0061-B1

Calculation of Cut and Fill Volumes by Gis in Forest Road Projecting

Selcuk Gumus^[1], H. Hulusi Acar, Metin Tunay and Ayhan Atesoğlu

Abstract

In Turkey forestry studies are done on an area of 20 million ha in different parts of the country. Working on such a widely dispersed and mostly mountainous area is possible only if these areas have a well-built forest road network. Forest road construction works based on General Forest Road Network Plans, began in Turkey in 1964 and ended in 1974. At present, only 60% of the forest roads we need have been completed.

In this study, the purpose is to calculate the volume of cut and fill with digital terrain models analyses derived from geographical information systems in order to reduce costs. Four forest road projects within the borders of Antalya Forest Regional Directorate, Sütleğen and Lengüme Forest Enterprise have been chosen as the research sites.

Results for each road part have been obtained by calculating cut and fill difference between the volumes of cut and fill, and surface areas have been determined. The grades of the slopes in the terrains where the roads have been constructed have been obtained using a digital terrain model.

Calculating cut and fill volumes, and using these calculations in the phase of determining various choices within the planning process, considerably reduces the expenses and the time spent on the plans and projects of forest roads. These calculations should be taken into consideration before the roads are constructed.

1. Introduction

Using forests for industrial purposes requires intensive, wise and rational use of forests. Forest roads are one af the most important components of this process. These roads also serve for the purpose of transporting raw material, personnel and equipment and also they connect the forest villages to cities. Moreover, they are used by people who want to have a rest in the forest. In this respect, these roads provide economic, social and even culturel benefits (Erdas at al. 1995).

In Turkey, forestry works are done on an area of 20 million ha. which is dispersed in different parts of the country. Working on such a broad, dispersed and mostly mountainous area can be possible only if these areas have a well-built forest road net. Every year approximately 17 million m³ forest product is transported thanks to forest roads and also these roads play an important role in doing other forest works such as protection of forests, cadastre, maintenance, war against erosion and afforestation (Erdaþ at al. 1995).

In Turkey, forest road construction works have started in the first quarter of 1960s as a requirement of General Forest Road Net Plans. For this purpose, directorates of road planning have been set up within forest regional directorates and these directorates have organized the plans of general forest road nets of our country. Until it is planned, forest roads in Turkey have been constructed in accordance with the daily needs. Therefore, a lot roads have been constructed that don't comply with forest road standarts in terms of slope and location (Seckin 1984a).

The route a road follows in a terrain or on a map is called as the alignment of that road. Determining the alignment of forest roads forms the most important and most diffucult part of forest road planning. A wrong determination of the alignment during the planning of forest roads causes technical and economic problems and they cause maintenance problems in the future as well. More than one alignment can be determined among the check points that a road must pass. For that reason, the most appropriate points must be determined by making an alignment search (Seckin 1984b).

Project cost is the leading factor in evaluating the alternatives of forest road alignments (Matthews 1942; Tan 1992). The most important item affecting the cost is excavating works. The volume of cut and fill is calculated first by using cross sections that are taken along the axis of the road in order to calculate the cost of earthworks and expenses related to earthworks. Cut volumes are used in constructing fills. The alignment plan that constitutes the lowest cut and fill volume in evaluating the alternatives of forest roads should be planned as the optimum alignment since it constitutes the lowest cost at the same time (Thuresson 1995).

Various economic, social, culturel and physical data are needed for the organization, management and improvement of the society. Producing information for the good of the society from data groups with computer assisted studies is called information systems. Information systems are based on data. Database is the collection of data regarding an event, an observation or a measurement (Kose at al. 1995). Information is obtained by processing data. Production of information is the result of a process. This process consists of phases such as obtaining, recording, classifying, putting into order, calculating, summarizing, keeping and reterring data and communication. Computer which improves these phases increases the correctness, up to dateness, activity, accessibility and value of information (Köse and Baskent 1993).

Geographical information systems are the most valid means of producing different projects with the evaluation of information related to location and analyses.

In this study, the purpose is to calculate cut and fill volumes with the help of digital terrain models in the projects of forest road alignments by using the contemporary technology. For that reason, some measurements have been done in four distinct regions and cut and fill computations as well as balancing operations have been made on the computer.

2. Material And Method

2.1. Material

The region in question is situated within the borders of Antalya Forest Regional Directorate, , Sütleğen and Lengüme Forest Enterprise. The study area is situated between 36° 30' 00" - 36° 22' 30" north latitudes and 29° 30' 00" - 29° 37' 30" east longitudes.

In the study, four road constructions which are 1 km each have been evaluated.

Road platform and the height of side slopes have been measured with a nivo. The working principle of nivo is like this; after the device is leveled roughly, horizontality of the optical axis is realized with the help of a compensator.

The leveling rods that are used to measure the distance between the points and nivo level are rods usually made of wood which are 3,5 m long and approximately 10 cm wide and which have centimeter division on them.

For the operations of setting up a database and preparing the data for use, Arc/Info software which works under Unix processing system in work station which has a 16 Mb RAM memory and which has 1,6 Gb hard disc capacity.

For database search and for the preparation of maps ArcView 3,2 software which works in PC Pentium II and Windows Millennium processing system has been used.

2.2. Method

In the study, first of all, some measurements have been done at the starting point of side slope on cut, at the end of the ditch, at the both sides af the road platform and lastly at the ending point of the side slope on fill on four roads the construction of which was about the finish. Geometrical height measure is called "nivelman". The main pirinciple of it is to measure the vertical distances from a horizantal level which is constituted on the survey area.

Topographic map has been transformed into the format of Arc/Info layer by digitizing. By making direct digitizing in the Arcedit modüle of Arc/Info software, contour lines which pass once in 50 m. in a 1/25 000 scale topographic map have been tansferred to Arc/Info software with manual digitizing. After entering graphic data, the layer has been prepared for use for GIS by forming topology. Again, information about height has been written into contour lines layer as attribute information by using and interactive screen with Arcedit module. Thus, a digital topographic map has been obtained that can be used in all GIS analyses.

Information regarding height which has been obtained with some measurement on the road construction has been entered into GIS software as point layer. This process has been realized by entering the points as graphics data at which height measurements have been done on a screen displaying the road route and entering the heights measured at each point into the data tables on an interactive screen having a background contour lines layer. Thus, all of the data concerning the four road routes have been recorded as four distinct GIS layers (120 numbered road, 140 numbered road, 180 numbered road, 210 numbered road).

"Cutfill" command has been used four the calculation of cut and fill volume which is one of the geographical analyses of Arc/Info software used in this study and which has GIS software. For this purpose, firstly height model of the whole terrain and then height models of each road piece are formed.

For these operations, digital terrain model has been formed first by making use of a topographic map layer. From this model, a "grid" layer has been obtained including the height data of the whole area. Later, height model of the roads has been found from each piece of road using "polygrid" command of the grid module.

Each piece of road has been activated using grid model including the data of the height of the whole area with "cutfill" command and a file including information about cut volume, fill volume, balance volume, cut area, fill area and volume of the total amount of earthwork that has been moved and grid models displaying the results have been obtained for the road in question.

A layer which includes the slope grade of the study area has been obtained using DTM and "tinarc" command. This layer has been used to calculate the average slope grades. This information has been used to interpret cut and fill volumes of each piece of road. The inquiry has been done TIN module of Arc/Info software.

In order to calculate the cut and fill volume, cut/fill which is a command of Arc/Info has been used. For this command, a grid which has been obtained from digital terrain model and which include the altitudes of the surface of the area, has been formed. The layers that include information about height concerning the segments of road have been transformed into grid. By combining these grids cut and fill volumes and balancing computations have been done.

3. Results And Discussions

The locations of the segment of roads that are the subject of this study on digital terrain model are seen on figure 1. At the same time, this figure symbolizes the position in the real terrain.

Figure 1. DTM of the Study Area and Segments Of Road.

3.1. Resutls of the 120 numbered forest road and discussion

120 numbered road is a B type forest road having a slope of 8%. It has been planned for a terrain which has a side slope of 84,96%. It has been planned in order to make use of the Cedar stands in the area and solve the transportation problem of the villagers living in that area. As the study area, 1 km. part of the existing road has been chosen. Average altitude of the 120 numbered road is 1450 - 1500 m.(Figure 2).

Figure 2. Grid Model of the 120 Numbered Piece of Road.

As a result, the excavation volume of 120 numbered road has been found to be 13030.623 m³ and fill volume 26766.141 m³. That the discrepancy between excavation and fill volumes is 13736.517 m³ is due to high side slope (84.96%) and the grade of the road (8 %).

3.2. Resutls of the 140 numbered forest road and discussion

140 numbered road is a B type forest road having a gradient of 9%. It has been planned for a terrain which has an average side slope of 67,47%. The main aim of its consruction is to make use of the Cedar-Calabrian Pine stands and solve the transportation problem of the villagers living in that area. As the study area, 1 km part of the existing road has been chosen. Average altitude of the road is 1500 - 1550 m. (Figure 3).

Figure 3. Grid Model of the 140 Numbered Piece of Road.

As a result, the excavation volume of 140 numbered road has been found to be 6373.200 m³ and fill volume 15435.822 m³. That the discrepancy between cut and fill volumes is 9061.622 m³ is due to high side slope (67.42%) and the gradient of the road (9%).

3.3. Results of the 180 numbered forest road and discussion

180 numbered road is a B type forest road having a slope of 5,5%. It has been planned for a terrain having an average side slope of 45,38%. The main aim of its consruction is to make use of the Calabrian Pine stands and solve the transportation problem of the villagers. As the study area, 1 km part of the existing road has been chosen. Average altitude of the road is 1100 - 1150 m (Figure 4).

Figure 4. Grid Model of 180 Numbered Piece of Road.

As a result, cut volume of the road has been found to be 4999,850 m³, and fill volume 2941.374 m³. In other words, cut redundancy of the road shows that the straightened line which has been realized at the zero line in the designing phase of the existing road is beneficial for the excavation.

3.4. Resutls of the 210 numbered forest road and discussion

210 numbered road is a B type forest road having a slope of 10%. It has been planned for a terrain having an average side slope of 69,46%. Calabrian Pine stands are available on the area. Another aim of constructing this road is to find a solution for the transportation problem of the villagers. As the study area, 1 km part of the existing road has been chosen. Average altitude of the road is 1050 - 1100 m (Figure 5)

Figure 5. Grid Model of the 210 Numbered Piece of Road.

As a result, cut volume of the road has been found to be 8686,974m³, and fill volume 17844,409 m³. That the discrepancy between cut and fill volume is 9157.434 m³ is due to topographic sitution of the terrain, a side slope of 69,46% and a road slope of 10%.

4. Conclusion

A lot of analyses are realized easily with the help of DTM which has been produced by using GIS which has been realized with the devolopment of information technology. New maps can be produced by processing all the information which has been entered into distinct layers. The information stored in the computer can be collected on the same layer by combining distinct layers. Thus, the information that is too much to be evaluated in a classical map can be read on one digital map and can be evaluated together. Furthermore, thanks to the database, the desired values can be calculated by making a lot of queries.

In this study which has been prepared to calculate the cut and fill volumes with the help of digital terrain models, the results belonging to each piece of road are as follows (Table 1);

Table - 1: Results belonging to the segments of road

As it will save time and money to use digital terrain models which have been used in planning highways, in recent years on planning forest roads which usually pass through mountainous areas, it will be an economic and reasonable approach to use this technology.

Cut and fill computations done in this study have been calculated after the construction of the roads. In practice, using these computations before the construction of the roads in the phase of forming differend alternatives will reduce the money and time spend on planning forest roads on a great scale.

5. Literature Cited

1. Erdas, O., Acar, H. H., Tunay, M., Karaman, A., 1995. Problems and Its Suggestion of Solution Interested in Forest Ergonomy and Production, Forest Roads, Transportation of Forest Products, Forestry Mechanization and Cadastral, Turkey Forestry Report, Karadeniz Technical University, Faculty of Forestry, Publish No:48, Trabzon, 44-79p.

2. Seckin, O. B., 1984a. Arrangement of Forest Road Network and Research Application in Turkey, Istanbul University Journal of Forestry Faculty, Series B, Number 1, 1984, p. 112-125.

3. Seckin, O. B., 1984b. Preparation of Route Plan in a Forest Road Project, Istanbul University Journal of Forestry Faculty, Number 3, Istanbul, p. 92 - 108.

4. Kose, S., Ozkan, M., Baskent, E, Z., ve Gul, A., 1995. Setting up the database of Forest Enterprises, 1.National Blacksee Forestry Congress, Trabzon, Proceedings, Volume 4, p. 308-315.

5. Kose, S. ve Baskent E. Z., 1993. Importance of Geographical Information Systems in Our Forestry, Ministry of Forestry 1. Forestry Council, Report of Papers and Group of Prior Work, Volume 3, 195 - 204, Series No:13, Pub. No: 006, , Ankara.

6. Tan, J., 1992. Planning a Forest Road Network by a Spatial Data Handling-Network Routing System, Acta Forestalica Fennica, 227 p.

7. Matthews, D, M., 1942. Cost Control in the Logging Industry, McGrow-Hýll Book Co, Newyork,

8. Thuresson,T., 1995. Forest Road Optimization Using Gridbased Geographical Informatýon System, Swedish University of Agricultural Sciences Section of Forest Measureation And Management; Umea.

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