If you have high water flow on a slope in a ditch line or drainage swale, you can choose a round stone (river rock) or a crushed granite product. Product size is subjective and based on the volume of water and the steepness of the slope you are dealing with. For a lower degree of slope or lower volume of water, you can choose a smaller River Rock (1-3”) or smaller 2” clear crushed granite. For a higher degree of slope or higher volume of intermittent water, you can choose larger River Rock (4-6”) or larger 4” or 6” clear stone crushed granite.
This is a personal and subjective question. The following is only our subjective view. Smaller (1-3”) River Rock has a more clean look and is easier to maintain (i.e. leaves). Therefore as an example we recommend and use it around perimeters of buildings under the drip edge. Larger (4-6”) River Rock has a more natural look. As an example, we use it as a practical use for areas with higher intermittent water flows over a geotextile as a Natural Rip Rap. You can mix in larger pieces to mimic a natural dry stream bed.
Creating a clean environment up against a building is important for the health and maintenance of a building. Therefore we recommend a clear stone product against a building and most commonly recommend 1-3” river rock for its aesthetic quality and ease of maintenance. It is common practice, particularly in heavily treed cottage areas, to not install eavestrough. We recommend river rock over geotextile; 1.) to create a SPLASH GUARD and keep the cladding of the building clean, 2.) to protect from EROSION and direct the water away from the building (at times, we recommend a compacted Granular base layer be placed below the river rock and graded away from the building, as the water travels through the river rock, it will travel across the compacted granular away from the building) and 3.) To MINIMIZE INSECTS. Pest control specialists believe river rock helps to deter insects such as ants away from entering a building, in particular over that of mulch and soil.