New Southgate's flood risk comes down from the sky more than up from the river. Hardly any postcodes fall in the river flood zones. About a quarter score high on at least one measure once rain is counted. No flooding is on record in the area. The river map is the wrong place to look.
On the Environment Agency's river-and-sea flood zones, about 1% of New Southgate's postcodes fall in zone 2, the medium-probability band, and under 1% fall in zone 3, the high-probability band beyond it. The two bands don't overlap. Zone 2 is the extra fringe beyond zone 3, so the small zone 3 share is the core of the river risk, not a part of zone 2.
Surface water is a different matter. Pymmes Brook runs through Brunswick Park and Arnos Park along the Waterfall Walk, and it is the obvious thing for a buyer to worry about. The bigger risk is heavy rain on a suburb of flats, terraces and roads that has too little ground to soak it up. That risk is spread across the whole area, including streets nowhere near the brook.
The Environment Agency also models how the flood zones grow with a changing climate. On that model, about 3% of the area's postcodes fall inside the expanded zone. It is a projection of where the zone could reach, and it does not mean any particular house will flood.
Insurers price flood cover by the address, and they use surface-water risk as well as the river zones. A home that is clear of the river zone can still get a higher quote if the surface-water mapping marks its street. Before committing, look up the exact address on the Environment Agency's long-term flood risk service and check the surface-water result as well as the river result.
The postcode-level indicators combine several measures, rivers, the sea and surface water, and count a postcode as high if any one of them is high. On that combined basis, about 24% of the area's postcodes are high on at least one measure, about 19% medium and about 35% low. This is the measure that picks up the rain risk, which explains why it is much bigger than the river-zone shares above.
The Environment Agency's rivers-and-sea mapping also counts individual properties. It lists 26 postcodes in the area with some river or sea risk, covering 724 properties. Of those, 2 are at high risk, 27 at medium and 265 at low, and none of the high-risk properties are homes. The other postcodes in the area are left off the list because the river mapping gives them no risk at all.
Under 1% of the area's postcodes fall inside the high-risk river flood extent with defences left out of the model, and the share is the same with defences included. Putting the defences into the model leaves the high-risk extent no smaller. Anyone describing a home here as "defended" is describing what the model contains, and the model shows the same high-risk area either way.
The nearest tide gauge in the records is Portsmouth, which measured sea level rising by about 2 millimetres a year between 1962 and 2023. That is the rate recorded at that gauge over those years. A suburb whose nearest gauge is on the south coast has no sea-flooding problem worth losing sleep over.
There is no recorded history of flooding in the area. That is reassuring as far as it goes, but it only covers floods that were recorded, and surface-water flooding often affects a few gardens and a road without being logged.
New Southgate's flood risk is below average, mostly because of rain rather than the brook. A buyer who checks only the river zones will think the risk is lower than it is.