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Misinformation regarding the Seewiese flood retention basin has been refuted
Darmstadt. The city of Darmstadt, a center of science and research, is currently investigating the consequences of the heavy rainfall event of July 7, 2025, which led to flooded streets and basements in parts of the city. According to City Councillor Paul Georg Wandrey, damage reports from the public, fire department incident data, and measurements from the German Weather Service are being analyzed and compared with the city's standard operating procedures.
Since the incident, the city has been answering numerous inquiries about the Seewiese flood retention basin (HRB) – and refuting misinformation. "The HRB is not out of service and has not been abandoned to serve as a wild boar reservoir," Wandrey emphasizes. The basin, owned by the Schwarzbachgebiet-Ried Water Association, a green retention basin for several years . This mode of operation even increases the retention volume compared to a permanent impoundment.
Along the Ruthsenbach stream, there are several flood retention basins, which, according to water association managing director Georg Möhrle, were fully functional on July 7th. The outflow rates are regulated by fixed sluice gates to ensure the safe discharge of floodwater. No overflow of the Ruthsenbach stream has been reported.
The heavy rainfall is classified as an "urban flash flood," caused by intense precipitation in a heavily paved area. The water flowed primarily from paved surfaces in Arheilgen into the Ruthsenbach stream, which could no longer absorb the volume.
The water authority is also planning an ecological redesign of the Seewiese weir to restore fish passage. The permanent impoundment has been discontinued, and planning has been underway since April 2025. The permit application is to be submitted to the regional council in the fall. During the winter of 2025/2026, the removal of vegetation and sediment from the Ruthsenbach stream, as well as maintenance work on the weir, are planned.
(Darmstadt - Red/PSD/Stip)
