Step 1: Context of the event.
The 2013 Uttarakhand floods were caused by heavy rainfall and cloudbursts, severely affecting the region.
Step 2: Explanation.
Kedarnath temple, located near the Mandakini river, was one of the most affected religious sites, though the shrine itself remained mostly undamaged.
Step 3: Conclusion.
Hence, the temple affected was Kedarnath.