Rippled surface on lake ends abruptly

[greypilgrim]

Hi.

I've made these pictures on Reichenau Island in Lake Constance, Germany. I was suprized about that clear line between the calm area close to the shore and the more rippled surface further out. The wind was weak, but directed from water to land.

From a pier I could see that the ground drops abruptly by 1-2 meters just about under that line. But how could this possibly affect those small surface ripples that much?

 

[jrmichler]

The bottom has little, if any, effect on waves if the water is deeper than the distance from one wave crest to the next. The figure below is from Limnology, Third Edition, by Robert Wetzel:

Is there a tree line near the water's edge that blocks the wind such that the wind velocity drops at the water surface where the waves stop?

 

[davenn]

I've made these pictures on Reichenau Island in Lake Constance, Germany. I was suprized about that clear line between the calm area close to the shore and the more rippled surface further out. The wind was weak, but directed from water to land.

Hi,
I have seen this so very often over the years. The breeze is just blowing across areas of the water. If you watch long enough,
you will see the wind affected areas moving around on the water.
As a result some of the water is in the breeze, some isn't.Dave

 

[DaveC426913]

Agree. Those ripples are caused by light breezes touching the water surface. Sailors use these to spot and anticipate puffs.

The correlation with bottom features is surely coincidental and temporary.