Highway Slope Manual

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55 6. LANDSCAPE ASPECTS 6.1 GENERAL The design of a slope should not only take into account the stability, cost and maintenance requirements but should also consider the aesthetic aspects of the slope (Works Branch, 1993). The aesthetic design should aim to complement the landscape and visual character of the areas along the road and to improve the overall visual quality of its setting. The designer should consider the need for advice from landscape architects, both at the design stage and during construction. Such advice is particularly important at locations of high visual sensitivity. In general, to achieve a balanced slope design that will satisfy both the engineering and aesthetic requirements, geotechnical engineers and landscape architects should work together as a team from inception of the project to develop an integrated solution. Integration of landscape considerations within the various stages of the planning, slope design, construction and maintenance processes is illustrated in Figure 6.1 and discussed below. Conflicts may arise between the engineering and landscape requirements. In such cases, safety considerations should take precedence. Figure 6.1 Integration of Geotechnical and Landscape Design into the <strong>Slope</strong> Design, Construction and Maintenance Processes
56 For the control of visual impact of new slopes, the use of sprayed concrete or other hard surface on slopes should only be considered as a last resort and only after other techniques have been explored and found not practical. This principle should also be adopted for both preventive maintenance and upgrading works to existing slopes. Detailed guidance on landscape treatment and bio-engineering techniques for manmade slopes and retaining walls is presented in GEO Publication No. 1/2000 (GEO, 2000). 6.2 PLANNING OF LANDSCAPE WORKS For new road or road improvement projects involving slope works, it is necessary to consider landscape, visual and ecological impact issues as part of the planning process. For major projects, a landscape, visual and ecological impact assessment should be part of the statutory Environmental Impact Assessment (Environmental Protection Department, 1997 and 1998). This will require the input of landscape architects at various stages of the project and due allowance should be made for programming and funding arrangements. The resources to be allocated to the landscape/visual design of a roadside slope should be proportional to the visual sensitivity of the location. As a guide, the provision for landscape works should be around 10% but could be up to 20% of the cost estimate for the slope works for very sensitive locations. 6.3 DESIGN CONSIDERATIONS 6.3.1 General In planning new highway and road improvement projects, areas of high aesthetic value should be avoided and, where unavoidable, every effort must be made to minimise the overall impact and to preserve the balance of every aspect of the environment. Existing landscape features, e.g. trees and rock outcrops, should be retained where possible. It is important that the engineering and landscape solutions are not developed in isolation from each other, but as part of an integrated process. The aesthetic design solution of a slope should take account of the specific local environmental characteristics and setting (e.g. colouring, micro-climate and vegetation types). Even if two slopes at different locations have similar geotechnical characteristics, the aesthetic considerations may be quite different. For example, attention should be given to the colours in the surrounding landscape as well as textures of vegetation and rock which might be complemented in the final design (Department of Transport, 1992). <strong>Slope</strong>s in urban or urban fringe areas demand solutions that are different from those appropriate to rural, rural fringe or Country Park areas. Consideration should be given to adopting solutions that provide opportunity to enhance the environment with vegetation. Where vegetation is to be established on a slope, the planting design should as far as practicable seek to promote the development of ecologically balanced plant communities, preferably using native species in the area, with a view to supporting wildlife as well as to
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HIGHWAY SLOPE MANUAL GEOTECHNICAL E
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2 。 The Government of the Hong Ko
Page 5 and 6: 4 STEERING COMMITTEE: Geotechnical
Page 7 and 8: 6 Page No. 3. SITE INVESTIGATION 33
Page 9 and 10: 8 Page No. APPENDICES APPENDIX A -
Page 11 and 12: 10 LIST OF FIGURES Figure No. Page
Page 13 and 14: 12 LIST OF LATES Plate No. Page No.
Page 15 and 16: 14 [BLANK PAGE]
Page 17 and 18: 16 year (Evans et al, 1998), they h
Page 19 and 20: 18 Plate 1.4 Landslide at Ching Che
Page 21 and 22: 20 Plate 1.8 Steep Natural Terrain
Page 25 and 26: 24 Notes: (1) The projects in the P
Page 27 and 28: 26 of the geotechnical hazards and
Page 29 and 30: 28 Table 2.2 Geotechnical Haards Th
Page 31 and 32: 30 for carrying out a GA is given i
Page 35 and 36: 34 Table 3.1 Potential Uses of Diff
Page 37 and 38: 36 or features such as dykes or fra
Page 39 and 40: 38 movement monitoring and control
Page 41 and 42: 40 landslide debris, and the nature
Page 43 and 44: 42 Notes: (1) This Figure is based
Page 45 and 46: 44 Table 4.5 Recommended Minimum Fa
Page 49 and 50: 48 Plate 5.1 Surface Runoff Channel
Page 51 and 52: 50 Cascades, with cover where neces
Page 53 and 54: 52 (a) Trash Grill at Inlet of Cros
Page 55: 54 5.2.3 Drainage Improvement Works
Page 59 and 60: 58 Plate 6.3 Pattern and Texture Pl
Page 61 and 62: 60 ighways are environments with a
Page 63 and 64: 62 Filling operations for a highway
Page 65 and 66: 64 Blasting is the most common meth
Page 67 and 68: 66 Notes: (1) The responsibility fo
Page 69 and 70: 68 Results of Rockfall Protective B
Page 73 and 74: 72 overseeing the maintenance of th
Page 75 and 76: 74 In addition to the slope upgradi
Page 77 and 78: 76 after each heavy rainstorm event
Page 79 and 80: 78 d n n d d d d d d d
Page 81 and 82: 80 event of a landslide should be b
Page 85 and 86: 84 Federal Highway Administration (
Page 87 and 88: 86 Highways Department (1996). Mana
Page 89 and 90: 88 Wong, H.N., Pang, L.S., Wong, A.
Page 95 and 96: 94 key natural terrain and man-made
Page 97 and 98: 96 and details of all existing slop
Page 101 and 102: -AA (v) relevant services and utili
Page 103 and 104: -A2 (m) (n) 1dentify any statutory
Page 105 and 106: -A4 Notes: (-) An example of a prog
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106 [BLANK PAGE]
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108 Wong, C.K.L. (1998). The New Pr
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110 of slopes and slope owners and
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112 [BLANK PAGE]
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114 (iv)subsidence of ground or roa
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