Buying a building plot in or around Alexandria? See how the ground falls and what constraints apply before you commit, using the Scottish Government LiDAR flown over the area and published on the Scottish Remote Sensing Portal.
Across the Alexandria area (4.04 km² from the OS Open Names extent), open LiDAR covers 99.8% of the ground. The best survey for most of it is LiDAR for Scotland Phase 3, flown 2015–2019 on a 0.5 m grid (96.7% of the area).
Other parts use LiDAR for Scotland Phase 1, flown 2011–2012 (1.9%); LiDAR for Scotland Phase 2 (DTM only), flown 2012–2014 (1.1%). A plot near the join between surveys may draw on both; the report shows which survey covers each part of your boundary.
That survey is about 7 years old. Plots in Alexandria that have been cleared, filled or built on since then won't show those changes, so the report flags the date at the top of every page and checks for buildings mapped since the flight where it can.
Most of the ground across the area (96% of readings) lies between 6.2 m and 96.5 m above Ordnance Datum, with a median of 21.4 m. The extremes (3.8 m to 113.2 m) can include water surfaces and data edges, so we don't quote them as ground levels.
That makes Alexandria steep ground by Scottish town standards: about a quarter or more of it falls faster than 1 in 10. On slopes like that, the cut-and-fill estimate and the fall across the plot are often the numbers that change a build budget most, so they're worth seeing before an offer.
Tiles from LiDAR for Scotland Phase 6 (flown 2022); LiDAR for Scotland Phase 5 (flown 2021) also overlap the Alexandria extent, but where surveys overlap the report uses the best one, as above.
Fitting a plane through the 10 m levels, the ground across Alexandria falls generally towards the east at about 46.6 m per km (roughly 1 in 21). The lowest tenth of the ground lies mostly to the south-east, and the highest tenth lies mostly to the south-west.
About 31.5% of the 10 m samples are flatter than 1 in 40, while one in ten is steeper than 10.9°.
On SEPA's flood maps (medium likelihood), 14.9% of the Alexandria extent is inside the river flood extent, 8.3% inside the surface water extent and 0.4% inside the coastal extent. The extent is a rectangle round the town, so it can take in foreshore, sea and open ground. These are indicative national maps, not a flood risk assessment; a plot report gives the figures for your own boundary.
Historic Environment Scotland has 37 listed building records in the extent (4 category A, 22 category B, 11 category C), and no scheduled monuments or conservation areas overlapping it. A plot report lists any that touch or sit near your boundary.
No NatureScot SSSI, SAC, SPA, Ramsar site or National Nature Reserve overlaps the Alexandria extent.
None of the Alexandria extent is within the Coal Authority's Development High Risk Area.
Nearest towns with pages here: Dumbarton, 4.8 km south, median ground about 13 m lower; Port Glasgow, 9 km south-west, median ground about 75 m higher; Helensburgh, 9.6 km west, median ground about 9 m higher; Erskine, 11.6 km south-east, median ground about 6 m lower.
Sampled every 10 m, the typical slope is 2.9°, and 32.2% of the area is steeper than 1 in 10. A single plot can be much flatter or steeper than this. Its report works at 0.5 m.
| Area checked | 4.04 km² (OS Open Names extent, at most 6 km across) |
|---|---|
| LiDAR coverage | 99.8% |
| Best survey | LiDAR for Scotland Phase 3, flown 2015–2019, 0.5 m grid (96.7%); typical ±0.14 m |
| Also used | LiDAR for Scotland Phase 1, flown 2011–2012, 1.000002600000007 m grid (1.9%); typical ±0.15 m |
| Also used | LiDAR for Scotland Phase 2 (DTM only), flown 2012–2014, 1.0 m grid (1.1%); typical ±0.15 m |
| Ground levels | mostly 6.2–96.5 m AOD (2nd–98th percentile), median 21.4 m |
| Slope (10 m sample) | median 2.9°, 90th percentile 10.9°, 32.2% steeper than 1 in 10 |
| Overall fall | towards the east, about 46.6 m per km |
| SEPA flood maps (medium likelihood) | river 14.9%, surface water 8.3%, coastal 0.4% of the extent (awareness only, not a flood risk assessment) |
| HES records in extent | 37 listed buildings (A 4, B 22, C 11), 0 scheduled monuments, 0 conservation areas, 0 gardens and designed landscapes |
| NatureScot protected areas | 0 |
| Coal Authority high risk area | 0.0% of the extent |
Read from the open LiDAR at a 10 m sample on 2026-10-23; local data checked 2026-10-23. A plot report reads the same data at 0.5 m for your boundary only.
Accuracy. We test Scottish LiDAR against independent survey overlaps and Ordnance Survey levelled trig pillars: heights are ±0.14 m typical on open ground (95% within ±0.28 m). Results by survey phase.
Dumbarton · Port Glasgow · Helensburgh · Erskine
Place names and extents: OS Open Names. Contains OS data © Crown copyright and database right 2026. LiDAR: contains Scottish Government LiDAR data, Open Government Licence v3. ©SEPA 2025; this SEPA product is licensed under the Open Government Licence version 3.0. Third-party data attribution statements: https://www.sepa.org.uk/media/5zidnja5/sepa_flood_maps_data_attribution_statements.pdf (SEPA flood maps are indicative and not suitable for individual properties). Contains Historic Environment Scotland and Ordnance Survey data © Historic Environment Scotland - Scottish Charity No. SC045925 © Crown copyright and database right 2026. Open Government Licence v3. Contains NatureScot information licensed under the Open Government Licence v3. Contains Mining Remediation Authority (formerly the Coal Authority) data, Open Government Licence v3. See data licences.