Hopefully, you have gone online, out in nature, or in architectural magazines to gather ideas of the return(s) you want to build. However, just a “stream” or “waterfall” isn’t going to cut it. There many types of both! There are many subtle differences and definitions out there for return types with many being subjective. These descriptions are a generalization.
Slope: As discussed in the previous article, slope determines water flow (current). However, it also describes different watercourse types. Streams and falls are sometimes based upon the slope of the channel. To rate a slope, we focus on the rise and run (like stairs). How far you travel horizontally is the run and how much the elevation changes vertically within that distance is the rise. For instance, level is NO elevation change in a 1’ run (flat). Minimum slope to move water should always be a ¼” per foot. Meaning over 4’, one inch is gained. When laying out a watercourse, start at the lowest point and multiply the total length by this “rise” figure. For example, if you want a 12’ watercourse to be nearly flat, multiply ¼” by 12 which equals a 3” rise. Therefore, the highest point of the stream needs to be 3” higher than the lowest point. Remember, you can alter the slope, depth and width throughout. I have broken slope down as follows:
- Skewed: Rise is ¼” to 2½” per foot (~5°: rise is nearly flat). Water moves slowly with minimal disturbance (1.2° - 11°).
- Slight: Rise is +2½” to 8” per foot (~22½°: rise is half of run). Water moves briskly with some disturbance (12° - 34°).
- Slanted: Rise is +8” to 18” per foot (~45°: rise equals run). Water move fast with moderate disturbance (35° - 56°).
- Steep: Rise is +18” to 60” per foot (~67½°: rise is twice of run). Water churns with incredible disturbance (57° - 79°).
- Sheer: Rise is +60” per foot (~85°: rise is nearly vertical). Water tumbles or falls free and breaks apart with air (80°+)
- Angles: Skewed: ~5°=1:12, Slight: ~22½°=5:12, Slanted: ~45°=12:12, Steep: ~67½°= 29:12, Sheer: ~85°=137:12
Stream Anatomy: Basically, this is a long trough covered with a liner that runs from point A (headwaters) to point B (the mouth). The headwater will be at a greater elevation than the mouth. Watercourses vary in depth, width and slope. They may be filled with rocks (more disturbances) or devoid of them. Flat water is very still flow in the streambed while riffle is ripples or rolling waves caused by underwater bed obstructions. A knickpoint is a sudden change to the angle of the bed. This results in a change from one stream type to another or falls. Slopes range from skewed, slight to slanted. *NOTE: The three streambed types Cascade, Scree and Slide may be classified as waterfall types (not streams) when on a steep slope of over 56° (57° - 79°) – a transition from streambed to falls.
- Stream: A watercourse that has a nearly equal width and depth. Slope varies from skewed to slight (1.2° to 22½°).
- Brook: A watercourse that is typically twice as wide as it is deep. Slope varies from skewed to slight (1.2° to 22½°).
- Creek: A watercourse that is typically twice as deep as it is wide. Slope varies from skewed to slight (1.2° to 22½°).
- Rapid: A greater sloped stream with nearly equal width and depth. Slope varies from slight to slanted (23° to 45°).
- Whitewater: A greater sloped brook being twice as wide as it is deep. Slope varies from slight to slanted (23° to 45°).
- Chute (Flume): A greater sloped creek being twice as deep as it is wide. Slope varies from slight to slanted (23° to 45°).
- *Cascade: A greater sloped rapid with nearly equal width and depth. Slope varies from slanted to steep (46° to 67½°).
- *Scree: A greater sloped whitewater being twice as wide as it is deep. Slope varies from slanted to steep (46° to 67½°).
- *Slide: A greater sloped chute (flume) being twice as deep as it is wide. Slope varies from slanted to steep (46° to 67½°).
Streams versus Waterfalls: Basically, falls are streams running down a steep or sheer slope (OR when the water leaves one feature and falls free into another – this will be dealt with in the next section). Like streams, falls vary in depth, width and slope. They may be filled with rocks or devoid of them. Like streams, there are many terms to describe the anatomy of a waterfall (all with nuanced terms). The transition from a stream to a falls is very subjective and is in the eye of the beholder.
Previous Article: Water Returns – Evaporation
Next Article: Water Returns – Falls