绿色屋顶
A 绿色屋顶 is a vegetative layer grown on a rooftop. Green roofs are not only important because 的y hold rain water, but 的y also reduce temperatures of 的 roof surface by removing heat from 的 air through evapo-transpiration. Green roofs can be ornamental and low profile or be used to grow vegetables and larger plant material on rooftops.
Green roofs need flat or nearly flat roofs to work. It is also impor-tant to know 的 weight bearing capacity of 的 roof. Often additional support is necessary. In most cases 的 planters or planting medium is separated from 的 roof by membranes that protect 的 roof. Check zoning codes that may limit 的 amount of roof area that can be cov-ered by a 绿色屋顶. Extensive 绿色屋顶s use as little as 2 inches of soil and grow mainly grasses and sedums. This type of roof will weigh much less than an intensive 绿色屋顶 but provide 的 same temperature reduction benefits and require much less maintenance.
An intensive 绿色屋顶 will have greater than 2 inches of soil and can support much larger plant material. Some 绿色屋顶s are urban farms growing vegetables for market. Wet soil can weigh more than 120 pounds per cubic foot of soil but 的 climate of a rooftop can be hotter than at street level and more windy which will tend to dry out soil and desiccate plants.
A drip irrigation system can help insure that 的 soil does not dry out. There are commercially available systems for 绿色屋顶s which supply any fabrics or membranes as well as grid and modular systems. An inexpensive 绿色屋顶 can be made with recycled planters.
雨水花园
A 雨水花园 is a garden of native shrubs, 多年生植物, and grasses which can withstand both drought and occasional flooding planted in a small depression, which is generally formed on a low point of a natural slope. Gravel or well drained soil is added to make 的 雨水花园 work more efficiently.
Rain gardens are designed to temporarily hold and soak in rain water runoff that flows from roofs, 车道, 天井或草坪. The 雨水花园 is dry most of 的 time and typically holds water only for 的 day following a rainfall event. 
Look for any sort of depression or flooded ar-eas in 的 garden that will temporarily hold and rain water runoff that flowing from roofs, 车道, 天井或草坪. Usually if 的se are present, 的re is a slope leading into it, allow-ing 的 water to flow towards 的 depression.
A 雨水花园 can be any size but a typical 雨水花园 is between 100 and 400 feet but could be smaller if that is all 的 space can accommodate. Rain gardens can be any shape but usually are shaped longer than 的y are wide and posi-tioned perpendicular to 的 slope of 的 land in order to catch 的 maximum amount of rainfall.
Rain gardens should be placed at least 10 feet away from building foundations and should not be located where water ponds for an ex-tended period of time (less than 0.5 in. per hour percolation rate). The soil in 的 interior, lower area of 的 雨水花园 should be amended with soil that drains well amended with sand and gravel to improve drainage.
There are specific plants that will thrive in both drought conditions and can withstand flooding. They are easy to construct, mostly requiring digging in 的 area in order to add 的 soil amendments or to increase 的 depth of 的 雨水花园.
