Flood-risk data sources for Czechia: who publishes what, and how to use it

Three official layers, one terrain model

Czechia is unusual in Central Europe in that it has three separate, publicly documented flood-hazard products that answer different questions. The statutory flood zones (záplavová území) are administrative areas fixed by the water authority under the Water Act and tell you whether a plot is legally inside a Q5, Q20 or Q100 flood extent. The Floods Directive maps, produced for the Ministry of the Environment (MŽP) in six-year planning cycles, add depth, velocity and a Q500 scenario for the stretches of river that carry significant flood risk. The insurers’ map, run for the Czech Insurers’ Association (ČAP) by Intermap Technologies, condenses hydraulic modeling into four risk zones that member insurers use when pricing property cover.

All three are built on the same upstream inputs: N-year discharges and gauge records from the Czech Hydrometeorological Institute (ČHMÚ), hydraulic studies commissioned by the five river-basin state enterprises (Povodí), and the national airborne laser-scanning terrain model DMR 5G published by the Czech Office for Surveying, Mapping and Cadastre (ČÚZK). Two European layers, the JRC river flood hazard maps and Copernicus Emergency Management Service (CEMS) satellite products, are useful for cross-checks and for observed flood extents, but they are explicitly not official maps for Czech territory.

The practical consequence is that a single address can carry three different labels: outside any statutory zone, inside a Floods Directive Q500 extent, and in ČAP zone 2. None of those is wrong. They describe different return periods, different modeling assumptions and different legal weight, and the sections below explain which one to trust for which purpose.

Source inventory

The datasets a Czech flood assessment should start from, with the publisher of record, what each one actually contains and how it can be obtained.

Publisher pages linked in the sources list; cadence and license as stated by each publisher on the date of writing.

Statutory flood zones: Q5, Q20, Q100 and the active zone

The legally binding layer is the záplavové území defined in Section 66 of the Water Act (Act No. 254/2001 Coll.). The VÚV TGM metadata record describes it as an administratively designated territory that may be flooded during a natural flood, which the water authority (vodoprávní úřad) must determine on the basis of a proposal from the watercourse administrator. In practice the proposal comes from the relevant Povodí state enterprise, backed by a hydraulic study, and the zone is drawn for the 5-year, 20-year and 100-year discharges. Within the Q100 extent the authority also delineates an active zone (aktivní zóna záplavového území), the strip where flow is concentrated and where new construction is restricted.

The aggregated national copy of these zones is DIBAVOD, the Digital Base of Water Management Data maintained by the GIS department of VÚV TGM. Its flood category holds six layers: Q5 (D01), Q20 (D02), Q100 (D03), the largest recorded natural flood extent (D04), the active-zone boundary for Q100 (D05) and Q500 (D08). The download page dates the Q5, Q20, Q100, active-zone and Q500 layers to 30 October 2025 and provides them as zipped shapefiles; the HEIS catalogue record for the same dataset states a scale of 1:10 000, WMS and WFS services and a CC BY 4.0 license with attribution.

Two cautions come from the publisher itself. First, DIBAVOD is an aggregation of individual determinations that were drawn at different times with different methods, so neighboring stretches can join awkwardly. Second, every flood layer carries the warning that the outline is orientational only and that binding information must be obtained from the watercourse administrator or the local water authority. For a legal question about a specific parcel, the determination document held by the water authority is the record, not the shapefile.

A Q500 layer exists in DIBAVOD but has no statutory force; it is carried because the Floods Directive cycle models a 500-year scenario and because several Povodí studies computed it. Treat it as a hazard indication, not as a zone with planning consequences.

Floods Directive maps and planning cycles

Czechia implements Directive 2007/60/EC through six-year cycles. The Ministry of the Environment publishes the resulting hazard, threat and risk maps in its Central Data Store (CDS) and the areas of significant flood risk in POVIS; the third-cycle draft plans for 2028–2033 were put to public consultation on 3 September 2026 with comments open until 28 February 2027.

MŽP press release of 3 September 2026; CDS "O datech"; POVIS2 public section.

The ČAP insurance flood map: four zones and what sits behind them

The Czech Insurers’ Association acts as expert guarantor of a flood-map system that Intermap Technologies builds and operates. It was opened to the public in January 2009 and made free for private use from May 2010; a basic zone check remains free for individuals, an extended property report has been a paid service since 1 February 2023, and commercial use requires a contract with Intermap. The zone meanings below follow the public descriptions of the map; the exact thresholds have changed between generations.

The insurers’ map is worth understanding in more depth than its four labels suggest, because its inputs are now closer to a full hazard model than to a simple buffer. According to ČAP, the RZ2023 generation, built in 2022 and 2023, used the state terrain model DMR 4G, N-year discharges from more than 200 ČHMÚ gauging stations, information on about 9 000 km of flood-protection structures and 2D hydraulic modeling that yields flow velocity and duration as well as depth. The earlier public descriptions record a coverage threshold of catchments above 20 km² and detailed 1:10 000 plans for around 200 of the largest towns.

In February 2026 ČAP announced the next step: a sixth generation of river maps and a second generation of flash-flood (přívalové povodně) maps, commissioned by eight member insurers. The river component reclassifies several N-year discharges, adds bridge profiles as flow obstacles, extends 2D velocity modeling to roughly 100 major watercourses and was validated against anonymized claims from the September 2024 floods. The flash-flood component uses a terrain model with about 20 cm precision, building footprints for water routing and new soil-hydrology (CN) maps from VÚMOP. The simplified tariff zones TZ1 to TZ4 combine flood type, return period, inundation depth and velocity, and now incorporate the full flash-flood map.

Because zone boundaries are proprietary and the underlying depth grids are not published, the ČAP map is the right tool for anticipating an insurer’s reaction to an address and the wrong tool for engineering, planning or independent modeling. Member insurers also retain discretion to deviate from the standard zone based on their own strategy and data, so the zone is an input to pricing rather than a rule.

cap.cz/povodnove-mapy; archiv.cap.cz; GISportal (2012); oPojištění.cz (2010).

Hydrology from ČHMÚ and Povodí, terrain from ČÚZK

The ČHMÚ flood reporting and forecasting service (HPPS) is the operational backbone. It publishes real-time stages in centimetres and discharges in cubic meters per second from the national gauge network, the three degrees of flood activity (SPA 1 vigilance, 2 alert, 3 emergency) reached at each profile, hydrological forecasts, the history of SPA exceedances, groundwater levels and a flash-flood risk product. Stations are grouped by the 14 regions, seven ČHMÚ branch offices and nine river-basin areas; most are operated by ČHMÚ itself, with the rest run by Povodí enterprises and other partners. Operational values are transmitted without full quality control and are later verified, so official statistics should be taken from validated series rather than from the live map.

The design values behind every statutory zone are the N-year discharges (N-leté průtoky) that ČHMÚ derives for gauge profiles and provides as standard hydrological data. ČHMÚ also curates the historical record: its Krolmus-MEF application maps extreme floods back to 1374 and documents flood marks such as the carved gauge on the Děčín Castle rock, which matters when a study needs to know whether a modeled Q100 has ever actually been exceeded on a reach.

The five river-basin state enterprises, founded by the Ministry of Agriculture, are the watercourse administrators for the main rivers and therefore the bodies that commission hydraulic studies, propose flood zones to the water authority and build and operate flood-protection measures. Povodí Moravy, for example, states that it watches 3 800 km of watercourses and 30 dams around the clock; Povodí Labe links directly to the CDS hazard maps and to the national flood-zone viewer from its home page. Their dispatch centres issue situation reports during events, which is the fastest source for what a specific weir or reservoir is doing.

Terrain comes from ČÚZK. DMR 5G is a bare-earth model stored as a triangulated irregular network of points from airborne laser scanning flown between 2009 and 2013 and completed for the whole 78 866 km² of the country on 30 June 2016. Its stated total mean height error is 0.18 m in open terrain and 0.30 m under forest, it is delivered in S-JTSK (EPSG 5514) with Baltic-after-adjustment heights, and it is distributed as LAZ tiles, through an ATOM feed and as a WMS, free of charge under CC BY 4.0. ČÚZK keeps it current through digital stereophotogrammetry and selective re-scanning. For any hydraulic modeling of small streams this is the layer that decides where water goes, and its accuracy is the reason the ČAP flash-flood maps can quote roughly 20 cm precision.

European layers: JRC, Copernicus and the EEA

Three EU products complement the national ones. They are consistent across borders, which the Czech maps are not, but they are coarser and carry no legal standing.

• JRC river flood hazard maps. The Joint Research Centre’s gridded maps cover Europe and the Mediterranean basin for nine return periods from 1-in-10 to 1-in-500 years on river basins larger than 150 km², with cell values giving water depth in meters. They are produced with the LISFLOOD hydrological and LISFLOOD-FP hydrodynamic models used by the European Flood Awareness System, are released under CC BY 4.0 and, in the publisher’s own words, are not an official flood hazard map. The grid is roughly 100 m, so they resolve the Labe, Vltava, Morava and Odra but not the tributaries that caused most of the 2024 damage.
• Copernicus Emergency Management Service. CEMS provides free-of-charge satellite mapping for natural hazards, including on-demand rapid mapping of flood extents during activations and the EFAS and GloFAS forecasting systems. Observed extents from Sentinel imagery are the best public evidence for validating any model against what actually flooded, and the September 2024 event in the Odra basin was mapped this way.
• EEA Flood Risk Areas Viewer. The European Environment Agency publishes the areas of potential significant flood risk and related Floods Directive reporting submitted by member states, which lets a Czech stretch be compared with its Polish or German continuation across the border.
• Copernicus Land elevation and hydrography. Where DMR 5G is not needed, the pan-European Copernicus DEM and the EU-Hydro river network provide a consistent lower-resolution base for catchment delineation and cross-border reaches.

The events that shaped the maps

Each large flood since 1997 has been followed by a rebuild of the official products, and the figures below are the ones the public record most often cites. They come from encyclopedic summaries that cite Czech press and government statements; the underlying ČHMÚ and MŽP evaluation reports are the authoritative versions.

Wikipedia summaries of the 1997, 2002, 2013 and 2024 floods (citing Czech press and government sources); ČAP press release of 2 February 2026.

How a model combines these sources

A property-level flood model built from public data treats these sources as layers of evidence rather than as one answer. The statutory Q5, Q20 and Q100 zones and the Floods Directive Q500 extents set the return-period envelope; the DMR 5G terrain and ČHMÚ N-year discharges allow depth to be modeled on the small streams that official maps skip; observed CEMS extents are held back as a validation set; and the ČAP zone is carried as a separate signal of how insurers will price the address. This is the approach Bytero takes when it scores an address, with each layer kept traceable to its publisher and vintage. Availability by market is listed on the coverage page.

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