Our environmental report came back as high risk for surface water flooding only. We aren’t near any rivers, streams, sea etc.
It’s a 4 year old estate of 16 houses. Only a terrace of 3 houses are detailed as high risk on the govmt flood data. The other 13 are all low risk. Subsequently, we’ve had a more detailed report done. It has identified the area as a whole as having a 1 in 75 year chance of moderate SW flooding due to it being built down on the grounds of an old railway station. So the estate is on slope. The new report advises they haven’t taken into account any SUDs systems installed & we’ve got confirmation from the council & building company there are a couple on the estate. We’ve even been sent photos.
Anyway, the new report talks about the elevation of the estate & the fact our house is on a higher elevation than the majority of the other houses. Which is correct. We are near the top of the hill. The estate carries on downwards past us. The new report actually marks the bottom of the estate as the bit at risk of this moderate flooding & not the 3 houses marked on the original environmental report at all. 
How can they be so different? How can one set of data think only our house (& the attached terrace) are at risk and another set of data think actually, not us at all but elsewhere 😫 It has all set our minds at ease in many ways but it’s very confusing. Any flood experts cast their opinion as to why this difference?
Thanks!