Abstract
Harvesting of Forest produce has been a major activity to realize revenue for the government and proper utilization of the matured crop. While extracting the forest produce the economic viability of the extraction has to be looked into to maximize the profits keeping the market value and extraction cost in view. Transportation to the forest produce from the extraction points to the selected depots takes a major share of extraction costs. The objective of the present study is to identify the least cost paths to extract bamboo, in Kollapur sub division of Achampet forest division, to lay new roads where there are no existing ones from selected points andto compare costs if morepaths exists. In the present study an attempt has been made to find out various alternatives of the extraction paths from each coupe to the selected depot, taking landuse/landcover, slope, and drainages, rivers, existing roads, and their condition, bridges, into consideration. The Indian Road Congress( IRC) guidelines were considered in gradient selection. The analysis was carried out using Remote Sensing and GIS, The resistances offered by the different landuse/landcover units, slope, and drains are appropriately weighted through filed investigations and costs assigned. The results revealed that RS/GIS offers effective tools that can be used in planning roads/railway lines, electric lines, pipe lines etc. if the various resistances are quantified with experience and results are used cautiously.

Introduction
From historical point of view, there have been a number of motives for public and private investment in transportation systems. The most important of these have military, political, or economic bases.Ttraditional motivation for establishing transportation systems is to “knit together” the inhabitants of a territory by providing mutual access and communication. More commonly, transportation is thought of as an economic activity, and decisions about transportation systems are motivated by economic concerns. The most basic function of the transportation system is to create what in economic jargon is called time or place utility through the physical transfer of persons or goods from one location to another – in other words, the value of goods depends on where they are and when they are there. Basic economic resources and human population are scattered widely over the face of the earth; in order for a complex economy to exist, raw materials must be extracted, brought together in some form of manufacturing process, and then brought to market. Normally, all steps in this process will require some form of transportation. The commonly used modes of transportation are highways, air, rail, water, pipelines and other modes such as cable and belt systems, ski lifts(James H.Banks,1998). Broadly speaking roads in and adjoining forest areas which are constructed and maintained by the forest department are termed as forest roads. The practice of constructing roads in forest areas is fairly old and the work is carried out by the forest department. The main functions of forest roads are to provide communications in and around forest areas, to serve as a means of transport of forest produce (timber, fuel and other non-wood forest products). The cost of forest products thus depends on the cost of transport which in turn is a function of the distance of the forest from the market and the nature or condition of the road over which it is transported. These roads also help control fire, over exploitation along the main roads/fringes, better patrolling and communications(S.S. Negi, 1994).

Study Area
The kollapur sub division of achampet division comprises of Kollapur and Lingal ranges.The study area of 2308 sq.km.has been selected encompassing the boundaries of the subdivision to facilitate the cost paths to be searched in the neighborhood also(Fig.1). The terrain is complex. It includes level to steep mountainous terrains. The area drains into river Krishna which forms the southern and eastern boundary. The rainfall is deficient which is about 700 mm per annum. In range Kollapur bamboo overlapping working circle with two series with a total area of 20,829 ha. namely Sukkalagundam series of 12,439 Hectares and Medarvote series of 8390 hectares is worked on a felling cycle of 3 years which is prescribed. The system of management is the culm selection system where an individual culm is selected from the clump for felling depending upon its age and congestion in the clump. This system is followed to ensure sustained yield and to prevent deterioration of the crop. The total targets anticipated were not achieved because of non working of the coupes in whole of the areas due to inaccessible areas and no formation of extraction paths (working plan). The projected annual yield from the above two series is about 18 lakh bamboo (4000 MT).


Figure 1
Road alignment in the Hills
The main considerations for hillroad alignments are 1) an extraction road should follow the valleys and should be as near as possible to the lower boundary of the areas being worked. This will facilitate the carriage of timber or other forest produce down to the road head. 2) A main communication road, should as far as possible, follow the ridges. 3) The work of road alignment may be started from the higher obligatory points to the lower obligatory points on either side. 4) Unnecessary ascents and descents are avoided. Every meter of elevation gained is maintained. 5) The slopes may be within the limits of the ruling gradient unless it is absolutely unavoidable. 6) Heavy rock cuts and locations likely to be affected by landslides are avoided. The cost of road construction may also be reduced by detours to avoid deep cuttings and high embankments. 7) Wherever possible, hairpin bends and zigzags are avoided as these are both difficult to construct and maintain. 8) Halting places are provided at regular intervals in long continuously rising roads. 9) It is preferable to align roads on forested slopes than on bare mountain sides; as such alignments are stable and make the roads less costly to maintain. (Krishnasharma.H;1992,&.Negi. SS 1994)

Gradient and its importance
Gradient refers to the longitudinal slope of the center of the roadway. It is usually expressed in terms of the horizontal distance in which the road rises or falls by one unit. It is the degree of elevation or depression of the road surface with reference to the horizontal plane. The terrain is classified as steep terrain, Mountainous terrain, Rolling terrain and level terrain. Steep terrain is a terrain with cross slope greater than 60 per cent. Mountainous terrain is a terrain with cross slope from 25 to 60 percent. Rolling terrain is a terrain with a cross slope varying from 10 to 25%. Level terrain is a terrain with cross slope less than 10 percent. A truck that is capable of handling a load of 3 ton on the level stretch of an earth road can haul on the same gear a load of only 2 tons up a gradient of 1 in 20 and only 1 ton up a gradient of 1 in 10. The effect of gradient is even more on the hard surface of a metalled road. Only half the load can be hauled up on a 1 in 20 gradient as compared with a load on the level surface. The disadvantages of the steep gradient are a) wastage of power b) increased erosion. c) considerable wear and tear of the vehicle. d) more fuel consumption. The different kinds of highway gradients are 1) ruling gradient, 2) limiting gradient, 3) exceptional gradient, 4) minimum gradient (Krishnasharma.H;1992,&.Negi. SS 1994).

Ruling Gradient
It is the desirable upper limit of a gradient. The designer should aim to provide a gradient within the ruling gradient. Mode of transport in the locality will govern the ruling gradients to be adopted. Indian Road Congress (I.R.C.) recommended the limits for plains and hills are 1 in 30(3.3%) and 1 in 20(5%) respectively.

Limiting Gradient
It is the limit of steepest (or maximum) gradient. It is allowed in difficult terrain to reduce earth work. Limiting gradients when used should be separated by flat and easy gradients. I.R.C. suggested the limits for plains and hills are 1 in 20(5%) and 1 in 15(6.66%).

Exceptional Gradients
These are gradients steeper than the limiting gradients which are provided in exceptional cases such as approaches to causeways, near hairpin bends, very difficult terrains to avoid deep cutting. They should be used only in very difficult situation where they cannot be avoided. I.R.C. recommended the exceptional gradients for plains and hills are 1 in 15(6.7%) and 1 in 12(8.3%) respectively. Exceptional gradients should not be adopted for distances greater than 100 m in a stretch of 1.6 km. They should be separated by easy and flat gradients. I.R.C. has recommended gradients according to different terrains.

Minimum Gradient
It is the gradient given to drain away the water longitudinally where there is no sufficient camber. If the side drains are lined it may be taken as 0.5% and if not lined it is taken as 1%.

Methodology
Sufficiently large area has been selected for the study en compassing the forests to search for potential alternatives. The analysis is carried out using Remote Sensing and GIS. Landuse/landcover map for the study area has been prepared using IRS-1D LISS-III data of December, 2000 with necessary groundtruthing.. The reconnaissance survey has been completed at this stage. The bamboo coupes are very near to the southern border i.e. river Krishna. It has been observed that the back waters in the reservoir due to the Srisailam dam are available for most part of the year and can be used for transportation. At Somashila village where a famous temple is present, the river is used by the pilgrims and so the banks are developed for bathing ghats. It is proposed as a depot. Also at Chintapally village there was old depot which is proposed as a depot..The Bamboo coupes are identified and a separate layer prepared. The existing depot at Kollapur is taken as only depot for another analysis. As it is necessary to consider existing roads and their condition, and roads cannot be delineated using RS data in forests due to closed canopy, a road layer has been prepared from SOI toposheet. The contour layer has been prepared using SOI toposheets and a Digital Elevation Model (DEM) is generated. The ordered drains have been delineated using Arc/Info software. The bridges, culverts are identified in SOI toposheet and these are adjusted so as to match the streams on superimposition. The road and stream intersections are also treated as bridges. In all the layers, the cell size is kept 50 m. The proposed road width is taken as 10 m. However as the final cost proportionately varies we can convert to any required width by changing the width proportionately through out length. It means that to traverse a cell vertically/horizontally we need to lay a road of 10x50 sq.m. If the cell is to be traversed diagonally the cost is multiplied by 1.414. In agricultural lands to make provision for the side drains etc. either side 5m extra procurement is proposed (i.e. 20x50 sq.m). From field investigations per hectare costs are obtained (to close approximations) from which the costs to traverse each cell as specified above have been arrived at. These are later divided by cell size to get costs for unit distance (i.e. one meter). For example to clear one hectare dense forest if it costs Rs. 40,000/-and for a cell it costs Rs. 2,000/-and for one meter it cots Rs.40/-. To avoid unnecessary crossing of streams, the costs of constructing culverts/bridges have been estimated stream order wise and assigned to streams. The existing roads have been classified into 4 classes namely metalled, unmetalled, cart track and foot paths. The metalled roads are assigned a cost of 1(lowest), unmetalled roads which require Rs. 50/- for a stretch of 50 m. for minor repairs. The cart tracks are generally 2.5 m wide, it is observed that it reduces expenditure by25% to what it costs otherwise to widen it to 10 m. Therefore it is seen that the cart track takes values (¾) th times the land use present beneath it in RS generated map. The foot paths are not considered at this stage. The water transportation system provides low speed but extremely high capacities. The capital costs of vessels is high but operating costs per ton-mile are extremely low. Environmental impacts are relatively low. Therefore it is given a value of “1”(the lowest). To control frequent switchovers from land to water which involves arrangements for loading/unloading, a barrier is created in edge cells of river throughout its length using AOI tools insuch a way that to cross it the path should atleast horizontally traverse one cell.It is assigned a high value of 5,00,000, (approximate cost of a small crane or development of a small port) except at Somashila village.The broad land use classes obtained from the RS data are further modified using various knowledge components. The roads, streams, bridges/culverts are induced into landuse. To avoid habitations, Waterbodies, rockoutcrops (obligatory points), these have been assigned a very high cost of 1,00,000 per cell. The approximate costs assigned after field investigations to clear/procure are shown in table1.A grid is obtained with these costs (say Weighted LU).Slope map in percentage is generated. As per the guidelines of the IRC; slope weight images for ruling gradient, limiting gradient, and exceptional gradients have been prepared as follows. If the slope of a cell falls in plain or rolling terrain a ruling gradient of 3.3% is advised.

Table1. Cost values assigned to different Land landuse units

Land use	Cost to traverse cell in Rs.	Cost per unit dist. in Rs.
Dense forest	2000	40
Open forest	1000	20
Scrub	500	10
Sparse Scrub	300	6
Agriculture(20x50)m2	6000	120
Habitations	100000	2000
Water bodies	100000	2000
Rock outcrops	100000	2000
Drains(1st order)	5000	100
Drains(2 nd order)	20000	400
Drains(3 rd order)	30000	600
Drains(4,5,6th order)	100000	2000
Bridges/Culverts	1	0
Roads(metalled)	1	0
Roads(unmetalled)	50	1
Roads(cart track)	3/4th of the cost of landuse	(Cost of LU)*3/200
River,Hypothetical Barrier	1, 5,00,000	0; 10,000 respectively

Therefore, for example, to maintain ruling gradient in 20% cross slopes (20/3.3) times normal journey is required, to maintain ruling gradient in steep terrains of 60% cross slopes (60/6)=10 times normal journey is required. Generalizing this we can have Slope weight = [(slope%)/(recommended %)] if it is > 1 & 1 if it is <1.This gives appropriate weight to the slope. This is a multiplicative weight since it multiplies the costs. The weighted LU is multiplied by slope weight of ruling gradient. This is taken as the cell total cost to use in spreading from different source points(A part of the total cost grid is shown in fig2)(Burrough 1980). Similarly the exercise is repeated with limiting gradient exceptional gradient and in combinations.In spreading from a point the backlink and allocation have been obtained.The analysys carried out in two stages with Kollapur depot(existing), and proposed depot(Somashila &Chintapally).The cost surface(Accumulated cost map) spread from Kollapur Depot is shown in Fig.3. The Least cost paths obtained from each coupe to the Kollapur depot draped over DEM are shown in Fig.4(rotated as seen from west). Furthur, a comparison is made between the costs of two different routes available from Chintapally to Bollaram by extracting each path from total cost grid and spreading from Chintapally. To see that the road passes through any obligatory point(bridges, villages etc), it is spread from the obligatory point and least cost paths derived from both ends.


Figure 2

Figure 3

Figure 4
Results and Disscussion
The least cost paths from each coupe to depots, and each cell to depot have been obtained. As the cost path tool optimizes the cost but cannot restrict from passing through gradients not recommended. The paths given cannot be used for alignment straightforwardly. These have to be reexamined to provide suitable gradients using horizontal/vertical curves. The newly aligned paths are much longer than these paths. Here it is assumed that there will not be much local variation in land use in uniformly sloped terrain. The extra weightings given to slopes beyond recommendations will take care of the cost aspect. The path given by the tool can be located using DGPS, taken as a baseline and followed if it is within the recommendations. It has been observed that the path avoided the higher gradients to a maximum extent. Also the drains with higher slopes are exaggerated and so avoided. The natural ports can be taken in to consideration. The results show that out of total length 51% fall in below 1% slope, 31.5% fall in 2-10% slopes, 14% fall in 11-25% slopes and 3.5% fall in above 25% slopes. The new alignment can be started where it is passing through higher slopes and should be joined where it is gaining lower gradients. The paths chose river transport than road transport as river assigned no expenditure. To find access costs of a point the accumulated cost map can be read. The access paths to each point can be generated to lay foot paths by using the accumulated cost as DEM and back link as Flow direction. From the proposed depots it is seen that for the chintapally depot very little area from outside the coupes has been allocated. The results revealed that the cost path tool is highly helpful in planning roads, pipelines, electrical lines, dispersion studies etc.

Acknowledgements
The author is highly grateful to Sri.S.K.Das, IFS; Prl. CCF ,AP; Sri. S.D. Mukherji, IFS; Prl. CCF,AP, (Rtd) for their encouragement. The author is thankful to Sri.K.S.Rao IFS; Addl. Prl.CCF(Admn); Sri.Hitesh Malhotra,IFS; Addl. Prl.CCF(WL); Sri. M.V.S.Prakash Rao;IFS; CCF (IT) ,Sri. S.V.Kumar, IFS; CCF(T&E) , Sri.Tej Singh Kardam,IFS; CF(HRD) for their kind support. The author has gratitude to Sri.A.K.Naik,IFS;Dy.CF(GIS) &Sri.Vivekanandam Dy.CF(T&E) for extending all the facilities and support in conducting this study. The author expresses deep sense of gratitude to all the staff of AP Forest Academy.The thankfully acknowledges Sri.T.Bhashya Karulu FRO,who served in Kollapur for his generous support in providing fielddata.

References

• James.H.Banks –“Introduction to Transportation Engineering”, Mc Graw-Hill International Edition- 1998.
• Negi.S.S,. –“Hand Book of Forest Engineering”, 1994.
• Krishna Sharma.H. Transportation Engineering-1992
• Working Plan for Achampet Forest Division
• Burrough, Peter A; Evans and Rachel A. Mc. Donned – “Principles of GIS”, Oxferd University Press- 1980.