QuestionI manage a community in Pinellas County, Florida (Tampa Bay Region). It has 2-story condo buildings. When it rains, water cascades off of the roof causing the ground in the plant beds to erode. Gutters are not feasible due to the architectural design. People have suggested installing either 1" river rock or crushed sea shells. What do you recommend?
Answer
Rain caused erosion
Hello Allen:
Good question about rainwater and water falling from your roof. Without gutters or downspouts this will always be a problem. If you have no way to install gutters of any kind then you need to create a splash zone free from soil or dirt. The dirt as you well know will splash onto adjacent plants and walls and can cause a real maintenance issue and even damage and kill small plants. I come across this frequently. For the record, I advise anyone considering this issue to install gutters and pipe them, if possible, to a rain garden or cistern.
However when this is not possible I would suggest using gravel that is complimentary to your landscape. 1" is good because it is too big to be moved by average rain drops or rainfall. Peagravel (Pea gravel) can be splashed out of place and become a mess, plus its harder to walk in soft small round gravel as it moves under foot. Also I prefer rounded river gravel or river rock for this application because it tends to absorb the splashes unlike fractured quarry gravel such as slate or marble chips which tend to splash more. I would recommend that you excavate a trench 12-18inches minimum wide and 6 inches deep. Lay filter fabric, silt fence, landscape fabric or weed screen (or weed control fabric) in the bottom and then cover with gravel. Do not use plastic as it will hold water. Trim off the excess landscape fabric around the edges and mulch up to the edges of the gravel. Make sure you place enough gravel and stones so that the surface of the gravel is equal to or higher than the surrounding mulched landscape beds. Your done. Not however if your soil is not sandy and quick to percolate and absorb the water, you may want to install a french drain in the trench to route water away from the house. This is especially true for folks with basements or crawl spaces that are damp and or flood periodically. Keep in mind if you install a french drain the trench will need to be deeper. Search my previous answers for french drain construction.
One final comment. When selecting the gravel, be sure to select a color that is not going to be glaring or bright. You can even get lava rock (lavarock, lava-rock) and river rock (river-rock) that is similar in color to mulch including hardwood mulch, pine nuggets, cedar and pinestraw. These colors will blend in well with the natural surroundings.
Allen I hope you find this information uesefull. Be sure to check out my new website if you like at http://www.seanjmurphy.com
Also if you like to go camping, I am spreading the word about a new site that is coming on line soon for which I will be blogging, that will feature campground user ratings, reviews, and maps in addition to articles on camping. It will be up and running in early 2011 at http://www.netcamper.com please stop by and book mark us now so you can come back in a month and check it out.
Best of Luck with your DIY landscape proeject.
Sean J Murphy, ASLA, ISA, LEED AP
www.seanjmurphy.com
www.netcamper.com
