Flood-risk data sources in Poland: ISOK maps, Wody Polskie, IMGW and LiDAR

Who produces flood-risk data in Poland

Polish flood-risk data is produced by three public institutions. Państwowe Gospodarstwo Wodne Wody Polskie, the state water-management holding, prepares the flood hazard maps (mapy zagrożenia powodziowego, MZP) and flood risk maps (mapy ryzyka powodziowego, MRP) in agreement with the voivodes, while the directors of the maritime offices prepare the scenarios for flooding from the sea. The Instytut Meteorologii i Gospodarki Wodnej (IMGW-PIB) operates the gauging and meteorological network, issues hydrological warnings and publishes its observations through an open data portal. The Główny Urząd Geodezji i Kartografii (GUGiK) keeps the national terrain model and the LiDAR point clouds that every hydraulic model is built on.

The maps are published through the Informatyczny System Osłony Kraju (ISOK), a system built under project POIG.07.01.00-00-025/09 with co-financing from the Innovative Economy Operational Program 2007 to 2013, designed and implemented by GISPartner and operated by the Krajowy Zarząd Gospodarki Wodnej (KZGW), the national water-management board that now sits inside Wody Polskie. Its public face is the Hydroportal, which serves the preliminary flood risk assessment, the hazard and risk maps, the flood risk management plans, the river-basin management plans and the drought plan as separate map modules.

The legal basis is Directive 2007/60/EC, transposed by Articles 169 to 171 of the Water Law of 20 July 2017 (Prawo wodne, Dz.U. 2017 poz. 1566, in force since 1 January 2018), with the content of the maps prescribed by the Regulation of the Minister of Maritime Economy and Inland Navigation of 4 October 2018 (Dz.U. 2018 poz. 2031). The minister responsible for water management approves the maps, and they enter into force by publication on the public information bulletin (BIP) websites, as electronic databases in shapefile format and as cartographic sheets in PDF and GeoTIFF cut to the 1:10 000 topographic sheet grid.

The practical result is unusually complete for the region: Poland has an official, downloadable hazard map with depth classes for every river reach identified as significant, plus separate scenarios for what happens if a levee or a dam fails. What it does not have is a map for the small streams and the pluvial flooding that fall outside the identified areas, and that is where terrain data and modeling take over. The sections below cover the planning cycles, the datasets themselves, the meaning of each scenario, the terrain model, the European layers, the reference floods and a working order for checking one address.

The Floods Directive cycles in Poland

Poland works in the six-year rhythm of the directive. Each cycle starts with a preliminary flood risk assessment (wstępna ocena ryzyka powodziowego, WORP) that identifies the areas of potential significant flood risk, continues with the hazard and risk maps for those areas, and ends with flood risk management plans (plany zarządzania ryzykiem powodziowym, PZRP). The third-cycle assessment was completed on 21 March 2025, and the third-cycle maps are being produced in two stages, the second of which covers the areas hit by the September 2024 flood.

powodz.gov.pl pages for the WORP, MZP and MRP and PZRP of each cycle; Directive 2007/60/EC for the cycle deadlines.

Source inventory

Every public dataset a flood-risk analysis of a Polish address can draw on, from the official national maps to the European layers that fill in the unmapped reaches. Where a publisher does not state a reuse license on the pages checked, the license column says so.

Compiled from the publishers named in the sources list; resolution, cadence and license as stated by each publisher.

What the scenarios mean

The Polish maps state hazard as an annual probability rather than a return period, and the portal is careful to say that a "hundred-year flood" is not a hundred-year schedule: each year carries a one-in-a-hundred chance. Three natural scenarios are prescribed for every mapped reach, and the maps add the engineered cases that matter in a country with a long levee network. Depth is always shown; velocity is shown for cities above 100,000 inhabitants.

Scenario definitions and depth classes from powodz.gov.pl "O mapach"; reach lengths from the third-cycle MZP and MRP page.

Terrain: the GUGiK 1 m model

Every Polish flood map is drawn on the national terrain model, and that model is one of the most open in Europe. GUGiK states that the primary digital terrain model (numeryczny model terenu, NMT) is a 1 m by 1 m grid derived from airborne laser scanning, with stereoscopic measurement in urban areas at a pixel of 10 cm or smaller, and that a 5 m grid version derived from 25 cm orthoimagery exists alongside it. The data are, in the publisher's words, available free of charge and for any use. They can be downloaded from the geoportal download module, viewed through WMS and WMTS services including a shaded-relief rendering, indexed by year through WFS, and pulled as raster through a WCS service that returns up to about 7 km² per request, in GeoTIFF or Arc/Info GRID.

The point clouds underneath are published too. GUGiK describes complete national coverage with airborne laser scanning at densities from 4 points per m² up to 20 points per m² in cities, distributed as compressed LAZ files that lose no information against LAS. Two vertical datums coexist: the older PL-KRON86-NH generation flown from 2010 to 2019 and the PL-EVRF2007-NH generation flown from 2018 to 2025, which is why the third-cycle flood maps are being recalculated to the new datum rather than only extended. The terrain model is updated systematically from annual surveys, so the vintage of a tile matters and the WFS index by year is the place to check it.

For flood work the terrain model does three jobs. It defines the floodplain geometry that the hydraulic models behind the official maps route water through. It resolves the small streams, road embankments and local depressions that a 30 m global model smooths away, which is the only route to a hazard estimate for the reaches the official maps do not cover. And because levees show up as raised linear features at 1 m, it allows defenses to be traced and their crest heights checked, which is what turns the levee-failure scenario from an abstraction into a line on a specific plot. The same tiles carry the building footprints and road embankments that decide whether water reaching a street reaches a ground floor, so a depth read from the official map can be refined to the doorstep rather than to the parcel centroid.

European and satellite layers

• JRC river flood hazard maps. The Joint Research Centre's gridded maps, issued on 8 March 2024 under CC BY 4.0, give water depth for nine return periods from 1-in-10 to 1-in-500 years on river basins larger than 150 km², at a grid of about 100 m, produced with the LISFLOOD hydrological and LISFLOOD-FP hydrodynamic models. The publisher states that they are not an official flood hazard map. They are useful for the Wisła, Odra, Warta and their large tributaries where a cross-border view is needed, but they ignore levees, which in Poland is the difference between a dry town and a flooded one.
• European Flood Awareness System (EFAS). The forecasting arm of the Copernicus Emergency Management Service produces river flood probabilities up to 15 days ahead, flash-flood indicators and seasonal outlooks. It is an early-warning product for authorities and registered users rather than a hazard map, and IMGW-PIB's own warnings remain the operational reference inside Poland.
• Copernicus Emergency Management Service mapping. Rapid Mapping delineates flooded areas for activated events and Global Flood Monitoring processes every Sentinel-1 radar pass into a systematic archive. Observed extents from the September 2024 Odra basin flood are the best public evidence for checking any Polish model against what actually flooded.
• EEA Flood Risk Areas Viewer. The European Environment Agency publishes the areas of potential significant flood risk that each member state has reported, which lets a Polish reach of the Odra or the Nysa Łużycka be compared with its Czech and German continuation.

Reference floods in the public record

The 2025 preliminary assessment catalogues 1,103 river floods between 1946 and 2023 and classes 304 of them as significant. Three events dominate the modern record, and each one reshaped the maps that followed it. The figures below come from encyclopedic summaries that cite Polish press and government statements; the assessment reports on powodz.gov.pl are the authoritative versions.

Wikipedia summaries citing Polish press and government sources; Wody Polskie preliminary flood risk assessment 2025 for the flood chronicle.

How to check a Polish address

A defensible flood-risk view of a single property takes six steps, each tied to one of the sources above.

1. 1

   Open the hazard map module on the Hydroportal

   Load the MZP module at wody.isok.gov.pl/imap_kzgw, find the parcel and read the extent for the 1 % scenario first, then the 10 % and 0.2 % scenarios. Read the depth class at the building footprint, not at the plot boundary.

2. 2

   Check the levee-failure layer

   If the plot lies behind a levee, the natural scenarios may show it dry. The levee-failure scenario shows what happens if that levee breaches, and it is the layer that insurers and lenders in levee-protected towns should be reading.

3. 3

   Read the risk map for consequences

   The MRP module turns extent into people, facilities and loss values per land-use class. It is the quickest way to see whether a flooded footprint is a garden or a hospital.

4. 4

   Confirm the reach is in the 2025 assessment

   Search the WORP library for the river and municipality. A reach that is not among the 1,336 river areas has no official map at all, which is not the same as no risk.

5. 5

   Look at the gauge

   On hydro.imgw.pl find the nearest station, its warning and alarm levels and the current stage; the warning archives on danepubliczne.imgw.pl show how often those levels have been reached.

6. 6

   Fill the gaps with terrain and satellites

   For unmapped streams, run the 1 m GUGiK terrain model; for large rivers outside the register use the JRC maps, remembering that they ignore levees; and compare any modeled extent with the Copernicus maps of September 2024.

How a model combines these sources

A property-level flood model treats the official maps as ground truth where they exist and as calibration targets where they do not: it attaches the Wody Polskie scenario extents and depth classes where an address falls inside a mapped reach, routes modeled discharges over the 1 m GUGiK terrain for the streams the maps skip, carries the levee-failure layer as a separate signal, and scores the result against satellite-observed floods before any figure is published. Availability by market is listed on the coverage page.

Questions