Your Dam Your Responsibility (PDF~1.2MB)

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7 Operation and Maintenance of Dams 7.5.10 Vegetation (a) Trees Self-sown plants, trees or other deep-rooted plants should not be permitted within 5 metres (or the anticipated height of the mature growth) of the embankment or spillway. The roots of this type of vegetation could provide a path for leakage through the dam and, ultimately, result in its failure. Planting trees and shrubs can provide windbreaks, which prevent wave action and, therefore, soil erosion, and also give shelter for wildlife. If trees are required, they should be planted around the foreshore of the water storage, well away from the dam embankment and spillway. The dominant wind direction needs to be considered. (Refer also to booklet ‘Trees at Work – Improving Your Farm Dam’ from Greening Australia). (b) Total Catchment Area Protection To maintain the required depth and capacity of a farm dam, it is necessary that inflow be reasonably free from sediment. Selective plant use can be used to trap silt and improve water quality. The best protection from sedimentation is to control erosion of the surrounding catchment area. Land with a permanent cover of vegetation, such as trees or grass, makes the most desirable catchment areas. If the catchment area is denuded and eroding, you may need to utilise cultivated areas that are protected by appropriate conservation practices, such as contour tillage, strip-cropping, conservation cropping systems, and other land improvement practices. (c) Weed Control Aquatic weeds in farm dams can block pump and pipe inlets, deter stock from drinking and, in some cases, taint the water. If weeds are treated when they first appear, dams can be kept relatively free of some of the more troublesome species. All plants can become a problem and each may require a different control method. However, in all situations the same factors should be considered in deciding what control methods, if any, should be used. In each case: • determine whether there is a problem and, if so, what it is; • identify the specific plant causing the problem; • find out what control methods are available and which of them could be used; • investigate whether these control measures could cause any other problems (eg. toxicity to fish and livestock) and, if so, whether they can be avoided; and • decide whether or not all factors considered, control is practical, desirable and worthwhile. 7 39
40 7 7 Operation and Maintenance of Dams 7.6 Modifications (a) Spillways Experience has shown that some landowners or lessees try to modify the spillway on a dam to achieve an increase in storage capacity. This practice is fraught with danger. Result of overtopping due to inadequate spillway capacity If you fill in or obstruct a spillway then the chances of overtopping the dam are greatly increased. Water pressure loading on the dam wall will also increase due to the added height of water and this may cause instability in the bank and embankment slips. (b) Crest Modification PHOTO COURTESY OF MELBOURNE WATER Even the addition of topsoil to the top of an existing dam has been tried as a means of gaining an increase in storage capacity. This can create problems because it is not easy to get a good bond between the top of the dam and the new material and topsoil is very permeable. Because of the shape of the dam a simple raising will also result in a narrower crest width making maintenance difficult. Modifications are best left to a suitably qualified engineer to assess and design a safe structure to meet your needs. Otherwise it may be the most expensive water you ever collected.
Page 1 and 2: Irrigation and Commercial Farm Dams
Page 3 and 4: ii Published by the Victorian Gover
Page 5 and 6: iv Contents 6 Safety Surveillance .
Page 8 and 9: 1 Introduction It makes good busine
Page 10 and 11: 2 Risks Posed by Dams 2.1 Owner’s
Page 12 and 13: 2 Risks Posed by Dams The most comm
Page 14 and 15: 2 Risks Posed by Dams 2 Note: The r
Page 16 and 17: 3 Licensing Requirements for Farm D
Page 18 and 19: 3 Licensing Requirements for Farm D
Page 20 and 21: 4 Planning to Build a Dam It is imp
Page 22 and 23: 4 Planning to Build a Dam 4.3 Types
Page 24 and 25: 4 Planning to Build a Dam 4 2. Turk
Page 26 and 27: 4 Planning to Build a Dam becomes a
Page 28 and 29: 4 Planning to Build a Dam 4.6.2 Ext
Page 30 and 31: 5 Construction of a Dam Mixing tops
Page 32 and 33: 5 Construction of a Dam is inviting
Page 34 and 35: 6 Safety Surveillance 6.1 Purpose o
Page 36 and 37: 6 Safety Surveillance QUICK VISUAL
Page 38 and 39: 6 Safety Surveillance 6 Warning: If
Page 40 and 41: 7 Operation and Maintenance of Dams
Page 48 and 49: 8 Dam Failure Emergency Section 8 i
Page 50 and 51: 8 Dam Failure Emergency Action 4. I
Page 52 and 53: 9 Decommissioning of Dams 9 The sit
Page 54 and 55: 10 Glossary of Terms Cut-off An imp
Page 56 and 57: 10 Glossary of Terms Monitoring Rec
Page 58 and 59: Publications directly relevant to f
Page 60 and 61: Appendix A A • probe - a ten-mill
Page 62 and 63: Appendix A Inspection Procedures Ge
Page 64 and 65: Appendix A A and the resistance to
Page 66 and 67: Appendix B 1. Seepage Problem Possi
Page 68 and 69: Appendix B Problem Possible Causes
Page 72 and 73: Appendix B 2. Cracking, Deformation
Page 76 and 77: Appendix B 3. Miscellaneous Problem
Page 78 and 79: Appendix B utlet Works and Concrete
Page 80 and 81: Appendix C The depth of the core tr
Page 82 and 83: Appendix C will be needed. In stabl
Page 84 and 85: Appendix C The width of the dischar
Page 86 and 87: Appendix C Other Pipe Details At th
Page 88 and 89: D Figure C-4: Design guide for a fa
Page 90: www.dsevic.gov.au

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