The Mighty Elbe: A Lifeline and a Potential Hazard

The Elbe River, a major European waterway, originates in the Czech Republic and traverses through eastern Germany, including key cities like Dresden, Dessau, Magdeburg, and Wittenberge, before emptying into the North Sea near Brunsbüttel.Its extensive reach also impacts Schleswig-Holstein and Lower Saxony. while the Elbe is vital for transportation and commerce, it also poses a meaningful flood risk to the communities along its banks.

Understanding Flood Dynamics: Key Indicators and Levels

Decoding Water Level Terminology

To effectively monitor and prepare for potential floods, it’s crucial to understand the terminology used to describe water levels. These values are calculated based on historical data, providing a baseline for assessing current conditions.

• Mean Water Level (MW): The average water level over a specific period, offering a general sense of the river’s state.For the Elbe near Dresden (2010-2020), it’s 156 cm.
• Mean Low Water Level (MNW): The average of the lowest water levels recorded over a period. For the elbe near Dresden (2010-2020), it’s 67 cm.
• Mean High Water Level (MHW): The average of the highest water levels recorded over a period, notably relevant in tidal areas. For the Elbe near Dresden (2010-2020), it’s 458 cm.
• Lowest Low Water Level (NNW): The absolute lowest water level ever recorded. For the Elbe near Dresden,this stands at a mere 21 cm.
• highest High Water Level (HHW): the record-breaking highest water level ever observed. The Elbe near Dresden reached a staggering 940 cm during the devastating floods of August 17, 2002.
• Highest Shipping Water Level (HSW): The maximum water level at which navigation is still safe. For the Elbe near Dresden, this limit is 500 cm.

Critical Levels in dresden: When Does the City Flood?

In Dresden, the Terrassenufer (Terrace Bank) is typically the first area to be affected by rising Elbe waters, ofen requiring closure when the water level exceeds 5.5 meters. As the water continues to rise, access points to the Elbe in areas like Mickten and Johannstadt become submerged, and the Pieschener Allee is also prone to flooding.

To mitigate the impact of more severe flooding, mobile flood barriers are deployed. The gate on Weißeritzstraße is activated at 6.10 meters, while the flood protection gate at the Ostraufer is closed at 7 meters.

Flood Warning System: Understanding Alert Levels in Saxony

Saxony employs a four-tiered flood warning system, each level triggering specific actions and indicating the severity of the situation:

• Alarm Level 1: minor flooding. This marks the initial stage, with the river beginning to overflow its banks.
• Alarm Level 2: Moderate Flooding. Grassland and forested areas start to flood, and the water reaches the base of dikes.
• Alarm Level 3: major Flooding. Individual properties, streets, and cellars are inundated. polder areas may experience backflow from drainage systems, and water levels reach up to half the dike height.
• Alarm Level 4: Severe Flooding. Large areas, including roads and infrastructure in built-up zones, are submerged.

It’s important to note that flood warning levels and response protocols can vary between different federal states in Germany.

Staying Informed: Flood Warning Channels

In Germany, the responsibility for issuing flood warnings is governed by the Civil Protection and Disaster Relief Law (ZSKG). While various entities, including the federal government, state authorities, police, and fire departments, can issue warnings, the primary role typically falls to the state flood centers.

These centers monitor water levels and issue official warnings when risky conditions arise. The public can also access real-time facts through the Cross-border Flood Portal (LHP).

Warnings are disseminated through various channels, including:

• Radio and television broadcasts
• Loudspeaker announcements
• Sirens
• Local newspaper and radio station websites
• Warning apps (e.g.,NINA,KATWARN)
• Social media platforms
• Digital advertising boards
• Door-to-door notifications

It’s crucial to remember that not all channels are used simultaneously,and availability may vary by location. The city of Dresden provides updates on current flood-related measures on its website: www.dresden.de/hochwasser.

Looking Upstream: Monitoring Water Levels at Schöna

Water levels at Schöna, and also in Czech Usti Nad Labem, serve as an early indicator of potential flooding in Dresden. By monitoring these upstream locations,experts at the State Flood Center can better forecast Elbe levels in Dresden,taking into account other relevant factors.