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Castletroy Community CollegePhoto: David Hawgood · CC BY-SA 2.0
B+Hazard risk Grade
Flood & hazards in Castletroy · EPA, GSI and OPW data

Quiet on hazards: Castletroy has low radon, steady ground and few homes beside big water

With 1.8% of its homes standing low beside the River Shannon, Castletroy grades B+ for hazard risk: #3 of 15 in County Limerick; flood counts only against a town, and here it does.

1%of homes over the radon level
In brief

What stands out about Castletroy’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.

Few homes by big waterUnder 2% of homes stand low by a big river, lake or the sea. Small streams, drains and groundwater aren’t in that measure.Some radonAbout 1% of homes are estimated above the radon reference level, a lower share than in 83% of Irish towns; 0% of homes are in a High Radon Area.
By hazard

What Castletroy faces

Each hazard against its own yardstick; meters run from low to high on that yardstick.

Low-lying homes

1.8%of homes low by a big river, lake or the sea
a higher share than in 58% of Irish towns
About 88 homes

Radon

1%of homes estimated over the reference level
less radon than in 83% of Irish towns
0% of homes in a High Radon Area

Landslides

0.3%of homes on high or moderately high ground
more homes on it than in 80% of Irish towns
Rated from the ground and its slope

Ground heights

100%of homes on detailed ground heights
Enough to measure flood (80% needed)
Of 4,851 homes counted
Not on this page: the OPW’s official flood maps and past floods (their licence doesn’t allow reuse here: see floodinfo.ie), groundwater and surface-water flooding, coastal erosion and industrial sites.
Hazard risk Grade

Hazard risk in Castletroy: B+

Radon, landslide ground and low-lying homes, each against Irish towns, then averaged.

Radon (1%)Better than 76% of Irish towns
Landslide ground (0.3%)Better than 57% of Irish towns
Low-lying homes (1.8%)Better than 44% of Irish towns · counted against it

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 counts only against a town, and Castletroy’s share of low-lying homes is high enough to lower its grade.

Its place: #3 of 15 in County Limerick and #70 of 321 Irish towns.

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.

Low-lying homes

Few of Castletroy’s homes stand low by a big river, lake or the sea

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. Smaller streams, drains and groundwater aren’t in this measure, so a low figure doesn’t mean a town never floods.

By a river, lake or estuary1.8%of homes within 5 m of the water’s level
Near the sea0%of homes below 4 m, within 2 km of the sea
Measured in detail100%of homes on detailed ground heights
Where Castletroy sits among 231 Irish towns
43%None
6%Under 0.5%
4%0.5–1%
7%1–2%Castletroy
8%2–5%
6%5–10%
8%10–20%
18%20% +

Share of each town’s homes standing low by big water, for the towns measured in detail. 43% have none; Castletroy has more than 58% of them.

Towns its size: 27th of 40, from the fewest low-lying homes
#TownPeopleLow-lying
1Templeogue Dublin18,0760%
2Maynooth Kildare17,2590%
3Dundrum Dublin16,5700%
…
25Clonskeagh Dublin14,1420.2%
26Dún Laoghaire Dublin17,9940.3%
27Castletroy Limerick15,0931.8%
28Mallow Cork13,4561.8%
29Enniscorthy Wexford12,3101.9%
…
39Ballsbridge Dublin12,74355%
40East Wall Dublin15,907100%

The 40 Irish towns nearest its size that are measured in detail.

4,851
homes counted
88
homes standing low by big water
11%
County Limerick’s median
0.7%
median of Irish towns

Low-lying homes across County Limerick’s towns · 15 towns measured in detail

Corbally and King's Island48%
Ballinacurra39%
Newcastle West23%
Annacotty18%
Caherdavin15%
Dooradoyle15%
Limerick City Centre15%
Castletroy1.8%

Castletroy ranks 12th of County Limerick’s 15 towns measured in detail, counting from the most low-lying homes.

Homes: OpenStreetMap buildings of 30 m² or more, not tagged as non-residential, in the town’s Census 2022 Small Areas. Heights: GSI Open Topographic Data LiDAR (OPW, TII and GSI surveys). Water: EPA river network (rivers of Strahler order 5 or more), lakes, estuaries and coastal waters.

River levels

The River Mulkear at Annacotty peaked at 3.85 m in December 2015

Each winter’s highest level (October to September) at the OPW’s Annacotty gauge, 1.0 km from Castletroy on the same river, since 1972, in metres above the gauge’s zero. Nine days in ten it runs between 0.20 m and 1.53 m.

Each winter’s highest level, metres
Winter 1972–73: highest 3.21 m · 24 days above the normal rangeWinter 1973–74: highest 3.37 m · 49 days above the normal rangeWinter 1974–75: highest 3.36 m · 24 days above the normal rangeWinter 1977–78: highest 3.30 m · 27 days above the normal rangeWinter 1978–79: highest 3.03 m · 33 days above the normal rangeWinter 1981–82: highest 2.50 m · 34 days above the normal rangeWinter 1982–83: highest 3.43 m · 47 days above the normal rangeWinter 1983–84: highest 3.35 m · 40 days above the normal rangeWinter 1984–85: highest 2.61 m · 22 days above the normal rangeWinter 1985–86: highest 3.33 m · 31 days above the normal rangeWinter 1986–87: highest 2.90 m · 22 days above the normal rangeWinter 1987–88: highest 2.94 m · 42 days above the normal rangeWinter 1988–89: highest 3.21 m · 26 days above the normal rangeWinter 1989–90: highest 3.64 m on 6 February 1990 · 32 days above the normal rangeWinter 1990–91: highest 3.08 m · 40 days above the normal rangeWinter 1991–92: highest 3.19 m · 32 days above the normal rangeWinter 1992–93: highest 3.06 m · 34 days above the normal rangeWinter 1993–94: highest 3.24 m · 73 days above the normal rangeWinter 1994–95: highest 3.61 m on 22 February 1995 · 65 days above the normal rangeWinter 1995–96: highest 2.97 m · 24 days above the normal rangeWinter 1996–97: highest 3.33 m · 42 days above the normal rangeWinter 1997–98: highest 3.17 m · 42 days above the normal rangeWinter 1998–99: highest 3.22 m · 39 days above the normal rangeWinter 1999–00: highest 2.95 m · 41 days above the normal rangeWinter 2000–01: highest 3.33 m · 31 days above the normal rangeWinter 2001–02: highest 2.84 m · 34 days above the normal rangeWinter 2002–03: highest 2.62 m · 25 days above the normal rangeWinter 2003–04: highest 2.90 m · 12 days above the normal rangeWinter 2004–05: highest 3.17 m · 38 days above the normal rangeWinter 2005–06: highest 2.64 m · 18 days above the normal rangeWinter 2006–07: highest 2.95 m · 33 days above the normal rangeWinter 2007–08: highest 3.28 m · 55 days above the normal rangeWinter 2008–09: highest 3.23 m · 37 days above the normal rangeWinter 2009–10: highest 3.22 m · 49 days above the normal rangeWinter 2010–11: highest 3.05 m · 23 days above the normal rangeWinter 2011–12: highest 3.20 m · 45 days above the normal rangeWinter 2012–13: highest 3.27 m · 29 days above the normal rangeWinter 2013–14: highest 3.27 m · 62 days above the normal rangeWinter 2014–15: highest 3.39 m · 50 days above the normal rangeWinter 2015–16: highest 3.85 m on 12 December 2015 · 80 days above the normal rangeWinter 2016–17: highest 2.68 m · 27 days above the normal rangeWinter 2018–19: highest 3.52 m on 16 March 2019 · 32 days above the normal rangeWinter 2019–20: highest 3.79 m on 10 March 2020 · 65 days above the normal rangeWinter 2020–21: highest 2.62 m · 47 days above the normal rangeWinter 2021–22: highest 3.50 m on 20 February 2022 · 35 days above the normal rangeWinter 2022–23: highest 3.41 m · 61 days above the normal rangeWinter 2023–24: highest 3.11 m · 39 days above the normal rangeWinter 2024–25: highest 2.85 m · 22 days above the normal rangeWinter 2025–26: highest 3.25 m · 50 days above the normal range’15–16’19–20’89–90Record 3.85 m, 2015Top of normal range
1972–732025–26
The highest days on record
  • 12 December 20153.85 m
  • 10 March 20203.79 m
  • 6 February 19903.64 m
  • 22 February 19953.61 m
  • 27 December 19943.59 m
  • 16 March 20193.52 m

Since 1972 the River Mulkear has run above its usual top on 1,884 days, most of them in the winters of 2015–16 and 1993–94.

Measured by its highest day, last winter (2025–26) was the 20th-highest of the 49 on record here.

Source: OPW Hydro-Data (waterlevel.ie/hydro-data), Annacotty gauge (station 25001): daily maximum and mean levels, inspected and provisional data. The usual range is the 5th to 95th percentile of daily means, worked out by TownRatings. Live levels are on waterlevel.ie.

Warnings

Weather and flood warnings for Castletroy

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; Castletroy is covered by County Limerick’s.

WarningWhat Met Éireann means by it
YellowWeather that isn’t unusual but can be dangerous in places: be aware.
OrangeInfrequent, dangerous weather that can put people and property at risk: be prepared.
RedRare, 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 Castletroy can’t be counted here.

Met Éireann warnings · OPW river levels (waterlevel.ie)

Flood scheme

No OPW flood relief scheme protects Castletroy

The Office of Public Works’ completed flood relief schemes and the areas each one benefits (OPW open data, CC BY 4.0).

Schemes
0
protect homes in Castletroy
Protected places in the county
1
Annacotty
Nearest protected place
1.8 km
Annacotty, as the crow flies
Low-lying homes
1.8%
the share a scheme would be built for

None of the OPW’s completed flood relief schemes has a benefiting area that takes in Castletroy’s homes. The OPW builds schemes where the risk to homes is greatest, so most towns have none.

In County Limerick, an OPW scheme also protects part of Annacotty.

The protected places nearest here
TownSchemeDesigned forHomes behind itAway
Annacotty LimerickMulkear River (Ballymackeogh) Flood Relief Scheme1 in 101.1%1.8 km
Ennis ClareEnnis (Upper) Flood Relief Scheme1 in 1003.5%35 km
Gort GalwayGort River (Bridge Street) Drainage Scheme1 in 1000.9%48 km
Mallow CorkMallow South & West Flood Relief Scheme1 in 1002.6%59 km
Fermoy CorkFermoy South Flood Relief Scheme1 in 1006.3%61 km
Clonmel TipperaryClonmel (North & East) Flood Relief Scheme1 in 1007.4%67 km

Official flood maps and past floods: floodinfo.ie

Landslides

0.3% of Castletroy’s homes stand 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

CastletroyCounty Limerick’s medianmedian of Irish towns
High or moderately high0.3%
0%5%

That is a higher share than in 80% of Irish towns; the median is 0% for County Limerick’s towns and 0% for Irish towns.

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).

Radon

An estimated 1% of Castletroy’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.

21% of homes estimated above the reference level · Over 20% (High Radon Area)10% of homes estimated above the reference level · 10–20% (High Radon Area)1.6% of homes estimated above the reference level · 1–5% of homes0.1% of homes estimated above the reference level · Under 1% of homes0% of homes estimated above the reference level · Under 1% of homes1% of homes estimated above the reference level · 1–5% of homes1% of homes estimated above the reference level · Under 1% of homes1.4% of homes estimated above the reference level · 1–5% of homesunder 0.1% of homes estimated above the reference level · Under 1% of homes3.6% of homes estimated above the reference level · 1–5% of homes0% of homes estimated above the reference level · Under 1% of homes0.8% of homes estimated above the reference level · Under 1% of homes4.5% of homes estimated above the reference level · 1–5% of homes© OpenStreetMap contributors · EPA
Under 1% of homes1–5% of homes10–20% (High Radon Area)Over 20% (High Radon Area)
Share of Irish towns in each band
Under 1% of homes17%
1–5% of homes · Castletroy38%
5–10% of homes26%
10–20% (High Radon Area)11%
Over 20% (High Radon Area)9%

A square where 10% or more of homes are estimated above the reference level is a High Radon Area; 0% of Castletroy’s homes are in one. The map is an estimate by area: two neighbouring houses can differ a lot.

0%
of homes in a High Radon Area
1.6%
County Limerick’s median
4%
median of Irish towns

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).

Industrial sites

One EPA-licensed site lies inside Castletroy

Factories, farms, power plants and waste sites that hold an EPA licence for their emissions, in Castletroy and around its centre.

1
licensed site inside Castletroy
5
licensed sites within 5 km of the centre
1.5 km
to the nearest: Cook Ireland Ltd
The 8 nearest licensed sites
SiteLicence and activityAway
Cook Ireland LtdIPC licenceinside
Johnson & Johnson Vision Care Ireland Unlimited CompanyIndustrial Emissions licence · solvents and coatings1.8 km
Galvotech lreland LimitedIndustrial Emissions licence2.8 km
Info-Lab LimitedIPC licence3.8 km
Zinc Processors Limited Trading As Shannonside GalvanizingIndustrial Emissions licence · metals4.4 km
Longpavement landfill siteWaste licence5.5 km
James McMahon LimitedIPC licence6.4 km
J.H. Roche and Sons LimitedIndustrial Emissions licence · food and drink6.6 km
What the 18 licensed sites within 10 km do
ActivitySites
Not classed in the register7
Waste3
Chemicals3
Solvents and coatings2
Metals1
Food and drink1
Cement and lime1

Within 5 km: 3 under Industrial Emissions licences and 2 under older IPC licences.

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.

Neighbours

Hazards in the places around Castletroy

Low-lying homes, radon and landslide ground, town by town.

AnnacottyGarryowenWestburyGalvoneCorbally and King's IslandRathbaneAnnacottyGarryowenWestburyGalvoneCorbally and King's IslandRathbaneCastletroy
TownLow-lyingRadonLandslides
Castletroy1.8%1%0.3%
Annacotty
3,398 · 1.8 km		18%1%0%
Garryowen
5,428 · 2.8 km		1%1.5%0%
Westbury
3,636 · 3.5 km		91%1.6%0%
Galvone
5,412 · 3.6 km		0%1.6%0%
Corbally and King's Island
14,213 · 3.8 km		48%1.6%0%
Rathbane
4,111 · 4.1 km		3.8%1.4%0%

Of the places around Castletroy, Westbury has the most homes standing low by big water (91%), 3.5 km away.

A dash under Low-lying: not measured there (too few homes with detailed ground heights), not none.

Be ready

Get ready for what Castletroy faces

What to do, and what to ask before you move.

When the river rises
  • 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.
Met Éireann warnings · floodinfo.ie
Radon
  • 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.
radon.ie
When a storm is forecast
  • 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.
ESB Networks PowerCheck
Before you buy or rent in Castletroy
  • 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.
How to read these numbers

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 Castletroy

Does Castletroy flood?

Smaller streams, drains and groundwater aren’t in that measure, so it doesn’t mean the town never floods. For a single address, the OPW’s official flood maps and past floods are on floodinfo.ie.

Is radon a problem in Castletroy?

The EPA’s map estimates that about 1% of homes around Castletroy are above the radon reference level of 200 Bq/m³: a lower share than in 83% of Irish towns. 0% of its homes are in a High Radon Area. The only way to know a house is a three-month test.

Is Castletroy at risk of landslides?

0.3% of Castletroy’s homes stand on ground rated high or moderately high for landslides. Most slides happen on steep slopes and peat after heavy rain.

Is Castletroy at risk from the sea?

None of Castletroy’s homes stands below 4 m within 2 km of the sea, so the sea plays no part in its share of low-lying homes; 1.8% stand low by rivers, lakes and estuaries.

How does Castletroy compare with the places around it?

Radon estimates around Castletroy run from 1% in Annacotty to 1.6% in Westbury; Castletroy’s own is 1%. Among the places measured in detail, Westbury has the largest share of homes standing low (91%).

How is Castletroy’s Hazard risk Grade worked out?

Castletroy grades B+: 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 · river levels: OPW Hydro-Data (waterlevel.ie/hydro-data) · 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).