Create Decorator 
To use this event use the following import:
groovy
import net.minecraftforge.event.terraingen.BiomeEvent.CreateDecoratorSub-Classes 
This event extends the following events and can use all their methods and fields: 
BiomeEvent
Methods 
groovy
net.minecraft.world.biome.BiomeDecorator getNewBiomeDecorator()groovy
net.minecraft.world.biome.BiomeDecorator getOriginalBiomeDecorator()groovy
void setNewBiomeDecorator(net.minecraft.world.biome.BiomeDecorator arg0)