Flood Wolfenschiessen (2005)

The heavy rainfall of summer 2005 caused both floods in the vicinity of lakes and rivers and landslides and debris flows on water-soaked slopes. Picture: Rutschung und Überschwemmung in Büren ob dem Bach, Schweizer Luftwaffe 23.08.2005

Bank erosion involves the eroding of bank material along the side of a water course and in the channel bed. The frequency and extent of lateral erosion in mountain and valley rivers during the storm of 2005 had never before been observed in Switzerland. The extent of the bank retreat is very visible in this photograph. The bank retreat is measured in metres. Picture: Bank erosion Wolfenschiessen, Kanton NW 27.08.2005

The precipitation experienced in the south-eastern part of the commune of Wolfenschiessen was that of an approximately 100-year return period. The streams on the right side of the valley increased massively in size and the interaction of slope and channel processes caused extreme events resulting in large debris flows in Oberrickenbach in particular. It was not possible to establish in some torrents whether the processes involved were fully formed debris flows or debris-flow-like discharges with high concentrations of solid materials. This photograph shows the consequences of one of the three biggest debris flow events in the Haldibach stream in the commune of Wolfenschiessen. Picture: Überflutung eines Badezimmers in Oberrickenbach, Kanton NW 31.08.2005

Bed load deposits caused a reduction in discharge capacity and, as a result, floods arose on the river Engelberger Aa. Entire settlements and agricultural land were flooded. It is difficult to identify on this photograph where the riverbed of the overflowing Engelberger Aa was originally located. Picture: Überschwemmte Fläche in Wolfenschiessen, Kanton NW 24.08.2005

The mountain torrents caused floods involving water and bed load, overbank sedimentation and debris flows. In addition to the effects of the water, the flow rate, bed load and driftwood exacerbated the damage caused. Picture: Geschiebeablagerung im Haldibach, Kanton NW 07.09.2005

Prior to the storm of 2005, the Schmidsboden area was not known as an area subject to landslide activity. Despite this, a landslide occurred in the course of the storm of 22 August 2005. It caused three major debris flows which eroded additional material while on the move. As a result, the size and speed of the debris flows increased from one event to the next. Schmidsboden suffered extensive damage as a result. A small stable was completely destroyed, a large stable severely damaged and the farmhouse was also damaged. Parts of the protective forest and agricultural land were also destroyed. Picture: Zerstörung eines Stalls in Oberrickenbach, Kanton NW 31.08.2005

The very deep major landslide in Schmidsboden had a fracture depth of 10 m and the depth of the rupture surface was 20m. The primary landslide process presumably took place in several stages from the top to bottom of the slope. The landslide caused a blockage of up to 30 m in the Haldibach stream which flows at the bottom of the slope. The total volume of the sliding mass was estimated at 250,000 m³. The area had not previously been identified as vulnerable to landslides. Picture: Tiefgründige Rutschung in Oberrickenbach, Kanton NW 30.08.2005

All of the landslide processes in the canton of Nidwalden occurred within a 24 hour period. The temporal phasing of the landslides within the canton of several hours was observed. The landslide activity appeared to correlate with the precipitation volume and reached its peak level during or shortly after the peak in precipitation. From a spatial perspective, the landslides were concentrated in known landslide areas. The slope gradient was evidently not the only crucial factor in the triggering of the landslides. In many cases, underground water discharge along geological layers, from crevices or karst holes played a major role in the process. These underground water discharges were an important trigger of slope processes during the storm of 2005. Picture: Rutschungen in der unteren Ifängi, Kanton NW 30.08.2005

Several parts of the Engelberg branch, i.e. between Dallenwil and Engelberg, of the Zentralbahn railway track in the canton of Nidwalden were badly damaged. As a result of the flooding and lateral erosion of the Engelberger Aa, in many places the Zentralbahn's catenary line, tracks and substructure were destroyed. Picture: Zerstörtes Bahngeleise in der Rappenschwändi, Kanton NW 31.08.2005

The Buochserhorn civil defence company was deployed in the repair of the Zentralbahn railway network in the Engelbergertal valley. The Zentralbahn railway network was severely damaged and even destroyed in several locations. With the exception of the section of railway near Fangbach/Reinerts (Obermatt) and a small location near the Buoholzbach stream, the damage to the Dallenwil - Engelberg section of the railway was all caused by the Engelberger Aa. Around 80% of the rail network was out of service in the immediate aftermath of the flood. The tracks and signal equipment had to be cleaned and repaired. Picture: Wiederinstandstellung der Zentralbahngeleise in Wolfenschiessen, Kanton NW 30.08.2005

The intensive precipitation transformed both the river Engelberger Aa and nearby streams into raging torrents that transported large volumes of bedload, debris and wood into the valley and burst their banks in places. Many streams caused extensive damage in the form of debris flows. The Haldibach, Buoholzbach and Seklisbach streams in the commune of Wolfenschiessen were particularly prominent among them. The rail network of the Zentralbahn railway in the commune of Wolfenschiessen was very badly damaged and even destroyed in parts.