The next part of the project will involve installing a pool at the top of the catchment area to slow incoming water and direct it south along the swale along the road and west downhill into the flower bed. Both areas are lined with drainrock and then larger tumbled round rock will be laid in on top. For the catchment pool we had to pull out one of the cotoneaster shrubs, remove the stump and then back fill with soil and drainrock.
Work by volunteers and interns continues on two projects in the garden. Soil/road base from the rain garden/french drain project has been dug out and replaced with rocks collected in the garden to capture and slow rain water to flow through into the garden beds on the slope above the lawn. Meanwhile the displaced road base is sent to the new redwood steps project in the Redwood grove to back fill the new hand hewn redwood stair risers.
We are in a drought we have been thinking of any or all ways to capture and conserve water for the garden. We intend to redirect water that flows down the driveway during a rain storm into the flower bed. In order to this and not wash out the flower bed we will construct a french drain/rain garden 1 to 2 feet deep, 2 feet wide and about 30 feet long along the road and at the top of the slope. We will redirect the runoff with sand bags into the swale lined with tumbled stones that we dug up in another part of the garden. Most french drains are constructed of stones with a perforated pipe at the bottom of the swale to redirect water somewhere. Most rain gardens are held in place by plants to filter the water. Our design will be borrowing from these two ideas. Our swale will run perpendicular to the slope and water will perk slowly through the permeable subsurface down the slope to the lawn. We have begun the project with a U.C. Berkeley Landscape Architecture undergrad student, volunteers and our interns from Albany High School EDSET program.
Within the last few days we have gotten over 5 inches of rain. A tributary of Cerrito creek runs through the garden and is impacted by urban runoff. The video is of water blasting through the garden after a big down pour on Sunday morning. We recently repaired the base of the waterfall with volunteers from St. Mary's High School along with our staff, volunteers and EDSET interns from Albany High school. The repair seems to be holding up and was done just in the nick of time.
We have been collecting rainfall data since 1965 here in the garden. Rain year begins July 1st and ends June 30th. We are looking forward to this years rain. Download xlsx file: Blake Garden Rainfall Data 1965-2012 xls file
Our 20ft waterfall on the south side of the garden is part of a tributary to Cerrito creek. Over the past several years, the 1970's era creek restoration project has been worn by the drilling forces of the winter rains. The water comes into the garden with such force that it channelizes, undercuts and washes out areas of the creek. This year we had no choice but to fix the waterfall in fear that it would collapse if we got a big rainstorm. Freshmen from St Mary's High School along with their teacher Jeff assisted staff and Blake Garden volunteers to re-stack the base of the waterfall with 80 lb. bags of concrete. Some students ziplined bags of concrete to others waiting below, who stacked and spiked it into place with steel rebar. Above the waterfall, others were taking out excess gravel that had washed down from above, and moved it to regrade the path of the nearby wetland and new grassland. Weeds from the creek bed were added to compost piles that will be used in the future to boost the soil quality of new planting beds for native grasses. Our two EDSET interns, Karl and Michala, from Albany High School assisted with the project. [nggallery id=183]
We continue to develop the wetland and the hillside above. The hillside was planted with Acacia baileyana to prevent erosion. Because it is invasive if allowed to flower and go to seed, we decided to shrub it and replace it gradually with native grasses and succulents that are also good for erosion control. By cutting it back hard periodically it provided us with some interesting material to replace an aging bamboo and twine fence that we put around the perimeter of the wetland to protect newly planted native wetland species. Volunteers and students stripped the acacia branches, developed some mock ups for the fence design and are installing the the branches around the wetland. The branches are tied together with bark stripped from the branches and then soaked in water to become more pliable. This is another example of regenerative design that we use in the garden.
Blake Garden has been keeping rainfall records since 1965. This year we have measured some late and heavy rains at the garden. Whereas 2 months ago it seemed bleak, now our measured totals for the year have topped 27.78 inches, which exceeds the mean measurement of 26.25 inches. Drought still remains a concern for California though, as the Sierra snowpack for March 2012 was way below normal. Take a look at The State of the Climate maps of the USA at http://www.ncdc.noaa.gov/sotc/drought/ for further information about drought nationwide. Links to 2012 Blake rainfall pdf & xls files : Blake Garden Rainfall Chart 1965-2012 pdf file Blake Garden Rainfall Averages 1965-2012 pdf file
Phase one of the creek restoration project has started. We are covering the steep banks with jute mesh and securing it with redwood branches and stone pine stakes: debris recycled/reused from the garden. This process will help with erosion control. Next we will be planting riparian plant species on the hillside. The concept is that when these water loving species drop their roots into the ground they will hold the soil on the bank while simultaneously natural materials will rot.
Albany High School EDSET interns Jamie, Xian and Sareena finished their Fall semester at Blake Garden last week. They helped to hook up the cistern in the Australian Hollow to the seep via a bamboo aqueduct. The water from the seep will be used to water the new grassland planting. Water flow rates into the cistern were measured at 12 minutes for 1 gallon. The capacity of the cistern is 1400 gallons. At the current flow rate this means that the cistern will fill to capacity in 11.5 days.