SAND MINING REHAB. GUIDELINES Combatting The Effects of Sand Mining 12 FEBRUARY 2014 DUCT 4 Edmond Place, Campsdrift, 3201 Sand Mining Rehab Guidelines/Proposal Executive summary The relationship between man and the resources that water courses possess can be described as one sided, with human beings being accused of over exploiting river resources solely for their own ends. Often one forgets that a river has a tendency to continually evolve (naturally), together with the flora and fauna of the adjacent land. But this evolution is hastened due to human activities such as sand mining (unnatural). As population increased and industry developed the relationship between man and the river strengthened since communication routes were required for trade and social exchange. Today it is becoming increasingly difficult to ignore problems associated with flooding of low lying areas which is further exacerbated by sand-mining activities. Whilst safeguarding our infrastructure on the one hand we must remember that a natural water course is a living entity in continual development that should be protected as far as possible. Introduction Sand mining is a problem that could be labelled as one of the more serious environmental problems that South Africa faces. The production and rehabilitation of fertile top sand/soil that will support good plant growth and prevent soil erosion is an extremely slow process. Natural rehab of mined land takes between 12 to 40 years. Loss of sand due to mining is estimated at 0.7 ton per hectare per year. Sand mining subsequently leads to a hastened soil erosion process. This is further worsened by the subsequent heavy rains. Poor mining practices and the mechanical exposure of the sand are the most important causes of soil erosion. The importance of plants in the rehab process and the prevention of soil erosion can’t be over emphasized. This proposal is solely interested in the protection and mitigation of river ecosystems from sand mining.it illustrates the compatibility of incorporating environmentally sound concepts into the design of making/engineering solutions for rehabilitation. This proposal gives a brief background of soil protection and ecological systems and techniques, which may be adopted for greening disturbed areas. This document discusses specific remedies and 1 looks at erosion as it pertains to sand mining practices and the problems caused by erosion. Proper remedies will have to be planned and implemented by experts. Purpose The purpose of this proposal is to highlight the need for the control of degradation/erosion in sand mining sites and to introduce alternative methods for the prevention of erosion. With sand mining practices, water from the adjacent river/stream gives the potential to maim, damage and destroy the river ecology if not managed and rehabilitated correctly. This proposal highlights the protection and stabilisation of river banks which reduces the erosion of slopes. This further protects surrounding human settlements from impact floods. Sand mining sites concerned All sand mining sites concerned are found within the foothill and valley regions of the river/water course. Foothill region- this is the region where the river flows from mountains and into the valley, a sharp reduction in river gradients occur here which has resulted in the deposition of the larger material. The river beds are generally unstable. They are characterised by wide sections and are not cut-in too deeply as the river is wide. Any widening of the channel increases the channel movement which becomes very harmful and dangerous during severe floods. In the foothill regions the presence of solid materials contributes to the stabilisation of the river bed which is constantly compromised by mining activities. Valley regions- a shallow channel is found in this region which forms a sinuous shape which can assume various patterns Straight and sinuous beds Meandering beds Multi-channel beds These flat reaches within the valley region require course correction and back protection. This and other rehabilitation measures require careful planning and can’t be generalised. Each affected site must be analysed individually in a way appropriate to that mined site on the river bank. 2 River habitat and morphology When looking at the restoration and rehabilitation of the mine affected river habitat, one should not only choose what materials are to be used, but also the proper design methodologies. The environmental biodiversity of the river course needs to be maintained thus its morphological diversity is retained. With this type of rehabilitation there can be gradual creation of habitats for the distribution of vegetation and fauna. The bankside vegetation consisting of emergent plants, shrubs and trees plays a significant part in stemming erosion of the valuable soil and habitats even during oncoming flood conditions. The threat of soil erosion/land degradation in the mining sites In the first case, unrehabilitated mined land in the vicinity of the stream threatens the structural integrity and channel of the adjacent water course. Failure to remedy the situation may lead to an expanded river channel. Secondly, erosion on the river banks of the uMgeni may not threaten the river directly or initially, but will have a negative cumulative impact further downstream. 3 Thirdly, the causing of erosion is a contravention of the conservation of agricultural resources act. Soil erosion of the site During sand mining activities, the impacts of vegetation clearing and the formation of access routes to sites for large vehicles has probably the most profound effect on erosion/land degradation The stabilization of soils, particularly in the vicinity of the watercourse, requires special attention. The impact of sand mining activities during the excavation cycle of the plot/site is relatively high as patrols and compliance monitoring on the site are sparsely carried out Proposed solutions to combat soil erosion in sand mined sites Since there is an understanding of the cause of the erosion/degradation which is as a result of the alteration of the drainage/flow pattern of the river channel by the mining of the sand and other interventions. Under these conditions the vegetation is reduced or even destroyed and the velocity and quantity of runoff and stream flow is increased, with the resulting increase in erosion. Where highly erodible soils occur, the effect/impact is more severe. The main objectives in the planning of rehabilitation measures to be taken begins with slope stabilisation. With biodegradable erosion control blankets. The correct placing of these structures will be based on various aspects such as the volume of water passing through, soil/sand type and the slope of the terrain which should be carried out by a specialist. Preventing erosion/degradation caused by access roads Roads are built to provide access for the removal of the sand as well as to provide access for inspection and maintenance. Roads are one of the major causes of soil erosion and land degradation. Research tells us that roads should be planned according to principles of water runoff and should be positioned on a watershed or ridge. Due to the sand being highly sensitive there have been changes to many access routes. Degradation is further exacerbated by the steep slopes of the access routes (slopes should not exceed 7%) 4 Areas that have erodible soils/sands as well as areas in the vicinity of watercourses require special measures Erosion/degradation prevention structures These structures or systems are to be used in eroded/disturbed areas and aim to halt active erosion and re-establish vegetation Three categories of solutions are suggested. They are: Heavy systems: these solutions include concrete or brick structures and gabions and reno mattresses etc. concrete or cement structures can be constructed on solid rock foundation. Care should be taken not to disturb the environment where rocks are collected as this could result in the creation of new erosion problems. These structures are normally expensive and should be planned carefully by a specialist Light systems: these systems include silk screens, erosion control blankets, turf reinforcement mats and geocells.The re-establishment of vegetation is encouraged by using soil reclamation rolls, eco logs or seeded coir mats, also referred to as small structures Soil bioengineering techniques: this refers to the use of a variety of plant species without any inert(artificial) materials Small structures Recently the use of “small structures” has been suggested to combat the type of soil erosion/land degradation typically found in sand mining sites. These structures can be erected with minimal labour and at a low cost and have been shown to be effective in the re-establishment of vegetation in disturbed areas. As previously mentioned, these structures are cheap to construct and the materials used will not pollute the environment. Soil reclamation rolls With sand mining, most of the topsoil has been removed and vegetation also becomes absent. Water penetration is low and runoff is high. The rehabilitation of vegetation is normally achieved by the removal of animals, human activity, the ploughing and planting of vegetation. The success of these measures is also highly dependent on sufficient rainfall. 5 The remedies which involve the re-establishment of vegetation will necessitate the co-operation of the concerned affected stakeholders. Where possible, areas under rehabilitation should be fenced off but this is often not practical for sand mined sites. It is therefore vitally important for the successful rehabilitation of a mined site to involve the miner in solving the problem. In many cases, the miners have the means to implement some of the remedies suggested above, with their own equipment and labour. This work may be carried out during slack times and in this way contribute to sustainable job creation in the rural areas. This approach is also certain to reduce any complaints about work. The contractor/miner will have a stake in ensuring success of the project Guidance to solutions that combine various practices and ecological principles Soil/sand protection Purpose of soil protection/rehab- vegetation is an excellent defence mechanism which nature has produced to protect soil against erosion.Sometimes,however erosive forces are too large or vegetation needs to be developed under difficult conditions and nature needs a helping hand with erosion control. In such analysis inert materials can be brought into the solution. Vegetation improves the stability of the subsoil against erosion and deterioration of the riverbank. Rehabilitated areas improve the water quality, habitat and aesthetic appeal of the river channel. Vegetation Plant roots function as soil reinforcing agents. This further reduces slope instability and erosion due to vegetation’s capability of increasing surface roughness flow of rainfall and water is retained and seepage is reduced. As previously mentioned, plants provide immediate river habitat improvements. Biodiversity and habitat value are increased as vegetative growth increase and natural succession occurs. 6 Benefits and features of soil protection/rehabilitation Benefit Feature Cost effective A combination of solutions whether it be soil engineering or vegetation of structural solution Minor site Rehab techniques generally require minimal access for equipment and disturbance during workers, and cause relatively minor site disturbance during installation installation works Techniques are Useful on even the most sensitive/steep site where machinery is not useful on almost any feasible site Appropriate for These practices are appropriate for environmentally and aesthetically environmentally and sensitive areas such as rivers. aesthetically sensitive areas Immediate These rehab. Systems can be designed to withstand heavy events after protection installation/implementation Strong initially and Rehab. Systems are strong initially and grow stronger with time as the grows stronger with vegetation becomes established time. Erosion control The vegetation traps sediment, which further promotes growth and erosion control Natural plant Enhances conditions for the natural colonisation and establishment of colonisation plants from surrounding plant community Increase in soil Dries excessively wet sites through transpiration as the vegetation grows quality by reducing soil moisture Increase in soil Reinforces soil as roots develop adding resistance to the sliding and stability to plant displacement of slopes growth Soil temperature Plants provide protection from the extremes of heat and cold, which lead moderation to a healthier environment for the plant germination and growth Improves water Heavily vegetated banks filter and slow storm water runoff and trap quality sediment, thereby improving water quality 7 Air quality The removal of dust offer air quality improvement and increased oxygen improvement production Low maintenance Rehabilitated sites become self-maintaining and self-repairing Jobs Implementing rehab. Systems is often labour intensive, due to difficult access to sites and hand planting requirements for vegetation Environmental Supports indigenous plant species and wildlife habitat and speeds up benefits ecological succession Positive impact on Vegetation provides: wildlife Shelter and nesting sites protection from predators and floods Shade-keeping the water cooler in summer and slowing the growth of algae Aesthetics A source of food Rehab measures support plant species and wildlife habitats which improve the aesthetic appeal of the river bank and channel Improved biological The growth of the vegetation tend to improve the biological conditions conditions thereby restoring the natural ecosystem Rehab systems will use biological, mechanical and ecological concepts to control erosion while preserving ecological value. It will rely on various tools such as living plants, traditional construction material to stabilize the soil and to provide good wildlife and fisheries habitat in riparian systems. Rehab. Considerations Cost: the project/s will need to fulfil all the functional requirements while staying within budget for both construction and maintenance. Safety: considerations must be given to eliminating potential risks to the labour force and the public. All factors relating to safety should be incorporated, including consideration of all possible activities that may take place on and around the site, whether authorised or not. Maintenance: rehab. Should allow for maintenance including the repair of any damages. Durability: the rehab. Should remain effective for the duration of the river life at least Flexibility: the ability to absorb any deformations without impairment of its original shape/function. 8 Stability: the rehab. Structure must be capable of supporting the riverbanks, stabilising the underlying soil and preventing soil erosion Factors involved in the rehab. Process Soil/sand: when establishing plants for rehab the soil must be consolidated which allows root growth to thrive in the site. The features of topsoil that are significant to successful plant growth and therefore rehabilitation are: Air in the soil profile is important as roots derive air for biochemical activity from the soil and not from the leaves. Aerated soils regulate the soil temperature, making it suitable for plant growth. Moisture retained by humus is constantly available to be drawn by the root system while plants are growing Nutrients are maintained in the humus and are available over an extended period “The quality of soil/sand will directly determine the growth of surface vegetation” Vegetation It is recommended to consult a local plant specialist when determining which vegetation to use for a rehab. Project. Root contribution to soil stability The most obvious way in which vegetation stabilises soils is by root reinforcement. The intermingled roots of the plants bind the soil to slope and increases resistance to sliding. Roots: deep roots penetrate the subsoil for anchorage It has a positive effect on soil moisture depletion and interception, thus increasing soil strength by mitigating or delaying the onset of saturated conditions in the soil. Trees together with grasses and shrubs have been used to control erosion on slopes and to stabilise landslides for many years. The vegetation has a net stabilising effect on most slopes 9 Effects of vegetation on slope stability Mechanism effect Hydrological 1 Foliage intercepts rainfall, causing absorptive and evaporative losses that reduce ↑ rainfall for infiltration 2 Roots and stems increase the roughness of the ground surface and the permeability ↓ of the soil, leading to increased infiltration capacity. 3 Roots extract moisture from the soil, which is lost to the atmosphere via ↑ transpirtation,leading to lower pore-water pressure 4 Depletion of soil moisture may accentuate desiccation cracking in the soil, resulting ↓ in higher infiltration capacity Mechanical 5 Roots reinforce the soil, increasing soil shear strength ↑ 6 Tree roots may anchor into firm strata, providing support to the upslope soil mantle ↑ through buttressing and arching 7 Weight of trees surcharge the slope, increasing normal and downhill force ↑↓ components 8 Vegetation exposed to the wind transmits dynamic forces via the tree stem into the ↓ slope. 9 Roots bind the soil particles at the ground surface, reducing their susceptibility to ↑ erosion. ↑ Beneficial to stability ↓ Adverse to stability Plant selection for rehab. The success of rehab. Solutions is greatly dependent on plant stem density and length, root penetration, rooting habits, uniformity of vegetation, soil erodability and the physical and chemical characteristics of the remaining soil/sand. 10 There are five biological factors for plant growth and rehab. 1. Temperature 2. Moisture 3. Nutrients 4. Oxygen 5. Light Choosing the most appropriate solution for rehab. Requires consideration of a no. of factors. Plants chosen need to be able to establish easily, thus they become fast growing and give immediate protection. These plant species usually require a great deal of nutrients so growth in most cases is slow to take off. Another important consideration is what the end function of the chosen plant will be .Various plants have differing characteristics, from the strength of their root systems to whether they provide good ground cover. Inspection and maintenance Regular inspection and maintenance of installed rehab. Practices should be conducted, particularly during the first year. Prompt correction of any fault is essential to prevent major problems from developing. Plant establishment is most critical in the success of the rehab. Adequate watering requirements must be met at this stage of the plant life cycle. Care must be taken not to over-water the sites, as this could lead to failure of rehab. Due to slope instability. Plants should be monitored for four to five weeks after rehab. To ensure the success and survival of the plants The plants roots need to be covered and kept moist All plants should be checked periodically or after storms to ensure they remain properly secured. Make necessary repairs promptly 11 Conclusion Vegetation can make better many of the factors and conditions causing earth slope and river instability. Rehab measures must be suitable for the life of animals and plant communities thus a full restoration of our natural ecosystem can take place 12 REFERENCES Maccaferri SA (Pty) Ltd MAC.R.A 1 – Bank Protection Reference Manual. Agostini, R., Cesario, L., Ferraiolo, F., Papetti, A., 1988. Flexible gabion and Reno mattress structures in river and stream training works, Section two: Longitudinal structures, Officine Maccaferri S.p.A. – Bologna, Italy. ASTM, 2000. Standard Practice for Construction of Live Fascines on Slopes, Draft No. 2, April 4 2000. Ciarla, M., Ferraiolo, F. and Malcevschi, S., 1995. New Design Criteria Respectful of the Needs of the Environment, XXVI International Erosion Control Association Conference, March 1993, Atlanta, Georgia, USA. Chow, V.T., 1959. Open Channel Hydraulics, McGraw – Hill Book Co., New York, Toronto, London. Di Pietro, P. and Brunet, G., 2000. Design Considerations Related to the Performance of Erosion Control Products Combined with Soil Bioengineering Techniques. ASTM Workshop: Testing and Performance of Flexible Erosion Control Materials. Di Pietro, P., 2000. Soil Bioengineering and Ecological Systems: Erosion problems in natural and altered habitats can be controlled through the use of geosynthetics. In: Geotechnical Fabrics Report, September 2000, Volume 18. Number 7. Di Pietro, P. and Scotto, M., 1999. Grids And Steel Mesh Combine For Cost Savings, GFR, September 1999, Volume 17, P 34-38. DWAF, 1998. Department of Water Affairs and Forestry. Soil and Water Conservation: An Audit of South African Approaches and Activities, Learning from South African Experience in Sustainable Land Management. Ellis, H., 2001. Natural Progression. In: Soil Bioengineering: Integrating Ecology with Engineering Practice, Ground Engineering, March 2001. Environment Agency, undated. Understanding Riverbank Erosion: An Information Booklet. Escarameia, M., 2001. The Right Choice for Erosion. In: Soil Bioengineering: Integrating Ecology with Engineering Practice, Ground Engineering, March 2001. Fischenich, J.C., 1997. Hydraulic Impacts of Riparian Vegetation – Summary of literature U.S. Army of engineers – W.E.S. Ferraiolo, F, 1999. Application of Inert Materials in Bioengineering, Officine Maccaferri SpA, Bologna (Italy). In: Proceedings of the First Conference on Groundwater bioengineering for Erosion Control and Slope Stabilization, April 1999, Manila, The Philippines. 13 Greenway, D.R., 1987. Vegetation and slope stability pp187-230 In: Anderson, M G, Richards, K S (Eds) Slope stability Chichester, Wiley. Greenwood, J., 2001. Rooting for Research. In: Soil Bioengineering: Integrating Ecology with Engineering Practice, Ground Engineering, March 2001. Maccaferri, 2000. Designs On The Market, Soil Nailing and Reinforced Soil. Ground Engineering, February 2000. 14 APPENDICES Photos of erosion control implements: 15 16 17