Complex sentence: On March 11,2011 the 2011 Tōhoku earthquake and tsunami occurred, with the earthquake causing ruptures in multiple water mains originating from the city's water supply, the Surikamigawa Dam, resulting in the majority of the city losing access to running water.
Split into simpler sentences: On March 11,2011 the 2011 Tōhoku earthquake and tsunami occurred, with the earthquake causing ruptures in multiple water mains originating from the Surikamigawa Dam, which supplies much of the city's water. This resulted in the majority of the city losing access to running water.