The valve is changing. Compare the image in the post below from July 2013 with this image from April 2006 and with that image from August 2005. Especially the 2005 image, taken from the other end of the loch, indicates radical changes in the shape of the peninsulas. From memory, the valve was only slightly broader in August 2009 and images from 2011 show the same. Equilibrium my ass. What might happen here is a superposition of annual variations in the water level with a long-term evolution of the loch morphology due to ongoing sedimentation. One has to watch this.