PROMOTION OF KABUL METROPOLITAN AREA DEVELOPMENT: CAPACITY DEVELOPMENT PROJECT

Transcription

1 No. Japan International Cooperation Agency (JICA) Ministry of Urban Development Affairs (MUDA) Kabul Municipality Dehsabz City Development Authority (DCDA) PROMOTION OF KABUL METROPOLITAN AREA DEVELOPMENT: CAPACITY DEVELOPMENT PROJECT LAND PREPARATION PLAN FOR THE DEHSABZ SOUTH AREA February 2012 RECS International Inc. T. & Associates Yachiyo Engineering Co., Ltd. EID J R

2 Japan International Cooperation Agency (JICA) Ministry of Urban Development Affairs (MUDA) Kabul Municipality Dehsabz City Development Authority (DCDA) PROMOTION OF KABUL METROPOLITAN AREA DEVELOPMENT: CAPACITY DEVELOPMENT PROJECT LAND PREPARATION PLAN FOR THE DEHSABZ SOUTH AREA February 2012 RECS International Inc. T. & Associates Yachiyo Engineering Co., Ltd.

3 Table of Contents Chapter 1 Existing Conditions of Dehsabz South Area Related to Land Preparation Plan Location and Topography Geographic and topographic contexts Existing topography and objects in Dehsabz South area Basic Principles of Structure Planning Related to Land Preparation Plan Creation of water-rich spaces to ensure vegetation environment Utilization of existing topography for cost reduction...5 Chapter 2 Basic Principles of Land Preparation Planning Use of Land Preparation Plan and Planning Procedure Use of land preparation plan Procedure of land preparation planning Purposes of Land Preparation Planning Planning to ensure safety from disasters Proper treatment of drainage Minimization of earth works Expression of land preparation plan with maps Expression with contours Advantages of using contour lines Physical models...13 Chapter 3 Examination of Land Preparation Plan for Dehsabz South Area Considerations for Selection of Land Grading Methods Land grading methods Considerations for land grading planning Planning for Land Lot Levels Determination of land lot levels and gradients Relationships between levels of land lots and roads Planning for Road Levels Determination of cross-sectional gradients Determination of height for intersection and other critical locations Planning for Main Drainage Routes Rainwater drainage Wastewater drainage Chapter 4 Quantity of Earthworks Calculation of Quantity of Earthworks Development costs and quantity of earthworks Earthwork calculation Approximate Quantity of Cutting and Embanking Earthworks Compilation of earthworks for cutting and embanking Conversion factors for soil quantity Excess soil disposal...36 Chapter 5 Considerations for Further Planning and Design Consideration on Soil Transport Soil transport plan Outline of soil transport plan Consideration on Disaster Planning...38 i

4 List of Tables Table 1 Conversion Factors of Soil Quantities Used in Japan...36 Table 2 Use of Machinery by Transport Distance...38 ii

5 List of Figures Figure 1 Location and Topography of Dehsabz South Area and Its Surroundings...1 Figure 2 Existing Topography of Dehsabz South Area...2 Figure 3 Existing Roads and Objects in Dehsabz South Area...3 Figure 4 Dehsabz South Area Land Use Plan and Preservation and Use of Gullies...4 Figure 5 Proposed Water and Greenery Network Development by Utilizing Local Topography...5 Figure 6 Context and Scope of Land Preparation Planning...6 Figure 7 Steps of Planning, Design and Construction with Land Preparation Planning...7 Figure 8 Example of Primary and Secondary Land Preparation Plan for Residential Complexes...8 Figure 9 Procedure of Land Preparation Planning...9 Figure 10 Primary and Secondary Land Preparation Planning and Role of Master Developer...9 Figure 11 Expression of Land Preparation Plan by Contour Lines and Supplementary Data...10 Figure 12 Distinction between Land to Be Transformed and Preserved Expressed by Contours...11 Figure 13 Contour Line Expression of Complicated Land with Rounding...11 Figure 14 Expression of Land Preparation Plan for Residential Development Overlaid on Existing Topography...11 Figure 15 Expression of Land Preparation Plan for Apartment and Small Factory Development Overlaid on Existing Topography...12 Figure 16 Image of Land Grading and Development by Contour Lines...12 Figure 17 Examples of Land Preparation Plans by Contour Lines...13 Figure 18 Physical Model Based on Contoured Land Grading Plan...13 Figure 19 Two Types of Land Preparation for Sloping Land...14 Figure 20 Treatment of Differences in Land Levels in Land Preparation...14 Figure 21 Areas to Be Preserved in Dehsabz South Area...15 Figure 22 Example of Primary and Secondary Land Preparation for Commercial/Business Area...16 Figure 23 Treatment of Difference in Land Levels for Residential Development...16 Figure 24 Division of Drainage from Residential Blocks to Respective Access Roads...17 Figure 25 Relationship between Residential Lot Level and Road Level...17 Figure 26 Rounding Method of Land Preparation for Parks and Greenery (Example)...18 Figure 27 Illustration of Land Level Setting for Land Lots along Wide North-South Road...18 Figure 28 Determination of Road Levels and Cross-sectional Gradients (Example)...19 Figure 29 Determination of Crossfall Gradients and Levels of Intersection (Example)...19 Figure 30 Cross-section Gradients at Point of Road Gradient Changes (Example)...20 Figure 31 Planned Levels of Road Intersections in Dehsabz South Area...21 Figure 32 Determination of Road Levels at Intersection between Artery Road and Major Gully (Example)...22 Figure 33 Rainwater Drainage to Gullies and Channels Nearby (Example)...22 Figure 34 Use of Exiting Channels for Drainage in Southern Part of Green City...23 Figure 35 Proposed Rainwater Drainage Routes by Roads, Gullies and Channels in Dehsabz South Area...24 Figure 36 Schematic Drawing for Agricultural Park along Eastern Borders and Land Preparation Plan for the Area...25 Figure 37 Proposed Wastewater Drainage Main Routes...26 Figure 38 Primary Land Preparation Plan for Dehsabz South Area (1/3)...27 Figure 38 Primary Land Preparation Plan for Dehsabz South Area (2/3)...28 Figure 38 Primary Land Preparation Plan for Dehsabz South Area (3/3)...29 Figure 39 Preparation of Land Preparation Plan in Detail (Example)...30 Figure 40 Earthwork Calculation Methods...31 Figure 41 Image of Earthwork Calculation by Mesh Method...31 Figure 42 Expression of Earthwork Calculation Data (Example)...32 Figure 43 Detailed Example of Earthwork Calculation by Mesh Method...32 Figure 44 Earthwork Calculation for Cutting and Banking by Mesh in Dehsabz South Area (1/2)...33 Figure 44 Earthwork Calculation for Cutting and Banking by Mesh in Dehsabz South Area (2/2)...34 Figure 45 Approximate Earthwork Calculation for Cutting and Banking in Dehsabz South Area...35 iii

6 Figure 46 Soil in Different States...36 Figure 47 Expression of Soil Transport Plan (Example)...37 Figure 48 Cost of Construction by Soil Transport Machinery and Distance in Japan...38 iv

7 Abbreviations DCDA FH GH JICA KCORR KNC MUDA Dehsabz City Development Authority Formation height Ground height Japan International Cooperation Agency Kabul city outer ring road Kabul New City Ministry of Urban Development Affairs Units of Measure cm ha m m 3 centimeter hectare meter cubic meter v

8 CHAPTER 1 EXISTING CONDITIONS OF DEHSABZ SOUTH AREA RELATED TO LAND PREPARATION PLAN 1.1 Location and Topography Geographic and topographic contexts The Kabul new city is planned in a large territory of 740km 2 to the northwest of the Kabul city with a planned population of 1.5 million by 2025 to cope with the rapidly increasing population in the capital city. The Dehsabz South area constitutes part of the new city, planned with a population of about 400,000 in 2025 to be accommodated in about 5,000ha land. The Dehsabz South area is located in the desert-like lowland between the Kabul city and the Safi Mountains in the northwest (Figure 1). The land is gently inclined to the west at a gradient of 1-5%, and dissected by many gullies created by snowmelt water from the eastern mountains. Many rural settlements and villages are found in the southwest and the east of the area. Safi Mountains Dehsabz South Area Center of Kabul City Kabul River Figure 1 Location and Topography of Dehsabz South Area and Its Surroundings 1

9 1.1.2 Existing topography and objects in Dehsabz South area (1) Topography The local topography in the Dehsabz South area has slightly higher gradients at about 3% in the east and the southern ends at an elevation of 1,830-1,860m (Figure 2); 1% in the western half of the area at 1,730-1,800m; and 2% in the east and the south at 1,830-1,860m. The land is generally inclined to the northwest to west with largely flat or gently inclined land. There are five major gullies, 5-10m deep, dissecting the Dehsabz south area from the east to the west. Extending from these gullies are smaller gullies forming together a tree-like pattern of gullies. Figure 2 Existing Topography of Dehsabz South Area (2) Existing roads and buildings There are roads in and around the Dehsabz South area that link the rural settlements and villages around the area with the Kabul city for the daily needs of the residents. Major roads crossing the area consist of the Bagram Road passing through the area in the north-south direction, the southwest-northeast road linking scattered villages, and the east-west road along the borders with the 2

10 Afghan Army maneuvering ground in the south (Figure 3). There are many ongoing residential developments along the Bagram Road and additional land and housing are in preparation, taking advantage of the artery road providing good access. Of these developments, the Mohamadiah town in the northwest has started to accept residents. Along the southwest-northeast road, a residential complex, called the Green City, is under construction. Outlets of karez or underground water channels are found within the area to provide limited water for vegetation. Many brick kilns exist in the lowland part of the area in Dehsabz. In the Dehsabz South area alone, there are tens of brick factories, and they are expanding recently reflecting the constriction boom. New residential development (inhabited) Karez Channel Bagram Road New residential development Existing residential village Figure 3 Existing Roads and Objects in Dehsabz South Area 3

11 1.2 Basic Principles of Structure Planning Related to Land Preparation Plan Creation of water-rich spaces to ensure vegetation environment (1) Preservation of rivers and gullies Major rivers and gullies are preserved in principle in the Dehsabz South area structure plan. This principle has been adopted to 1) ensure proper discharge of a large amount of snowmelt during early spring, 2) reduce development cost by suppressing land preparation cost, and 3) avoid embankment when the ground stability is uncertain. Rivers and gullies should be preserved as is by locating parks and greenery along them. At the same time, efforts should be made to improve the viability of development by effectively utilizing the river/gully-side parks and greenery. They include control on the size of parks and greenery area, minimization of intersections between roads and greenery considering preparation costs, and maximization of land to be used for residential purposes. (2) Creation of water retention and infiltration spaces with gullies It is desirable to make effective use of snowmelt during early spring to ensure better water availability for the vegetative environment in the dry land. The structure plan has proposed 1) large water retention and infiltration spaces for temporary water storage upstream along the eastern borders of the area, 2) network of water and greenery linking gullies with north-south canals, and 3) step-wise lower riverbeds with weirs installed in the gullies (Figure 4). Temporary water storage within the Dehsabz South area will also help develop and maintain the agricultural land and vegetative environment in the downstream areas. This is an important consideration under the climatic conditions with limited water availability. Also, the existing topography should be effectively utilized for the proposed water and greenery network (Figure 5). Water retention zone for meltwater and floodwater Figure 4 Dehsabz South Area Land Use Plan and Preservation and Use of Gullies 4

12 Eastern desert area Water retention zone KNC Central Park Eco Park Community park General athletic park Channels & Gullies Dehsabz South Area Figure 5 Proposed Water and Greenery Network Development by Utilizing Local Topography Utilization of existing topography for cost reduction (1) Land preparation in line with existing topography Land preparation involves transformation of existing topography to make it fit to the planned use of the land, involving cut and fill of land. The transformation should be kept minimal necessary since cut and fill of land will involve: 1) large costs to move soil, 2) longer construction period due to large earth works, 3) treatment of drainage and associated problems inside and outside the land, and 4) transformation of local landscape, settlements and environment unique to the area. It is, therefore, meaningful to examine the future land morphology planned to fit to the existing topography in land preparation planning. In the Dehsabz South area, the land gently sloping northwestward is effectively utilized in land preparation. (2) Soil balance within each land lot and waste soil disposal site In addition to reduction of total volume of earthworks, soil balance for cutting and filling works should be considered. Excess cutting or filling would necessitate soil transport from or to the development site. Soil transport over long distance would involve large costs. It is, therefore, ideal to balance cutting and filling works within the site. Amount of earth works tend to vary from estimates as more detailed planning proceeds. It is thus desirable that a site for waste soil disposal is presumed during an early stage of planning for cases where excess cutting or filling is involved. In the Dehsabz South area structure planning, a waste soil disposal site is determined in the southeast of the area, while the soil balance is examined in each sizeable parcel to minimize the waste soil. 5

13 CHAPTER 2 BASIC PRINCIPLES OF LAND PREPARATION PLANNING 2.1 Use of Land Preparation Plan and Planning Procedure Use of land preparation plan (1) Needs for land preparation plan Land preparation is to transform land morphology from its natural state to another suitable for specific land use and necessary to level land for roads, properties and other structure. A land preparation plan is used with the corresponding land use plan to facilitate the understanding of the latter by providing the third dimension to the land use. The land preparation plan specifies the locations, forms and heights of infrastructure facilities and also the scope of preservation of the land's natural status. Determination of the scope of preservation of natural land conditions is important in protecting the existing houses and structures as well as the natural landscape and other conditions. Large-scale development such as a new town development involves construction of facilities for transportation, parks and greenery, drainage, disaster prevention, utilities and other functions for various residential and other developments. Therefore, land preparation for such development involves more than just grading (Figure 6). Existing Topography Various Plans (ideal) Modification of land use plan, urban infrastructure, development plan, etc. Feedback Land Preparation Planning Considering land use and buildings, transportation, parks and greenery, drainage, land grading, landscape, etc. Third Dimension Planning land plot level setup, main road slope and height setup, main drainage route study, soil transport study, etc. Future Topography Figure 6 Context and Scope of Land Preparation Planning (2) Use of land preparation plan i) Interpreting various plans in reference to topography Planning is usually conducted on a plane, and thus only ground plans are regarded as plans. To realize and substantiate the land morphology in the future, however, transformation of the existing land to fit the planned use should be considered. Land preparation planning deals with land levels and elevations so that it links a land use plan with urban infrastructure development plan, site plan, landscape plan and other plans. By interpreting different plans on the local topography, consistency between them with respect to the spaces that each plan is designed to create can be examined. 6

14 A land use plan and a land preparation plan should be prepared together through feedbacks between them. Just as various plans are prepared in steps from macro to detailed planning level, a land preparation plan is also prepared in steps. ii) Substantiating urban infrastructure development plans Of urban infrastructure development plans, drainage and road plans are particularly related to local topography. In each of the plans, elevations of facilities need to be set by land preparation planning. For drainage planning, the principle is to drain rainwater and wastewater by gravity to reduce the development cost. In road planning, gradients need to be determined together with road width and cross-section to allow safe passage of passengers and vehicles. The land preparation planning has a role to determine the levels and locations of various urban infrastructure facilities, which will bring about those conditions for drainage and transportation. iii) Substantiating site plans To establish housing and other facilities as planned by the land use plan, land needs to be prepared for them. In planning land development for these buildings, attention should be paid to proper dimensions, land levels in relation to road levels, disaster prevention, and others. A land preparation plan reflects these considerations in the development plan. iv) Preserving existing topography and objects It is common in urban development to encounter a situation in which the existing environment, topography, landscape and other conditions should be preserved and important facilities and heritage, houses, and buildings in the existing settlements should be protected. Also, the existing trees and vegetation, soil and other natural conditions may need to be preserved to maintain or enhance favorable natural environment. A land preparation plan may determine areas to be preserved and transformed, and set land levels that will ensure such designation Procedure of land preparation planning (1) Steps of land preparation planning i) Primary or rough land preparation and secondary or detailed land preparation In large-scale urban development, it is often the case that a plan for buildings is prepared after land transfer. In this case, land preparation is conducted in steps. It consists of primary or rough land preparation planning to determine the basic structure and morphology of the land, and secondary or detailed land preparation planning to be made based on the site planning for buildings and other facilities, which is usually done after land transfer to developers (Figure 7). Planning & Design Stage Structure Plan [scale=1/5,000] Land Use Planning Infrastructure Planning Land Preparation Planning etc. Land Preparation Planning Development Plan (detailed plan/official) [scale=1/2,500-1/1,000] Land Preparation Planning Implementation Design [scale=1/1,000-1/500] Construction Stage Rough Land Preparation by Master Developer Main Infrastructure Construction by Master Developer Sell Land (Super Block) Detailed Land Preparation by Sub Developer Building and Infrastructure Construction in Super Blocks by Sub Developer Figure 7 Steps of Planning, Design and Construction with Land Preparation Planning 7

15 A land preparation plan is first prepared for primary or rough land preparation in view of step-wise land preparation works (Figure 8). A plan for primary land preparation, however, should not constrain detailed land preparation planning, and thus the primary land preparation plan is prepared with images of detailed land preparation. Just as other kinds of planning, details are added as planning and design works proceed. Source: Tama New Town Planning and Design Manual, 1976 Figure 8 Example of Primary and Secondary Land Preparation Plan for Residential Complexes ii) Procedure of land preparation planning Since land preparation planning mainly determines land levels and drainage, the environment, geology and soil conditions of the development area should be examined in advance. Based on the examination, civil work conditions for planning and design are determined and a land preparation plan is prepared. In preparing the land preparation plan, consistency with land use plan and other related plans should be ensured as a matter of course. The land preparation plan determines land lot levels, road gradients, and the drainage plan based on them. After examining the land preparation plan, a land-grading map that shows the future terrain is prepared. Based on this map, the amount of earth works is calculated and soil balance is checked with cutting and embanking. If the cutting and embanking do not balance, the results should be fed back to modify the land preparation plan. The land preparation plan should be prepared in view of soil transport plan and disaster prevention plan associated with construction works. The procedure of land preparation planning is shown in Figure 9. (2) Land preparation plan prepared at this time The land preparation planning conducted at this time corresponds to primary or rough land preparation planning as the applicable scale of map is 1:5,000. It aims to clarify the overall land preparation of the Dehsabz South area and drainage conditions with respect to land and water. The primary or rough land preparation plan thus prepared will establish principles for land preparation and will be used by the Master Developer to control the preparation of primary and secondary land preparation plans for individual land lots or blocks (Figure 10). 8

16 Investigation and Condition Setup Environment research, geology and soil investigation Condition setup for earthwork Land use planning, etc. Land Preparation Planning Land preparation plan study (rough/detailed land preparation) - Land plot level setup - Main road slope and height setup -Main drainage route study Drawing of land preparation plan Calculation of amount of earthworks Detailed Planning Stage + Soil transport planning Design Stage + Disaster prevention planning Figure 9 Procedure of Land Preparation Planning Initial Development by Master Developer Planning, Design and Construction of - Infrastructure (structural level) - Land (super blocks) (1) Construction Construction Confirmation (2) Development Control Sales Coordination 2nd Development by Sub-Developers Planning, Design and Construction of - Infrastructure (in super blocks) - Land plots - Buildings Figure 10 Primary and Secondary Land Preparation Planning and Role of Master Developer 2.2 Purposes of Land Preparation Planning Planning to ensure safety from disasters Any urban development should be planned to ensure the safety of residents not only within the development area but also outside the area. The planned urban development should not render surrounding areas more vulnerable to disasters. It is thus necessary to formulate a highly safe and disaster-free land preparation plan. Since the existing ground has been stabilized over a long time, it is desirable to prepare land in forms close to the existing topography as a matter of principle. Transformation of land should be examined in line with the local geology and the existing ground. For instance, for the areas vulnerable to erosion by rainwater, land should be prepared with a small gradient. In areas where differences in elevation converge, land should be prepared with safe slopes or retention walls Proper treatment of drainage It is the basic requirement of land development for housing to create sanitary land free from disease prone conditions. To ensure such land development, proper drainage is most important. A drainage plan should be prepared to prevent stagnation of rainwater anywhere. As the original topography is transformed by land preparation, it is also vital that the transformation will not cause adverse effects to downstream areas during discharges of rainwater. 9

17 2.2.3 Minimization of earth works The amount and types of civil works are the main factors that affect the costs of urban development. In particular, the amount of earth works should be minimized for economy of urban development. It is also important to balance cutting and banking as much as possible within the development area to reduce soil transport to and from outside. Land preparation planning by effectively utilizing natural topography contributes to reduction of earthworks and thus development cost. 2.3 Expression of land preparation plan with maps Expression with contours As a land preparation plan deals with three-dimensional topography, it is essential to devise such methods of expression for maps and drawings. Usually, existing and future topography is expressed with a ground plan with many cross section plans. In planning for land preparation, however, ground plan and elevation need to be treated together, and thus it is desirable to express elevation on the same ground plan. It is thus recommended in planning that future topography should be expressed with contour lines. In this expression, elevation and gradients of key points are also added as supplementary information (Figure 11). Source: Civil engineering design drawing standards, Japan Society of Civil Engineers Figure 11 Expression of Land Preparation Plan by Contour Lines and Supplementary Data Advantages of using contour lines (1) Expression of transformation and preservation of topography The land preparation plan prepared at this time uses contour lines to express the transformed land morphology after land grading, solid lines to express planned contours, and dotted lines to express areas where the existing conditions will be preserved (Figure 12). This method of expression facilitates the understanding of graded areas and land relief. Planned areas are easily identified as well. (2) Expression of complicated slopes In actual urban development, all the land would not be either flat or slope with the fixed gradient. Some complicated land should be expressed by rounding and other forms. Land preparation planning with contour lines allows expression of such complicated land morphology (Figure 13). (3) Expression overlaying existing conditions and plan In preparing a land-grading plan, it is important to understand where and to what extent changes will be introduced. Expression with contour lines allows overlaying the existing topography and the future topography on the same land preparation plan (Figures 14 and 15). 10

18 Existing topography Sloping land w/ safe gradients Banking area Cutting area Existing topography Existing topography Source: ibid. Retention walls Figure 12 Distinction between Land to Be Transformed and Preserved Expressed by Contours Source: ibid. Figure 13 Contour Line Expression of Complicated Land with Rounding Source: ibid. Figure 14 Expression of Land Preparation Plan for Residential Development Overlaid on Existing Topography 11

19 Source: Site Planning (1984), K. Lynch & G. Hack Figure 15 Expression of Land Preparation Plan for Apartment and Small Factory Development Overlaid on Existing Topography (4) Information sharing with contour line expression The expression of the land preparation plan with contour lines also facilitates the relationships between the levels of land lots in relation to roads and other urban infrastructure facilities (Figure 16). It is important to facilitate the understanding of planners but equally important is to convey proper information to them. It is highly recommended that the land preparation plan be expressed by contour lines and that the levels, gradients and other data be provided at key locations to complement the plan (Figure 17). Figure 16 Image of Land Grading and Development by Contour Lines 12

20 Source: Tama New Town Planning and Design Manual, 1976 Figure 17 Examples of Land Preparation Plans by Contour Lines Physical models It is also useful to produce physical models to provide three-dimensional expression for easy understanding. Future topography is expressed by adding layers from lower parts to upper parts. This process facilitates the understanding of land grading following contour lines (Figure 18). Figure 18 Physical Model Based on Contoured Land Grading Plan 13

21 CHAPTER 3 EXAMINATION OF LAND PREPARATION PLAN FOR DEHSABZ SOUTH AREA 3.1 Considerations for Selection of Land Grading Methods Land grading methods (1) Land grading in line with existing topography Methods of land preparation consist of land grading to create extensive flat land and land grading in line with the existing topography. The former will generate the largest area of land that can be effectively utilized, but a large quantity of earthworks is involved and spaces thus created tend to be rather monotonous. The land preparation conducted at this time utilizes the existing topography characterized by gently sloping land toward the northwest at a 1-3% gradient. The levels of land lots and roads are determined in line with this general topography. (2) Sloping land preparation Land preparation for sloping land establishes either terraces with flat land created by retaining walls or sloped land (Figure 19). The land preparation conducted at this time adopts sloped land preparation so that further land preparation by individual developers may be undertaken in a more flexible way. Land preparation by retaining walls Sloped land preparation Figure 19 Two Types of Land Preparation for Sloping Land (3) Treatment of difference in levels due to slope or retention wall The flat land and slopes created by cutting and filling should be made stable for future use. Therefore, in areas where differences in land levels are involved, the difference is treated with slope or retention wall (Figure 20). Since the construction costs are much higher for retention walls, it is desirable that the level differences should be resolved with slopes as much as possible. Stability of slopes and retention walls depends on soil property, which should be examined carefully before determining slopes and height standards. Berm Small embankment Land plot Slope gradient Sloped land w/ safe gradients Retaining wall Source: Shin-taikei Doboku Kogaku, 78-1, Japan Society of Civil Engineers Figure 20 Treatment of Differences in Land Levels in Land Preparation 14

22 3.1.2 Considerations for land grading planning (1) Determination of land to be preserved In accordance with the principles embodied in the structure plan, major gullies will be preserved to ensure proper drainage of snowmelt together with the existing karez providing limited water for the area and greenery. The existing settlements and villages in the southwest and the two residential areas being developed in the area will also be preserved as much as possible (Figure 21). Main gullies New residential development (inhabited) Bagram Road Channel Existing village Karez New residential development Figure 21 Areas to Be Preserved in Dehsabz South Area (2) Creation of residential land with maximum flexibility for further development It is generally possible to increase the area of flat land by increasing earth works to reduce slope land and retention walls. It is not desirable, however, for technical and economic reasons to create flat land for most part of the land to be developed. In order to create as much residential land as possible at smallest quantity of earth works, it is important to utilize high land and low land as they area. Most land thus generated is expected to be further developed by private developers. Therefore, it is another important consideration that the maximum flexibility is allowed for such secondary developments as well as infrastructure development in primary land preparation. (3) Avoidance of needs for large structure Large structure such as bridges and tunnels involve large costs as compared to land preparation costs. Construction of such large structure should be avoided as much as possible. Crossings of large gullies by roads should be treated by embankments as much as possible rather than bridges. This is adopted for the existing crossings of gullies by the Bagram Road. Also, the treatment of differences in land levels should adopt slopes in principle, avoiding costly retention walls. 3.2 Planning for Land Lot Levels Determination of land lot levels and gradients In planning for land lot levels, consistency of the land use and other related plans should be pursued for spatial images, while balancing soil for cutting and embanking. On this basis, the land lot levels and gradients are determined comprehensively considering the height to be ensured for each land lot and a frontage road, lot shape, site plan for buildings, directions of sunshine and other natural conditions, road gradient, and the relationship between the land lot and its frontage road. It is important in primary land preparation planning to visualize detailed land preparation planning. The primary land preparation, however, should not constrain the flexibility in which developers can undertake large-scale development in a super block. It is important for primary land preparation to allow flexibility for further developments by providing only a site plan (Figure 22). 15

23 When sloping land preparation is adopted, slopes within land lots should not create differences in height too large to prevent planned land uses (Figure 23). As the existing topography in the Dehsabz South area is gentle, this problem is unlikely to occur, and the land preparation at this time will create slopes of 5% at most. Source: Tama New Town Planning and Design Manual, 1976 Figure 22 Example of Primary and Secondary Land Preparation for Commercial/Business Area Land plot Road Road Source: Shin-taikei Doboku Kogaku, 78-1, Japan Society of Civil Engineers Figure 23 Treatment of Difference in Land Levels for Residential Development Relationships between levels of land lots and roads (1) Drainage at each land lot In determining land lot levels, it is important to treat drainage properly within each lot so that it will not flow into and accumulate in any land lot. In general, the drainage from land lots should be discharged through roadside drains and channels eventually to rivers and ocean (Figure 24). The level should be made higher for land lots than roads and channels nearby to allow drainage from the former by gravity. Land grading for a super block should be planned in consideration of drainage from individual blocks to neighborhood roads to be developed. 16

24 Figure 24 Division of Drainage from Residential Blocks to Respective Access Roads (2) Access to each land lot In principle, the level of any land lot should be higher than the level of its access road. Difference in the levels should be small enough for easy access (Figure 25). This principle does not apply to large-scale land lots such as super blocks where public facilities such as schools, parks and other large facilities are to be located. The relationships with respect to the level between land lots and roads affect land uses along the roads. For instance, commercial land requires smooth access from nearby roads, and thus land preparation should minimize the differences in height between the roads and the land lots. In the land preparation planning at this time, the height difference is made particularly small in the circular core zones where commercial and business uses are dominant. For this, the levels of land lots and roads are determined with the slopes between them limited to 10-40cm. Each plot accessible by car. About 6m vertical clearance to be secured for two-level crossing Plot level higher than road level Road level to be determined considering water flow Figure 25 Relationship between Residential Lot Level and Road Level (3) Consideration for rounding Of any land lot, portions to be used for buildings are prepared usually as level ground. For other parts, it is often more desirable to use rounding to connect the higher and the lower grounds smoothly for landscape and other reasons. This method of land preparation is used frequently for parks and greenery (Figure 26). This results in contour lines with varying spaces between lines. 17

25 Figure 26 Rounding Method of Land Preparation for Parks and Greenery (Example) (4) Land lot levels along wide north-south roads Since the Dehsabz South area slopes gently toward the west, difference in levels occur on both sides of any north-south road having wide right-of-way. In such a case, the levels of the road and land lots along it should be set such that the land lots on the eastern and the western sides will be both prepared for residential lots of convenient use. Land plot level to be carefully determined if widely different from its front road level Level gap on both sides of road Figure 27 Illustration of Land Level Setting for Land Lots along Wide North-South Road 3.3 Planning for Road Levels Determination of cross-sectional gradients (1) Handling of road traffic From the traffic safety point of view, the cross-sectional gradient of any road should not be too large. In the present planning, the maximum gradient is set at 5% for the main artery roads and 2.5% for 18

26 intersections. Land preparation planning is conducted to determine road alignments and levels within these limits on gradients while minimizing the amount of earthworks by aligning roads to the existing topography. It is recommended that the locations where road gradients change be clearly indicated (Figure 28). Source: Civil engineering design drawing standards, Japan Society of Civil Engineers Figure 28 Determination of Road Levels and Cross-sectional Gradients (Example) (2) Road drainage Surface runoffs due to precipitation such as rainfalls on roads and drainage from land lots are in principle discharged promptly by gradients across the roads into roadside drains. The discharged water are collected in rainwater sumps, then led by rainwater pipes, and drained to rivers and others. Rainwater pipes are designed assuming various levels of precipitation including such extreme cases as once-in-five-years rainfall. Excessive rainfalls will not be accommodated by rain pipes, and thus treated by surface runoff. Crossfall gradients of roads should be determined in such a way that floodwater generated by excessive rainfalls will be discharged without stagnation on the road toward rivers, retention ponds or any other drainage areas (Figure 29). Crossfall gradient % % Side ditch Catch basin Source: Shin-taikei Doboku Kogaku, 78-1, Japan Society of Civil Engineers Figure 29 Determination of Crossfall Gradients and Levels of Intersection (Example) (3) Considerations for determination of cross-section gradients Roads aligned on flat land When urban development is undertaken on near flat land, roads are usually aligned more or less in parallel with contour lines. For cases in which existing houses do not allow changes in road levels, roads are aligned with very small gradients. In the Dehsabz South land preparation plan, the Symbol Road passing through the center as the main artery transport axis is aligned almost parallel with the existing contour lines. It is planned for wastewater and drainage from the eastern part of the Dehsabz 19

27 South area to be intercepted by this artery road for effective use and recycling to ensure vegetative environment in this dry zone. When the cross-section gradients of roads are planned under such conditions to reduce the development costs by minimizing earthwork, road sections with extremely small gradients are created. Even with such roads, rainwater drainage is guided to roadsides by the cross-section gradients, and no water stagnation on land lots should occur. When many gullies cross land as is the case in the Dehsabz South area, flooding of roads caused by overflow from rainwater pipes will be relieved easily by drainage into nearby gullied in the distance of 1-2km at most. Thus, roads will not suffer from extended flooding. When a long road section on flat land is involved, routes of sewage and drainage pipes should be carefully aligned so that the pipes of small gradients will not be buried too deep. Change in road gradients At locations where road gradients change, smoothing curve is used to make transition. It is necessary to reflect this smoothing in planning and design at more advanced stage in examining the road access to land lots and determining levels of roads and land lots (Figure 30). Source: Tama New Town Planning and Design Manual, 1976 Figure 30 Cross-section Gradients at Point of Road Gradient Changes (Example) Determination of height for intersection and other critical locations (1) Road intersections The height of an intersection needs to be determined as it prescribes road design together with a road gradient. The height should be specified only by 10cm in the planning (Figure 31). To keep the height difference between roads and land lots and the quantity of earthworks involved from exceeding, it is important to plan both roads and land lots together and determine their levels at the same time. (2) Intersections between artery roads and major gullies At intersections between artery roads and gullies, it is assumed to install box culverts under the roads for drainage from the gullies. For this, the road level should be set at 6m at least from the gully bottom for box culverts (up to 3m high) and pipes (up to 3m high) to be buried underground (Figure 32). 20

28 Figure 31 Planned Levels of Road Intersections in Dehsabz South Area 21

29 Figure 32 Determination of Road Levels at Intersection between Artery Road and Major Gully (Example) (3) Bagram Road It is planned to widen the Bagram Road to 100m and secure its right-of-way accordingly. As the most principal artery road that thrusts the area north and south, the Bagram Road is supposed to be the main drainage route. Due to its characteristics as a military purpose road at present, however, planning and design as well as construction works for the expansion may face difficulties. Therefore, the Bagram Road should not be used as it will be difficult to change the longitudinal alignment of the road to allow proper drainage. 3.4 Planning for Main Drainage Routes Rainwater drainage (1) Drainage by road and gully For drainage by rainwater pipes and sewage pipes, gravity drainage by road gradients should be adopted in principle from the economic perspective. Where drainage by gravity is difficult, it is necessary to pump and transport rainwater but at much higher cost. Rainwater should be discharged through surface runoff on roads and rainwater pipes into gullies nearby. This method of drainage makes use of the main gullies to be preserved for snowmelt discharge (Figure 33). Figure 33 Rainwater Drainage to Gullies and Channels Nearby (Example) 22

30 The dimensions of rainwater pipes tend to become larger as the catchment area for rainfalls becomes larger. By utilizing gullies as drainage channels, the catchment area is subdivided into smaller areas. Consequently, rainwater pipes become smaller and shorter and they can be installed at shallower depths, both contributing to cost reduction. (2) Drainage by channel Drainage by surface runoff should be planned carefully so that rainwater will not accumulate anywhere on the way. In the land preparation plan prepared at this time, drainage by existing channels is planned for the southwestern part where the existing villages are preserved and also for the ongoing Green City (Figure 34). The use of the existing channels in privately owned land should be ensured by proper district planning or agreement with landowners incorporating the use in the conditions for land transfer. Rainwater drainage routes by utilizing roads, gullies and channels in the Dehsabz South area are planned as shown in Figure 35. Figure 34 Use of Exiting Channels for Drainage in Southern Part of Green City (3) Drainage from outer areas A large water retention and infiltration area is planned in the eastern hill of the Dehsabz South area to intercept and temporarily store snowmelt water coming from the outer areas in the further east during spring. This area is planned at this location situated in the upper-most catchment bordering on the areas outside. This area is prepared to have the same elevation to allow stagnation of water for retention and infiltration (Figure 36) Wastewater drainage (1) Area south of KCORR According to the structure plan, a wastewater treatment plant is planned as a water regeneration center at the northern side of the ecological park. The main wastewater drainage routes are planned along the Symbol Road and the road on the western borders of the Dehsabz South area and green areas. Wastewater from the eastern part of the Dehsabz South area should be discharged to the north along the Symbol Road. Wastewater from the western part of the area should be drained along the roads to the west also utilizing the green areas along the borders to the wastewater treatment plant located in the north of the ecological park. (2) Area north of KCORR Wastewater from the western part of the area should be drained along the roads to the west also utilizing the green areas along the borders to the wastewater treatment plant located in the north of the ecological park. Wastewater from the area beyond the KCORR should be treated either by unit processing facilities planned in the local communities or at another treatment plant planned for the Dehsabz North area in the future. Part of the wastewater there may be pumped up for treatment in the Dehsabz South area but it should be avoided. Wastewater drainage routes for the Dehsabz South area are proposed as shown in Figure

31 Existing channels in privately owned land (such use to be ensured by district planning or agreement with landowners at land transaction) Figure 35 Proposed Rainwater Drainage Routes by Roads, Gullies and Channels in Dehsabz South Area 24

32 Figure 36 Schematic Drawing for Agricultural Park along Eastern Borders and Land Preparation Plan for the Area 25

33 Area to be covered by community-based unit processing facilities for wastewater treatment in Dehsabz North area Proposed site for wastewater treatment plant Figure 37 Proposed Wastewater Drainage Main Routes 3.5 The land preparation plan for the Dehsabz South area has been prepared reflecting all the considerations described above. It is shown in Figure 38. Figure 39 illustrates in more detail how the land preparation plan is prepared. 26

34 Contour line of newly prepared land Contour line of existing topography Figure 38 Primary Land Preparation Plan for Dehsabz South Area (1/3) 27

35 Contour line of newly prepared land Contour line of existing topography Figure 38 Primary Land Preparation Plan for Dehsabz South Area (2/3) 28

36 Contour line of newly prepared land Contour line of existing topography Figure 38 Primary Land Preparation Plan for Dehsabz South Area (3/3) 29

37 Figure 39 Preparation of Land Preparation Plan in Detail (Example) 30

38 CHAPTER 4 QUANTITY OF EARTHWORKS 4.1 Calculation of Quantity of Earthworks Development costs and quantity of earthworks (1) Need to assess earthworks quantity at planning stage The quantity of earthworks is one of the factors that affect development costs significantly. Therefore, the amount of cutting and banking should be roughly estimated as part of planning. Not only the total amount but also the amount of cutting and banking to be generated at different locations should be estimated in view of the needs to transport soil during different stages of construction. (2) Land preparation to reduce development costs As development costs rise, the prices of land to be sold to developers rise as well. The development costs should, therefore, be controlled to keep the land prices from rising too much for the developers. What need to be considered in formulating a land preparation plan to reduce the development costs are to 1) minimize the amount of cutting and banking to reduce land preparation works, 2) balance the amount of cutting and banking as much as possible within each land lot or block, and 3) minimize the distance of soil transportation so that simple transport methods can be employed Earthwork calculation (1) Methods The amount of earthworks is calculated by comparing the planned land morphology after land preparation with the existing land morphology (Figure 40). There are a few methods of earthwork calculation such as mesh method, cross-sectional method and contour method. The mesh method is employed at this time. This method calculates the quantity of earthworks in each square mesh area by multiplying the difference in the existing and planned levels at a point in the mesh with the area of the mesh (Figure 41). Existing topography Mesh method Cross-sectional method Figure 40 Earthwork Calculation Methods Cutting Formation height Banking Cutting Ground height Banking Figure 41 Image of Earthwork Calculation by Mesh Method (2) Calculation by mesh method By the mesh method, the difference in the existing and planned levels of each mesh is represented by the level difference at a point in the mesh. Usually, a corner of each mesh is taken to represent the mesh level (Figure 42). 31

39 Ground height (m) GH=1820 FH=1825 Formation height (m) -5 Difference (GH-FH) Figure 42 Expression of Earthwork Calculation Data (Example) The size of the square mesh determines the accuracy of calculation. Since the smaller the mesh, the more accurate the calculation, the mesh size is changed from larger to smaller (e.g., from 100m to 50m and then to 20m) as the planning and designing stage proceeds. However, the number of meshes to cover the area where the quantity of earthworks is to be determined is a more important factor than the mesh size itself. Use of 300 to 1,000 meshes to cover the area is considered sufficient. The primary land preparation planning at 1 to 5,000 scale carried out at this stage uses a 100m mesh to cover the Dehsabz South area with 5,000ha land. A detailed example of earthwork calculation is shown in Figure 43. The calculation results are shown in Figure 44. The quantity of earthworks as indicated by the results, however, should be regarded as only an indication of the conditions applicable to this certain stage of planning and design. As more and more detailed planning and design are undertaken, calculation results will change, and they will never be the same as the actual quantities to be involved in land preparation works. Since the quantity of earthworks is affected by soil conditions, the exact quantity will not be known unless detailed soil tests with boring are conducted. It is most important to utilize the results for the confirmation of planning and design conditions and the coordination of related works. Figure 43 Detailed Example of Earthwork Calculation by Mesh Method 32

40 Figure 44 Earthwork Calculation for Cutting and Banking by Mesh in Dehsabz South Area (1/2) 33

41 Figure 44 Earthwork Calculation for Cutting and Banking by Mesh in Dehsabz South Area (2/2) 34

42 4.2 Approximate Quantity of Cutting and Embanking Earthworks Compilation of earthworks for cutting and embanking (1) Quantities of cutting and banking Quantities of earthworks are compiled for cutting and banking. The compilation should better be made by grouped area of cutting or banking and also by construction area. From the land preparation plan prepared at this time, the quantities of cutting and banking are calculated to be 14 million m 3 each. The details of earthworks for cutting and banking are shown in Figure 45. Area (A) Area (D) Area (E) Area (B) Unit: 10 6 m 3 Area (C) Cutting (net) Banking (net) Area (A) Area (B) Area (C) Area (D) Area (E) Area (F) Total Area (F) Figure 45 Approximate Earthwork Calculation for Cutting and Banking in Dehsabz South Area 35