https://blendermarket.com/products/terrain-creator

An addon for creating terrains quickly and simply, using a combination of procedural noise with drawing features that allow you to draw terrain features like mountains and valleys directly on your terrain for precise control over placement. Choose from a variety of presets to get started, draw your terrain features, customize material colors and settings, add and customize water level with generated shoreline, erosion simulation, foliage scatter, all combine to create an endless variety of terrains.