The tidal Thames, Teddington to the sea
Once it's in the river, it doesn't go straight out.
The Thames through London is tidal. A spill is carried up the river, then back down, twice a day, moving a little closer to the sea each time.
one
Back and forth, twice a day
Pick a tide, release a spill, and watch a week go by.
Day 0. Nothing released yet.
A sketch of the idea, not a forecast. The pale bar marks the stretch the spill has touched. The pace comes from a government study: about one month from Teddington to the sea in winter, three in summer.
two
More than half head upstream first
of spills into the tidal Thames in London began on a rising tide
They bunch up in the hours before high tide. Spills everywhere else in our records show no such pattern.
When spills into the tidal Thames began
Show the numbers
three
Then the tunnel opened
London's new super sewer was fully connected in February 2025. It catches overflows before they reach the river and carries them east to Beckton to be treated.
Spills into the tidal Thames
-- then --
The year before the tunnel, then the year after
Spills across the rest of London
-- then --
Same two years, no tunnel
Spills into the tidal Thames, month by month
The rest of London, for comparison
Show the numbers
four
Outfall by outfall
Every outfall in London that spilled straight into the tidal Thames, busiest first.
| Outfall | Spills | Began on a rising or falling tide | Before the tunnel | Since |
|---|---|---|---|---|
What we can't tell you
We know when each spill began, where, and what the tide was doing. We don't know how much came out, and we can't follow the water itself.
Tide times are worked out from tide data for the Thames estuary and checked against the Silvertown gauge. They match the gauge about 96% of the time.
Read the method →