Tyler Ludens wrote:How to you envision using the rocks?
Tyler Ludens wrote:Rocks that small can't be stacked, so they are going to tend to spread out to achieve the "angle of repose" which will make them spill off the edge of the terrace and/or take up most of the space you might want for improved soil.
Forgive me, I thought logs were a good way to start these walls. Can you tell me what you would prefer the wall be made out of? Regarding logs, not only did I plan to use them in the wall itself, but with so many logs around my property I wanted to use them as part of my filler material to eventually decompose. My hope is it would act as a hugelculture while I wait for it to turn into the soil.
Tyler Ludens wrote: Personally I would not use small rocks or logs in a terrace wall. I think it would be asking for collapse.
Rene Nijstad wrote:I agree with Tyler, I don't think you can make anything stable out of such little rocks.
Rene Nijstad wrote: That said, what is your soil like (sand, clay)? How steep is the slope you want to terrace? How big and high are the terraces? From your description it sounds like probably 3 feet high or less?
Rene Nijstad wrote: We have heavy clay soils and our terraces are pretty stable by themselves. If you can make sure that excess rainfall flows to the back of the terraces (instead of over the edge) and has a controlled way to exit the terraces, risks of collapse can be made very small.
Seth Marshall wrote:Forgive me, I thought logs were a good way to start these walls. Can you tell me what you would prefer the wall be made out of? Regarding logs, not only did I plan to use them in the wall itself, but with so many logs around my property I wanted to use them as part of my filler material to eventually decompose. My hope is it would act as a hugelculture while I wait for it to turn into the soil.
John C Daley wrote:If you created gabions with wire mesh and filled those with the pebbles you may be able to create terraces which will last a long time.
Why did you purchase the block, knowing this work was needed?
"Farmers described a process in which green and dry brush is cut and piled in mountain drainages in a cross-channel direction to retain soil and sediments washed down from the hills during the rainy season. Called bordos, these brush barriers are lined in the front with stones found nearby to create a permeable retention wall. The stones are carefully fitted like a jigsaw puzzle, but they are not cut or bound with mortar. The placement of stones is progressive and begins after the brush bordos have already begun to collect sediment. Low, vertical rows of stone are positioned in front of the brush bordos to create the base of a terrace wall. As the rains continue to transport more sediment, additional stone rows are placed slightly upslope and at a tilt, increasing terrace height. The result is a sloping, porous wall that allows excess water to filter through. This mode of construction protects crops from oversaturation and prevents wall collapse, since strong currents of water are filtered through the walls. Terrace maintenance is a continuous, yearly process."
"The contemporary model of bordo terrace construction corresponds well with the stratigraphic profiles of Prehispanic terraces exposed in erosion cuts around Cerro Jazmın and in the lama-bordo terraces excavated at the sites of Yucundaa and Nicayuju (Perez Rodrıguez 2006, 2014; Perez Rodrıguez et al. 2011). At these sites, the initial stage of the terrace wall consisted of a trapezoidal pile of uncut stone (Figure 3). These piles were up to 50 centimeters wide and had no mortar, and were similar in shape to the brush barriers (bordos) described in the ethnographic interviews. The barriers exposed by the excavations were then topped by narrower terrace walls of one- or two-stone rows. Based on the stratigraphy preserved behind terrace walls, subsequent rows were added as the sediments accumulated during rainfall events."
John C Daley wrote:
Are there many rocks in the area, sometimes they are around road cuttings etc.
Seth Marshall wrote:Hi Beth! That's very interesting and definitely similar to what I'm doing. It was hard to visualize what they meant about placing these stones in front of the green and dry brush. Do you think they meant they placed these stones "on top of and at the front of" the piles of brush? That's the only thing that would make sense to me. I would certainly love to learn more, thanks for sharing this!
John C Daley wrote:I would suggest any timber use is unwise, since they will rot way.
"Farmers report cutting green and dry brush and piling it up in drainages to create barriers that will stop the soils and deposits that wash down naturally from the adjoining hills during the rainy season. From these brush barriers bordos or barriers of soil form. Often, these soil barriers are lined with uncut stone found nearby to create a façade. These stones are carefully fitted together but they are not bound with mortar. Since the soil bordos are the first to form, short and very vertical, single rows of stone are then placed in front to create the base of a terrace wall. As the rains continue to wash down sediment, additional stone rows are placed on top, making the terrace wall grow up and back. The result is a talud or sloped wall. Terrace walls are porous allowing excess water to simply filter out, which prevents crop damage from oversaturation and rotting."
"Lama-bordo stratigraphic profiles show that terrace walls were essentially rock piles of uncut stone with no mortar. Around Cerro Jazmín we identified a number of tall terrace walls that consisted of single rows of stones that could not have been freestanding walls (Fig. 3). These start as a very short and vertical single-row stone wall, about 30 to 50 centimeters tall. This initial wall is at an almost 90° angle from the ground. After this vertical segment, single stone rows were continuously placed as the sediments filled in the terrace and supported the stones. The top rows, however, were no longer vertical but tilted towards the back of the terrace to support the slope created by the terrace sediment as it collected.
"The excavated terraces at Yucundaa and Nicayuju showed a slightly different pattern of construction. The initial stage of the terrace wall consisted of building a trapezoidal pile of uncut stone (Fig. 4). These piles, some up to 50-centimeters wide, perhaps mimic the shape of the brush barriers described in the interviews. The barriers exposed in the profiles of terrace excavations are then topped by narrower terrace walls of one or two stone rows. It appears, based on the stratigraphy retained behind these walls, that these subsequent rows were added as the sediments washed during the rains."
"The narrow Prehispanic terraces have been modified and widened to accommodate draft animals or occasionally tractors. Manure and fertilizers are used to enrich terrace soils and different crops are cultivated, including GMO tomatoes that are grown in elaborate government-subsidized greenhouses."