Rems and Winterbach · River, water, nature and history

Heavy rain in Winterbach

A flood announces itself: the Rems rises over hours, the Schorndorf gauge shows it, the retention basin at Ostlandstraße closes its gates. Heavy rain hardly announces itself at all. A thunderstorm stalls over the Schurwald, and a quarter of an hour later water and mud run through streets where there has never been a stream. More than half of all flood damage in Germany is now caused by heavy rain, writes the municipality of Winterbach. This page explains when rain becomes dangerous, what the official maps for Winterbach show and what everyone can do themselves. Where the water comes from and where it flows is described on Water in Winterbach.

How much is a lot?

One millimetre of rain is one litre per square metre. 100 litres per square metre means: if nothing ran off and nothing soaked away, the water would stand ten centimetres deep on every square metre. Whether an amount is dangerous depends on the time in which it falls. The German Weather Service (DWD) warns in these levels:

Continuous rain is judged over longer periods: warning level 2 from 30 litres in 24 hours, extremely abundant continuous rain from more than 80 litres in 24 hours. The calculator places any amount – for example a thunderstorm over the catchment of the Lehenbach (about 7 square kilometres).

The heavy-rain hazard maps for Winterbach

For all municipalities in the Rems Water Board (Wasserverband Rems), the board commissioned heavy-rain hazard maps, prepared by the engineering firm geomer. The maps for Winterbach were available in December 2024 and were presented publicly in the Lehenbachhalle on 22 January 2025. They are the first step of municipal heavy-rain risk management according to the state guideline: the hazard analysis is followed by a risk analysis and an action plan.

What the maps show. A computer model lets an imagined heavy rain fall on the terrain model and calculates where the water flows on the surface and where it collects. The maps show the maximum flood depth – the darker the blue, the higher the water – and the flow velocity. This makes the runoff paths visible: the routes along which hillside water finds its way over meadows, paths and roads, and the hollows where it stays.

Three scenarios. Under the state guideline, three cases are calculated: a rare event (one-hour rain of the kind that statistically occurs about every 30 years), an exceptional one (about every 100 years) and an extreme one with 128 litres per square metre in one hour – as much as fell in the 2016 storm at Braunsbach. For Winterbach, the municipality provides the maps for the exceptional runoff event as PDFs in five sheets; the interactive map for the Rems municipalities is run by geomer.

How to read the map. It is best to find your own house and check whether a runoff path leads towards it, whether the plot lies in a hollow and where the water would arrive at basement stairs, light wells and garage entrances. The maps show a model calculation, not a forecast: blocked inlets, debris on screens or opened gates are unknown to the model. We deliberately do not produce our own hazard map; only the official one is binding.

Heavy-rain hazard maps of the municipality of Winterbach (German) (opens in a new tab) · Interactive map for the Rems municipalities (German) (opens in a new tab)

Where rainwater runs on the slopes and how far the Rems can rise in a flood is shown on our flood map. The flow paths are calculated from the terrain model and are not a hazard map – the official maps are binding.

What has happened in Winterbach

1 to 3 June 2024. After days of rain the retention basin at Ostlandstraße filled to the brim twice; at the same time the streams burst their banks: under the village centre the Lehenbach pushed up manhole covers, the Bücklensweilerbach flooded the underpass in Westergasse, and the Krebsbach and Wattenbach overflowed too. → Flood protection on the Rems

19 July 2025. On Saturday evening a thunderstorm brought about 40 litres per square metre within a short time. At the Lehenbach, debris jammed at the inlet to the culvert and the water rose; the fire brigade was called out to several places.

4 August 2025. Heavy rain again, this time at the Wattenbach: it was on the verge of overflowing into the industrial estate, basements filled with water; the fire brigade pumped them out and watched the vulnerable spots in the Oberdorf. A few days later the deputy fire chief said of these call-outs: "The warning time was zero."

The three events show the two faces of water in Winterbach: in June 2024 a Rems flood and heavy rain came together; in summer 2025 the Rems was low – and still the streams overflowed. Heavy rain is a problem of the small valleys and slopes, not of the river.

The Lehenbach reservoir

The Lehenbach is the largest stream that joins the Rems in Winterbach: its catchment covers about 7 square kilometres, a good third of the municipal area. South of the village, the Lehenbach reservoir has held it back since 1963/64 – a flood retention basin with an 18-metre earth dam and a permanent pool used as a fish pond. According to the LUBW register of installations, the basin holds about 452,000 cubic metres in a flood; above the dam lie 5.8 square kilometres of catchment.

A rough calculation shows what that means: 40 litres per square metre on 5.8 square kilometres are about 230,000 cubic metres – the basin can take such a rain if it is empty beforehand. Below the dam, however, a good square kilometre is added, much of it built up: there the water no longer passes through the reservoir but flows over roads and sewers directly to the stream. That is why the village centre is not safe from every heavy rain even with the reservoir.

Early warning on the streams

Since February 2025, radar sensors have been measuring the water level around the clock at three places: at the confluence of the Krebsbach and Wattenbach, on the Mönchsklingenbach at Bücklensweilerweg and on the Lehenbach before the culvert in the Oberdorf. The data go in real time to the town hall and the emergency services and are linked to FLIWAS, the state's flood information system. The sensors shorten the time until someone knows that a stream is rising – they cannot prevent it.

What everyone can do at their own house

Every owner is responsible for protecting their own building. In its leaflet on protection against heavy rain, the municipality recommends among other things:

• look at the heavy-rain hazard map for your own plot
• secure basement stairs, light wells and ground-level openings against water, and make windows and doors pressure-tight
• seal basement floors and walls
• install a backflow preventer so that water cannot be pushed from the sewer into the house

On top of that comes everything that holds water back on the plot: unsealing surfaces, letting rain soak away in hollows, green roofs – and, if a cistern is planned, one with a retention space and throttle. A pure watering cistern is often already full when heavy rain comes. → What is a retention cistern?

What this means for the Remswelle

For the wave, heavy rain is not a flood: the big Rems floods almost all come in winter and spring, when the soils are wet; summer thunderstorms hit the small streams. For us the topic belongs here all the same. Anyone who surfs on the Rems looks at water and weather every day – and sees that the same slopes that feed water to the river in summer turn into torrents within minutes in a thunderstorm. The better the landscape holds water, the less of it rushes down and the longer the Rems keeps flowing in summer. → Sponge landscape Winterbach · → Flood map with flow paths and catchments

Frequently asked questions

What is the difference between a flood and heavy rain?

A flood occurs when a river overtops its banks, usually after long rain across the whole catchment; it announces itself over hours. Heavy rain is a great deal of rain in a short time in one place. The water then runs off over the surface, even where there is no stream, and makes small streams swell within minutes.

From when does the weather service warn of heavy rain?

From 15 litres per square metre in one hour or 20 litres in six hours. More than 25 litres in one hour count as severe weather, more than 40 litres in one hour as extreme severe weather.

Where can I find the heavy-rain hazard map for my house?

On the website of the municipality of Winterbach under heavy-rain risk management, as PDFs in five sheets, and as an interactive map on starkregengefahr.de for the Rems municipalities (both in German).

Can a house far from the streams be affected?

Yes. Heavy rain runs off over meadows, paths and roads and collects in hollows. Houses at the foot of a slope, on roads that lead downhill or with low-lying entrances can be affected, even far from any stream.

What does the Lehenbach reservoir achieve in heavy rain?

It holds back the water from about 5.8 square kilometres above the dam, up to about 452,000 cubic metres. What falls below the dam – including a large part of the village – reaches the stream without passing through the reservoir.

Sources

• Deutscher Wetterdienst (German Weather Service): warning criteria for heavy rain and continuous rain (accessed 03.10.2026)
• Gemeinde Winterbach: Starkregenrisikomanagement; Starkregengefahrenkarten (five sheets, as of 23.01.2025); information event 22.01.2025 (presentation by geomer); leaflet "Schutz vor Starkregen" (accessed 03.10.2026)
• geomer GmbH: heavy-rain hazard maps for the Rems municipalities, starkregengefahr.de
• LUBW: Leitfaden Kommunales Starkregenrisikomanagement in Baden-Württemberg (scenarios rare, exceptional, extreme); register of flood retention basins (HRB Lehenbach: built 1963, retention volume 452,000 m³, catchment 5.8 km²); river catchments 1:10,000 – Grundlage: Daten aus dem UIS der LUBW, accessed 03.10.2026
• Netze BW: Frühwarnsystem für Hochwasser in Winterbach (NOYSEE, 2025)
• Zeitungsverlag Waiblingen: heavy rain 19.07.2025 (Lehenbach); 04.08.2025 (Wattenbach, industrial estate); 08.08.2025 ("no warning time"); June 2024 (flood in Winterbach)

Last updated: 15 October 2026 · Initiative Remswelle