Yes, flood risk is a real issue in Castle Green, though most of it comes from rain on the streets and only a little from the river. The river-and-sea zones cover only a small part of the area. The broader indicators flag most of its postcodes. Only a handful of individual homes are rated high risk from rivers and the sea. The district next door is called Creekmouth, and the name gives the game away.
On the Environment Agency's river-and-sea mapping, about 8% of Castle Green's postcodes are in Flood Zone 3, the highest-probability band. Under 1% are in Flood Zone 2, the medium-probability strip just outside it. Zone 2 is a separate band with no overlap, so the small figure here is a narrow strip and doesn't understate Zone 3.
Surface water is a different measure. The postcode indicators below include flooding from heavy rain that can't drain away fast enough, alongside rivers and the sea. The gap between the 8% in Flood Zone 3 and the much larger shares on those broader indicators is made up of the other measures, surface water among them. A street well away from any river can still be on that list, because surface water collects wherever the drains fall behind. The Environment Agency's long-term flood risk service lets you check surface water and river risk separately for an exact address, and it's worth doing for any house you're seriously considering.
Allowing for climate change, the Environment Agency's future flood zone covers about 35% of Castle Green. That is a modelled projection of how far the zone could reach, and nothing has flooded there yet.
On insurance, a postcode with a high rating on any measure gets asked more questions, and in some cases quoted a higher premium, than one with no rating at all. Insurers price by individual address, so two houses in the same terrace can be quoted differently.
At postcode level, about 73% of Castle Green's postcodes carry a high rating on at least one of several flood measures, about 71% a medium rating and about 82% a low rating. A postcode counts if any one of those measures flags it, so the shares overlap. That makes them a measure of how widespread the exposure is, and says nothing about how deep any flooding would be.
Counting homes gives a much smaller picture. The Environment Agency's rivers-and-sea mapping lists 1,646 properties across the 43 postcodes in the area that carry any risk at all. Of those, 4 are at high risk, 14 at medium risk, 734 at low risk and 409 at very low risk, and none of the high-risk properties is a home. Postcodes with no river or sea risk at all don't appear in that count.
On defences, about 6% of the area's postcodes fall inside the high-risk flood extent with no defence in the model, and about 0.2% fall inside it with a defence in place. A defence shown in the model is a wall or barrier the model assumes will hold. Defences can be overtopped or breached, so "defended" means something stands in the water's way, and it doesn't mean the house is safe.
The nearest tide gauge in the national record is at Dover, where sea level rose by about 2.2 millimetres a year between 1961 and 2010. That is the rate measured at Dover over those years, and it doesn't predict what happens next in east London.
The Environment Agency's historic flood records show no recorded flooding inside Castle Green. That counts in its favour, though a clean record only covers the floods that were recorded and doesn't prove water has never come through.
Flood risk is one of Castle Green's weakest points. The river risk to individual homes is small, but heavy rain affects a large share of its streets, and a buyer who doesn't check the specific address takes that on without knowing it.