Blurry lines between textures using image masks

[ridley1224]

I'm trying to create a golf course. I use a black and white alpha for the image masks for each texture for the fairways, greens, and sand traps. The textures have blurry transitions between them. How do I get a solid border around each texture on the terrain using the masks?

Example image masks

Fairways

Greens

[Bryan]

Can you change the strength transform to a flat line