Photo: Jo Turner · CC BY-SA 2.0Radon is the hazard to test for in Knock: an estimated 11% of homes are above the reference level
For hazard risk, Knock grades C. It counts radon and landslide ground only; flooding isn’t measured here, so it isn’t counted either way.
What stands out about Knock’s hazards
From the EPA’s radon map, Geological Survey Ireland’s landslide map, the OPW’s flood relief schemes and our estimate of low-lying homes, below.
What Knock faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Low-lying homes
Radon
Landslides
Ground heights
Knock grades C for hazard risk
Radon, landslide ground and low-lying homes, each against Irish towns, then averaged.
Each figure is placed among Irish towns of 1,000 or more people; the grade averages the three, so a better place on each is a better grade.
Flood isn’t counted for or against Knock: too few of its homes have the detailed ground heights the measure needs, so its grade uses radon and landslide ground only.
Less sure: The low-lying figure is our estimate from ground heights and the river map, not an official flood map. It can show a town is low-lying; it can’t show a town is safe. No LiDAR here: the heights come from a 30 m satellite model, which reads roofs and trees as ground, so this town’s figure isn’t counted.
How many of Knock’s homes stand low isn’t measured
Low-lying homes, a TownRatings estimate from OPW and Geological Survey Ireland LiDAR ground heights and the EPA’s river map: not an official flood map.
Flooding isn’t measured in Knock: no LiDAR survey covers its homes, and the measure needs 80% of them, so flood isn’t counted for or against it. That doesn’t mean it doesn’t flood.
A rougher estimate, mostly from a 30 m satellite model, finds few homes standing low by big water, but that model reads roofs and trees as ground, so it can’t show the town is dry.
Weather and flood warnings for Knock
Where to see the warnings in force, and what this page can’t count.
Met Éireann issues yellow, orange and red warnings for rain, wind and coastal flooding county by county; Knock is covered by County Mayo’s.
| Warning | What Met Éireann means by it |
|---|---|
| Yellow | Weather that isn’t unusual but can be dangerous in places: be aware. |
| Orange | Infrequent, dangerous weather that can put people and property at risk: be prepared. |
| Red | Rare, extremely dangerous weather: take action to protect yourself and your property. |
Met Éireann doesn’t publish an open archive of past warnings, so how often warnings have covered Knock can’t be counted here.
No OPW flood relief scheme protects Knock
The Office of Public Works’ completed flood relief schemes and the areas each one benefits (OPW open data, CC BY 4.0).
None of the OPW’s completed flood relief schemes has a benefiting area that takes in Knock’s homes. The OPW builds schemes where the risk to homes is greatest, so most towns have none.
No other place across County Mayo has an OPW flood relief scheme either.
| Town | Scheme | Designed for | Homes behind it | Away |
|---|---|---|---|---|
| Baile Chláir Galway | Clare River (Claregalway) Flood Relief Scheme | 1 in 100 | 7.9% | 51 km |
| Ballinasloe Galway | Ballinasloe (Derrymullen) Flood Relief Scheme | 1 in 100 | 3.2% | 69 km |
| Gort Galway | Gort River (Bridge Street) Drainage Scheme | 1 in 100 | 0.9% | 82 km |
| Ennis Clare | Ennis (Upper) Flood Relief Scheme | 1 in 100 | 3.5% | 106 km |
| Mullingar Westmeath | Mullingar Flood Relief Scheme | 1 in 100 | 0.2% | 108 km |
| Tullamore Offaly | Tullamore Flood Relief Scheme | 1 in 100 | 2.4% | 111 km |
No home in Knock stands on landslide-prone ground
Geological Survey Ireland’s landslide susceptibility map (1:50,000), read at every home.
Homes on ground rated high or moderately high
Knock is among the 64% of Irish towns with no home on such ground.
GSI rates ground from low to high by its slope, soil and rock. Most Irish landslides are on steep upland slopes and peat after heavy rain; a town on flat ground has almost none.
High means the ground could slide under the right conditions, such as days of heavy rain on a steep, wet slope; it isn’t a forecast that it will.
GSI landslide susceptibility, high and moderately high classes, share of the town’s homes on mapped ground (CC BY 4.0).
An estimated 11% of Knock’s homes are above the radon reference level
The EPA’s radon map: for each 10 km square, the estimated share of homes above the national reference level of 200 Bq/m³.
A square where 10% or more of homes are estimated above the reference level is a High Radon Area; 9.4% of Knock’s homes are in one. The map is an estimate by area: two neighbouring houses can differ a lot.
A test is the only way to know a home’s level: two detectors, left for three months in a living room and a bedroom.
EPA radon map of Ireland (10 km grid), averaged over the town’s homes (CC BY 4.0).
No EPA-licensed site within 5 km of Knock: the nearest is 5.1 km away
Factories, farms, power plants and waste sites that hold an EPA licence for their emissions, in Knock and around its centre.
| Site | Licence and activity | Away |
|---|---|---|
| Martin and Mhairi Dempsey | Industrial Emissions licence · intensive farming | 5.1 km |
| Mr Eugene Lannon (Bernies Farm) | Industrial Emissions licence · intensive farming | 5.5 km |
| Mr Eugene Lannon (Hunts Farm) | Industrial Emissions licence · intensive farming | 6.1 km |
| Western Brand Group Unlimited Company | Industrial Emissions licence · food and drink | 7.0 km |
| Activity | Sites |
|---|---|
| Intensive farming | 3 |
| Food and drink | 1 |
An EPA licence sets what a site may release to air, water and land; it doesn’t mark the site as an accident hazard.
Sites holding dangerous substances in bulk come under the COMAH (Seveso) rules, but the HSA’s list of them has no open licence, so upper- and lower-tier sites aren’t counted here.
Source: EPA registers of Industrial Emissions, IPC and waste licences, sites licensed on 31 October 2026; distances in a straight line from the town’s centre.
Hazards in the places around Knock
Low-lying homes, radon and landslide ground, town by town.
| Town | Low-lying | Radon | Landslides |
|---|---|---|---|
| Knock | – | 11% | 0% |
| Kiltimagh 1,232 · 8.0 km | – | 11% | 0% |
| Claremorris 3,857 · 9.5 km | – | 14% | 0% |
| Ballyhaunis 2,773 · 10 km | 0% | 22% | 0.6% |
| Swinford 1,459 · 17 km | 0% | 21% | 0% |
None of the measured places around Knock has many homes standing low by big water.
A dash under Low-lying: not measured there (too few homes with detailed ground heights), not none.
Get ready for what Knock faces
What to do, and what to ask before you move.
- Never walk or drive through floodwater: 30 cm of moving water can float a car.
- Move valuables, papers and medicines upstairs.
- Turn off gas, electricity and water if you’re told to.
- Test over three months, in a living room and a bedroom.
- Above 200 Bq/m³, a small sump and fan usually fixes it.
- The EPA sells radon test kits at radon.ie and lists registered contractors who fix high readings.
- Bring in or tie down bins, trampolines and anything the wind can lift.
- Keep away from coastal paths and piers while an orange or red warning is in force.
- Charge phones and keep a torch: fallen lines are the commonest storm damage.
- After the storm, report a fallen line to ESB Networks and keep well clear of it.
- Ask whether the home has ever flooded, and get a buildings insurance quote before you commit: flood cover isn’t always offered.
- Ask the seller or landlord for a radon test result, or test in your first months there.
- Check the address on floodinfo.ie: the OPW’s flood maps and its record of past floods.
What this data can and can’t tell you
- An estimate, not a flood map. Low-lying homes is a TownRatings modelling step: each home’s ground height from LiDAR, against the level of the nearest big river (Strahler order 5 or more), lake or estuary within 1 km, or the sea within 2 km. A home within 5 m of the water’s level, or below 4 m near the sea, counts.
- Flood counts only one way. A high share of low-lying homes lowers the Hazard risk Grade; a low share never raises it, because defences, small streams, culverts, groundwater and flash floods don’t show in ground heights. Below the national median a town scores as the median.
- Defences aren’t counted. Flood defences aren’t taken off: the OPW scheme that protects the most homes is shown instead, with its design standard.
- Measured where the heights are detailed. A town is measured, and counted, only where 80% of its homes stand on LiDAR heights. Elsewhere the page says flooding isn’t measured, never that the town is dry.
- Radon is an estimate by area. The EPA’s radon map gives the estimated share of homes above 200 Bq/m³ for each 10 km square, averaged here over the town’s homes. It says where to test, not what one house holds.
- The sea is measured by height. Homes count as low by the sea when their ground is under 4 m and within 2 km of coastal or estuary water; waves, surges and erosion aren’t modelled.
- Landslide ground is a map of where slides could start. GSI’s susceptibility map rates the ground itself; it doesn’t record past slides or say when one will happen.
- Bathing water is rated season by season. The EPA classes each identified bathing water from four seasons of samples; a rating says how clean the water has been, not how safe it is to swim.
- One town, many streets. Risk is street by street. Check a specific address on floodinfo.ie before you buy or rent.
Check any address against the OPW’s official flood maps on floodinfo.ie
Questions about flooding and hazards in Knock
Does Knock flood?
For a single address, the OPW’s official flood maps and past floods are on floodinfo.ie.
Is radon a problem in Knock?
The EPA’s map estimates that about 11% of homes around Knock are above the radon reference level of 200 Bq/m³: a higher share than in 83% of Irish towns. 9.4% of its homes are in a High Radon Area. The only way to know a house is a three-month test.
Is Knock at risk of landslides?
No home in Knock stands on ground rated high or moderately high for landslides.
How does Knock compare with the places around it?
Radon estimates around Knock run from 11% in Kiltimagh to 22% in Ballyhaunis; Knock’s own is 11%.
How is Knock’s Hazard risk Grade worked out?
Knock grades C: radon, landslide ground and low-lying homes are each placed among Irish towns, and the grade averages them.
Flood: TownRatings’ estimate from ground heights, not an official flood map. Contains Irish Public Sector Data (Geological Survey Ireland, the Office of Public Works and the EPA) licensed under CC BY 4.0; Copernicus DEM © DLR e.V. and © Airbus, provided under COPERNICUS by the EU and ESA; © OpenStreetMap contributors. Radon and bathing water: EPA (CC BY 4.0). Landslide susceptibility: Geological Survey Ireland (CC BY 4.0).
Sources: low-lying homes: TownRatings’ estimate from GSI and OPW LiDAR, Copernicus GLO-30 and the EPA river network · radon: EPA radon map · landslides: GSI landslide susceptibility · industrial sites: EPA licence registers · the grade: TownRatings, from these figures. Under Creative Commons Attribution 4.0 (CC BY 4.0).
Contains Central Statistics Office (CSO) data, Census 2022, and Tailte Éireann boundaries (CSO Urban Areas, Small Areas, local electoral areas, constituencies), under Creative Commons Attribution 4.0 (CC BY 4.0).