Waterfall overflow

Lovely feature blends nicely with natural stone wall.Several issues might be responsible.
The most obvious forgive me is that your pond is too full and overflows esp if you experience heavy rain . In raised ponds overflow pipes are often installed to discharge excess water discreetly.

You may also have a powerful pump that is drawing up a huge volume of water relative to size of pond.Try removing water from your pond in the first instance check your pump flow rate litres/hour should not need to be more than 2-2500 lires per hour if that.
All else fails drill hole in far corner insert platic pipe 3-4 inches below pond top and seal with silicone sealant.

Good luck will look great when planted up .Love the steps.

Thank you. The pond and terracing is actually built from the stones of an original and very old wall which went straight up from the path to a height of 5 ft. It became unstable and began to fall down last winter so we had the whole bank terraced back and the pond built as well. The pond is designed so that any excess water will soak back into the ground behind it.
I actually think that you maybe right - the man who constructed it for me may have installed too powerful a pump. Everything is fine if I have the waterfall and the fountain both on together. The problem only arises when I turn the fountain off and just have the waterfall.
I will try what you suggest.

Hi Judi yes that will increase water flow.I was advised not have a fountain and a cascade due to this increase in volume and as I also wanted water lillies that close up if (rain and)water from a fountain fall on them.

Took me so long to dig out my pond 22' x 16' all hand dug!
Have not yet installed pump as next stage is decking than attach pump to deck leg as it will jut out over the water. Well thats the theory .Best wishes.