Since, rain gardens slow down the runoff it supports to retain water for a long time. But tropical countries get heavy rains some times and in some seasons raining happens for hours.
Are there special dimensions or special methodologies when this rain garden is engineered for such countries or places?
Well,
same concept can be applicated , the different is in the retention rate, which is obtained within storage change(ΔS) as mentioned in the following water balance equation according to the attached figure
P = ET +Δθ +D +Ro +ΔS F = ET+ Δθ+ D
groundwater recharge rate (D)
infilltration rate F
Rainfall rate P
Evapo-transpirationration rate - ET
Soil moisture content Δθ.
Runoff Ro
Storage change rate ΔS
Sincerely
The design (size, shape and plant species) will depend also on the characteristics of the soil as the purpose for having a rain garden is to collect the water which should percolate gently through the soil profile. Just to avoid water run off rain gardens are valuable in a variety of environments (especially in the the urban areas of the tropics).
I think yes. Please have a look at this useful ResearchGate link and PDF attachment.
https://www.researchgate.net/publication/258770785_Constructed_Rain_Garden_Systems_for_Stormwater_Quality_Control_under_Tropical_Climates
Main purpose of a rain garden is to improve water quality in nearby bodies of water and to ensure that rainwater becomes available for plants as groundwater rather than being sent through stormwater drains straight out to sea.
A rain garden is a garden of native shrubs, perennials, and flowers planted in a small depression, which is generally formed on a natural slope. It is designed to temporarily hold and soak in rain water runoff that flows from roofs, driveways, patios or lawns. Rain gardens are effective in removing up to 90% of nutrients and chemicals and up to 80% of sediments from the rainwater runoff. Compared to a conventional lawn, rain gardens allow for 30% more water to soak into the ground.
A rain garden is not a water garden. Nor is it a pond or a wetland. Conversely, a rain garden is dry most of the time. It typically holds water only during and following a rainfall event. Because rain gardens will drain within 12-48 hours, they prevent the breeding of mosquitoes.
Every time it rains, water runs off impermeable surfaces, such as roofs or driveways, collecting pollutants such as particles of dirt, fertilizer, chemicals, oil, garbage, and bacteria along the way. The pollutant-laden water enters storm drains untreated and flows directly to nearby streams and ponds. The US EPA estimates that pollutants carried by rainwater runoff account for 70% of all water pollution.
Rain gardens collect rainwater runoff, allowing the water to be filtered by vegetation and percolate into the soil recharging groundwater aquifers. These processes filter out pollutants.
In the design of a rain garden, typically six to twelve inches of soil is removed and altered with tillage, compost and sand to increase water infiltration. The type of alteration to the soil depends on the current soil type, so it is a good idea to obtain a soil test.
Rain gardens are generally constructed on the downside of a slope on your property and collect rainwater runoff from the lawn, roof and/or the driveway. Once water collects in the rain garden, infiltration may take up to 48 hours after a major rainfall. Also, rain gardens incorporate native vegetation; therefore, no fertilizer is needed and after the first year, maintenance is usually minimal.
Rain Garden:-
- Improves water quality by filtering out pollutants
- Aesthetically pleasing
- Preserves native vegetation
- Provides localized stormwater and flood control
- Attracts beneficial birds, butterflies and insects
- Easy to maintain after establishment
As a rule, native vegetation should be incorporated into a rain garden. Native plants don’t require fertilizer, have good root systems, and are better at utilizing the water and nutrients available in their native soils than non-native species. Perennials, shrubs, wildflowers, or a mixture of all three can be planted. Check with your local nursery for a list of rain garden approved plants for your hardiness zone, or search the rain garden plant database.
Rain garden concept is traditional concept and is in practice in hilly areas more commonly for soil water erosion checking and main focus to reduce runoff with more percolation in the soil. Home gardens in many tropical areas act as rain garden as they comprised of many native species in different spatial and temporal arrangement with vertical stratification to slow down the rain speed and beneath slow down the runoff..
Some information related to Rain Garden is shared here
clearchoicescleanwater.org/uploads/88/docs/6038raingarden_FAQs.pdf
https://dnr.wi.gov/topic/stormwater/documents/rgmanual.pdf
www.harpethconservancy.org/make-a.../PattyGhertnersRaingardenguide12109.pdf
www.faribaultcountyswcd.com/FileLib/Rain%20Garden%20Design%20Templates.pdf
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