, by Monday afternoon, the river had a distinctly unsavoury odour. The long-term plan is to replace these combined sewers with separate networks of storm drains and foul sewers. That, however, will take a long time, a lot of money (an awful lot of money) and, as most sewers run under our roads, serious disruption, to implement. So we will probably have to live with these combined sewer overflows for some time to come.
A hint for any GEO2042 students who have read this far: link the words “Ouseburn” and “combined sewer overflows” in your minds now. This might come in useful when you write up your project later this term. Enough said