Quick Answer
Assess your site by identifying the highest points and lowest points, and then determining the contour lines that run between them. Walk the property and note the existing topography, drainage patterns, and areas of water accumulation. This information will help you place swales effectively to harvest and manage rainwater.
Understanding Contour Lines
To assess your site, start by creating a topographic map or sketch. Identify the contour lines that run across your property, which are imaginary lines that connect points of equal elevation. Use a tape measure or a leveling tool to help you determine the elevation at different points on your property. Typically, contour lines are spaced 1-2 feet apart, but this may vary depending on the terrain.
Locating High and Low Points
Walk the property and identify the highest and lowest points. These areas will determine the flow of water across your land. High points, or ridges, can be used to create berms or swales that capture and redirect water to specific areas. Low points, or depressions, should be avoided for swale placement, as they may not be effective in capturing and storing rainwater.
Determining Swale Placement
Using your topographic map and knowledge of the contour lines, high and low points, determine the best locations for swale placement. Typically, swales are placed on contour lines, 1-2 feet below the surrounding terrain, to capture and store rainwater. Consider the slope and gradient of the land when placing swales, as steep slopes may not be suitable for effective water harvesting.
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