Objects/shapes/ physical projects > On the ground > system for erosion control “vegetation engineering systems for slope erosion control” STRONG SLOPE REVEGETATION (Steeper than 2:1) I/ General description and characterization of the NBS entity I.1 Definition and different variants existing Definition • Stabilizing soils structure on steepened slopes through revegetation in order to minimize or prevent the erosion of soil by wind or rain and landslides, avoiding sedimentation problems Smart slope-vegetated-retaining-wall, Dakota. Furbish 2013. © United Themes. When the slope is really steeped, the most common slope stabilization and erosion prevention method is some kind of retaining slopes method joined with revegetation. The origin of unstable slopes can be natural because of the soil geotechnical properties, or as consequence of human activities that create new cutting slopes or embankments during construction works. When soil is disturbed at a construction site, or the natural vegetation cover is retired, the erosion rate may increase significantly. Proper planning and use of erosion control prevention and mitigation measures can reduce the impact of human-caused erosion. In order to stabilize steepened slopes, some kind of soil retention method is nevertheless needed; joining it with a well-established vegetative cover is one of the most effective methods of reducing erosion in unstable slopes steeper than 2H:1V. The retention method keeps the soil meanwhile vegetation protects soil surfaces from rain generated splash erosion and can help to slow runoff flows across a disturbed ground. 1 / 11 In addition, plant roots hold their soil in place, keeping it from washing away during rainstorms. Lastly, trees help to prevent high winds from blowing away top soil because the trees provide windbreaks, which can prevent high winds. Vegetation should be established on the slopes as soon as possible when the construction works are finished. In the urban environment, even though mud, dirt and sand are natural they are still serious pollutants that must be prevented from entering the waterways, including the storm water drainage systems, which discharge to creeks, waterways, rivers and beaches. There are two main variants for the stabilization of steeped slopes and its revegetation: - Reinforced soil slopes (RSS) with cellular confinement systems (CCS) - Mechanically Stabilized Earth Wall (MSE): o Multilayer geocell o Concrete blocks o Gabions In general, MSE walls are distinguished from reinforced soil slopes (RSS) by the inclination of the facing: • Reinforced soil slopes are inclined flatter than 70 degrees from horizontal. • MSE walls are inclined steeper than 70 degrees from horizontal. (7. TAC 2017) Multilayer geocell earths retention wall schema © Geoweb Different variants existing =>. Reinforced soil slopes with cellular confinement systems (CCS) (also known as geocells) and revegetation Vegetated geocell for slope protection Geocell is a honeycombing interconnected cellular confinement system. It is made out of high-strength polyethylene or other plastic, and can be green in and of itself. Some geocell is made from recycled plastic and is recyclable again at the end of its useful life. “It has been observed that ‘Geocells’ significantly enhances the load-bearing capacity of soils and reduces settlement of the concern geotechnical structure”. (1) This geocellular containment system provides a cost effective solution for the reinforcement of cuttings and embankments, preventing slope failure and soil loss. - 3D structure reinforces the upper soil layer and resists erosive conditions and sliding forces beyond limits of other systems. Long-term solution for sustainable vegetation, permeable aggregate or geomembrane protection. - Reduces land space requirements and costs by allowing slopes to be designed steeper than when unconfined. Each open cell is also permeated with slots, to allow quick threading of root tendrils. The lifespan of CCS in slope protection applications is less critical as vegetative growth and root interlock stabilize the soil. This in 2 / 11 effect compensates for any long-term loss of confinement in the CCS. Sections of geocell are shipped flat. When you pull open a panel and reveal its 3-D structure, it looks something like a honeycomb. Once the geocell installed, their cells are filled with soil. When the wall is all covered it’s finally hydroseeded or revegetated. “The use of Geocell for erosion control applications eliminates complicated and expensive construction techniques. Geocells 3D structure provides a blanket of 'cells' on the slope surface which can be in-filled with a variety of materials depending on the application, This improves resistance to erosive forces such as rainwater run-off on steep or unstable slopes” (2). Geocells folded up for transportation and storage A slope covered with geocell and infilled with topsoil © Henfengsuye © Terram geosynthetics A slope covered with geocell The same slope once vegetation has grown © Alpha Pinnacle © Alpha Pinnacle => Mechanically Stabilized Earth Wall (MSEW) (earth retention), or Vegetated retaining wall. MSEW stabilizes unstable slopes and retains the soil on steep slopes. The wall face is often of precast, segmental blocks, panels or geocells that can tolerate some differential movements. The walls are infilled with granular soil, with or without reinforcement, while retaining the backfill soil. They serve a vital purpose in construction and erosion control, bearing loads and holding slopes back from sliding down, but sometimes they are not the nicest things to look at. Nevertheless, vegetated retaining walls fulfil their primary load bearing or erosion-prevention purpose, but with an extra, environmentally beneficial aesthetics. Reinforced walls utilize horizontal layers typically of cell walls, articulate concrete walls or gabions. The reinforced soil mass, along with the facing, forms the wall. In many types of MSE’s, each precast row provides individual cells that can be infilled with topsoil and planted with vegetation to create a green wall. § Cell walls Cells walls check the runoff streams associated with rainfall, keeping the overall system intact. The infill material also rests within individual cells, allowing for much higher angles of Cells grid filled with soil 3 / 11 promotes vegetation as both another source of reinforcement and natural aesthetics. Overall effectiveness of the system is increased with the plant roots integrated into the grid system. Geocells are manufactured in different deeps and cell sizes. One of its advantages is that it is easily installed without specialized equipment or crews. Stabilizing Forces: Interlocking cells provide tension and Increased friction surface between layers creates resistance Forces’ stabilization between Geocells Multilayer geocell slope retention system © JANELLE KATHRYN.P.ONG. © GEOWEB Walls with Natural Vegetation Geocell wall construction’s schema © GEOWEB © Aldi Helme Egland UNDERyourfeet § Articulated Concrete blocks The retaining wall face is built interlocking cast blocks used as a face wall connected to mechanical reinforcement (metal smooth or ribbed steel bars or geosynthetic fabric; linear, grids or mats etc.). Concrete can be vegetated. Several manufacturers make cast concrete blocks with pockets that can be filled with growth media. Then pockets are planted. The entire face of the wall will be covered with vegetation upon grow out. 4 / 11 Articulated concrete wall Vegetated concrete wall © Furbish.co © Simpson Gumpertz & Heger Soil erosion and hydroseeding (soilerosiononline.com) § Gabions A gabion is usually a cage, cylinder, or box filled with rocks, concrete, sometimes sand and soil for use in civil engineering, road building, military applications and landscaping. Gabions became very popular because they can be stacked vertically and they look like more natural than concrete blocks. Vegetated gabions still fulfil their primary load bearing or erosion-prevention purpose, but with an extra, environmentally beneficial flourish, “On the top, it can be planted jasmine or any other type of vining plant. The vines will eventually drape over the wall and weave in and out of these crab traps (gabions). The mesh (openings) is about the same size as those found in chain link fencing, perfect for ‘weaving’ plants.” Advantage of gabion baskets: - Their porosity. If there is one thing that’s the enemy of retaining walls, it is water. Gabions filled with broken or crushed stone have built-in drainage. - Their flexibility. Subjected to alternating forces of tension and compression, the inherent flexibility of a gabion structure enables it to deform rather than break. 5 / 11 © Fengxiang Hardware Limited © Dong Xue I.2 Urban challenges and sub-challenges related + impacts Main 02| Urban water management and quality - Avoiding storm water system drainage challenges and > 02-1 Urban water management problems due to the accumulation of sub-challenges 04| Biodiversity and urban space eroded sediments, targeted by the > 04-1 Biodiversity - Vegetated slopes promote vegetation NBS > 04-2 Urban space development and growth, provide habitat for insects and regeneration animals and in consequence biodiversity > 04-3 Urban space management - Avoiding soil erosion and problems with 05| Soil management slope stability and sediments dispersion > 05-1 | soil management and quality - A well-stabilized slope avoids the risk of 10| People security landslides and the damage to people and > 10.2 | Control