Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2017
Volume 20
Issue 4
Topic:
Forestry
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Goł±b J. , Łuczkowski B. 2017. GIS MAPS AND ANALYSIS IN DESIGNING FOREST ROAD SYSTEM ON MOUNTAINOUS AREAS, EJPAU 20(4), #14.
Available Online: http://www.ejpau.media.pl/volume20/issue4/art-14.html

GIS MAPS AND ANALYSIS IN DESIGNING FOREST ROAD SYSTEM ON MOUNTAINOUS AREAS

Janusz Goł±b, Bogdan Łuczkowski
Department of Forest Engineering, University of Agriculture in Krakow, Poland

 

ABSTRACT

A forest road system is a basic element of a technical infrastructure which enables conducting well-balanced forest management and meeting the postulates of the sustainable environment development. The correct designing of such a system for a specific mountainous forest area is a multi-layer activity, addressing a range of environmental features in the existing and future configuration, including but not limited to: relief, tree stand properties, hydrogeological conditions and a condition of the existing water system. A modern and effective analytical tool for geospatial data is GIS. The Forest Numerical Map Standard (FNM) contains a lot of essential information so that the analyses performed are useful in the road system optimisation.
   This article presents basic analyses conducted against FNM of a specific transportation area (Łopień forest area in Limanowa Forestry Inspectorate, Southern Poland) and the Digital Elevation Model (DEM). By means of QGIS 2.12.0 Lyon, thematic maps were created and basic calculations were carried out concerning: the cataloguing of the existing state, technological typification of tree stands and design of a new road system. These were, among others, the following tree stand analyses: diversification of age, species composition, reserves, quantity and planned timber acquisition. The following was also performed: physiographical analyses concerning exposition and downslope, hydrographic analyses, presence and localisation of nature reserves, building properties of a subsoil, the present condition of the road system and a range of zones of making tree stands available. Furthermore, the operation of tools is presented consisting in filtering the features of elements for their selection, designing the route of new roads in the system with consideration of important properties of the transportation area, drawing a longitudinal profile of the terrain in the place of the designed road, calculating longitudinal slopes of such profiles, visualising road functions in the system on the map and other analyses.

Key words: GIS, forest road system, thematic maps, Forest Numerical Map data analysis.

INTRODUCTION

The functions of forests are outlined in the applicable legal acts [31] but forests must be made available appropriately in order to ensure fulfilling such functions [4, 10, 13, 20, 26]. It is implemented by means of a transport network which is adequately designed, built and maintained. Such a network consists of forest roads of varied functions and bearing capacities, operational and skidding trails and also, to a certain extent, by means of public roads, running inside forest areas (or in their vicinity). It is said that a road system is like a blood circulation system for the forest.

The correct planning of the road system making a forest available is aided by multi-aspect analyses performed based on the standard content of the Forest Numerical Map (FNM) by means of GIS technology [1–3, 11, 12, 15, 16, 19, 30]. It is a modern and simple tool which allows for the selective concentration of lots of critical information simplifying and justifying the localisation of specific road sections [17, 18, 23–25].

Subject: the use of a modern IT technology in designing forest road systems in mountains.

Objective: to present the possibility and purposefulness of the application of GIS tools in forest designing works, including but not limited to designing a road system in forests at the stage of the cataloguing of the existing state and preparing decisions on the localisation of new road sections.

GENERAL DESCRIPTION OF THE STUDY AREA

The said analyses were carried out for "Łopień" forest belonging to Limanowa Forestry Inspectorate (southern Poland), classified as one transport area. This terrain had to be treated integrally because it covers the area around the mountain summit with the same name and it is surrounded by private forests and private pastures and fields. A possibility of accessing public roads is extremely restricted because there are only two such places – in the southern and in the southern-east part of the forest.

Łopień Mountain has three summits with the height of the central summit of 951 m a.s.l. The part of the forest which is situated the lowest has the height of 460 m a.s.l. There are mostly steep, very steep and cliffy mountainsides but in the areas near the ridge the slope is locally very small.

The climate of the region in which the studied transport area is located is pluvial and nival, and affected by the continental climate. An average annual air temperature ranges from 2.8°C for high mountains to 7.4°C for Limanowa and sub-mountainous terrains. Normal precipitation according to Suliński’s formula [29], with summit coordinates N: 49°42’, E: 20°16’, ranges, depending on the altitude, from 840 to 1089 mm. Maximal precipitation is present in summer months and minimum precipitation can be observed in winter months. A snow cover remains from 85 to 140 days. A vegetative period ranges from 160 to 210 days [14, 21, 27].

In geological terms, this terrain belongs to Magurska Nappe which was formed from tertiary sandstone, slates and marls and to a smaller extent from cretaceous slates and sandstone [28].

The system of factors described determines the conditions for building and using roads in this terrain.

METHODOLOGY

The analyses presented provide information necessary for planning forest road systems in mountains according to the methodology applied in the National Forest Management “National Forests” (NF) but only at stages which are currently implemented as part of the “Expert reports on the optimisation and development of road infrastructure” for forestry inspectorates [6]. These are as follows: a stage of cataloguing the forest condition and recent road system, stage of technological typification of tree stands and a stage of localising new roads in the system. Gołąb and Plewniak [8] wrote about difficulties in the application of the methodology which has been used for 50 years. A partial loss of relevance was a consequence of the change in the principles of the forestry inspectorates functioning after political changes in Poland in the nineties of the previous century. At the same time, a powerful technological development supplied tools for the multi-aspect analysis of data included in the standard Forest Numerical Map (FNM). A highly efficient and popular tool is GIS programming. All the analyses and maps are prepared based on internal programme procedures QGIS 2.12.0-Lyon [7] and a few generally accessible sub-programmes functioning on this platform – “plugs-in”.

The data source is the Forest Arrangement Plan for the years 1 I 2006 to 31 XII 2015 for Limanowa Forestry Inspectorate [21] and the Digital Elevation Model (DEM) for this area.

THE APPLICATION OF GIS AT THE STAGE OF CATALOGUING THE CONDITION OF THE ROAD SYSTEM AND TREE STANDS

The cataloguing of the condition of the recent road system covers the description of the functions of respective roads, their categories, surface types, bearing capacity, length and width of road sections, contact points with public roads, load streams, and collecting essential information on tree stands.

There are some analyses presented below in the form of thematic maps describing: species composition, tree stand age, large timber distribution, localisation of roads and skidding trails, terrain exposition, slopes, zones of making tree stands available from roads with a specific skidding system (according to FNM and DEM).

In Figure 1 there is a species description of tree stands presented by indicating major species. Figure 2 presents an analysis of an average age of tree stands in twenty years’ classes.

Fig. 1. Major species in the tree stands of the transport area

Fig. 2. Age diversification of tree stands

The above analyses are carried out based on the information contained in the table of attributes of a layer describing respective tree stands in allocations.

The map below (Fig. 3.) demonstrates the route of roads and skidding trails in the terrain according to the classification and description in respective FNM layers.

Fig. 3. Existing transport routes

If the table of attributes of a layer containing information on roads does not contain all required data, it is necessary to complete such information based on one’s own site inspection, so that the map analyses performed are complete and reliable (road category, surface type and the function of respective roads in the system).

Fig. 4. Terrain exposition

Figure 4 presents the analysis of a terrain layer, which is directing slope lines in relation to the cardinal points. The analysis described uses DEM with 10m pixel. The mountainside exhibition is significant for the formation of thermal and humidity conditions on a given terrain, which, in turn, affects the bearing capacity of the bodies of roads on such areas.

Figure 5 presents the analysis of the downslope in DEM with 10 m pixel. A downslope determines, to a great extent, the management conditions and also the possibilities and costs of road building and maintenance.

Fig. 5. Downslopes

The road system description requires to calculate basic descriptive coefficients. These are as follows: road system density index (g) and average distance between roads (b). In order to calculate these coefficients (at this stage they will refer to the existing system), it is possible to use a programme function which calculates basic statistical parameters for specific layers – we read a cumulative length of all the existing roads and cumulative forest area. In Figure 6 There are both sub-programme tables with statistics (separate analyses). The units in which these values are presented are determined in the global design settings. In this case length is determined in metres and area in square metres.

Fig. 6. Tables with statistics for the length analyses of the existing roads and branch areas

Road system density (g), one of the fundamental parameters describing the system, is calculated according to the following formula (1):

      (1)

where:   
L   – forest roads length [m]
PL
– forest area [ha]

Based on the road system density index (g), it is possible to calculate another crucial parameter – an average distance between roads (b, according to formula 2):

      (2)

where:   
g   – road system density index [m·ha-1]

In Figure 7 there is presented the first stage of assigning the zones ranges of providing access to tree stands. The width of such zones is determined by the existing skidding technology. There is a procedure of creating buffers with a specific width for selected linear elements (forest roads existing in the road system). At further stages, the size of such buffers is modified because skidding routes must avoid protected elements, foreign creeks and enclaves and uphill skidding.

Fig. 7. The first stage of indicating the zones of providing access to tree stands from the existing roads

THE APPLICATION OF GIS AT THE STAGE OF THE TECHNOLOGICAL TYPIFICATION OF TREE STANDS

At this stage of designing a forest road system the following is determined: a skidding technology and skidding measure types based on an average downslope on the transport area. On the basis of DEM it is possible to generate statistics concerning downslopes (including an average value) based on the map pixel. Below there are the results of such two calculations for DEM with a different pixel value – 20 m and 1 m, which affects the accuracy of the results obtained. Since the entirety of the available DEM extract is much larger than the transport area, the calculation scope must be limited by means of the ‘external boundary’ layer. The values of the statistics are saved by the programme in the table of attributes of the applied limiting layer (Fig. 8 and 9).

Fig. 8. Table of attributes of the ‘external boundary’ layer with statistics for downslopes (20m pixel)

Fig. 9. Table of attributes of the ‘external boundary’ layer with statistics for downslopes (1m pixel)

Average downslope with the use of DEM:

With a determined average downslope, it is possible to define the techniques and measures for skidding according to Table 1.:

Table 1. Recommended skidding technologies and measures depending on the average downslope for the Polish conditions (source: [22])
inclination [°]
skidding types (skidding technical measures)
0–10
skidding by tractors or specialist tractors, horses
11–20
skidding by light and average (power) specialist tractors, gravitational, horses
21–30
skidding by cable railways (hoisting winch), horses
> 30
skidding by cable railways (cranes)

THE APPLICATION OF GIS AT THE STAGE OF LOCALISING CORRIDORS OF NEW ROADS IN THE SYSTEM

Corridors must be understood as the initial indication of the course of new roads in the terrain. Such localisations are recommended for the correct functioning of a future road system, and detailed road designs in such corridors will be created later on in a separate design process.

While commencing the road system optimisation, it is necessary to localise points on the transport area classified in the following three categories: points (or area elements): “negative”, “critical” and “positive”.

“Negative” points are points which must be avoided and there must not be roads in such points or in their immediate vicinity. These include: foreign enclaves (other owners), areas valuable in terms of nature or elements under legal protection (reserves, natural monuments, nesting zones of rare species of birds, animal lairs, documented stands of extremely rare species of plants). The said map is presented in Figure 10. For point elements, protective zones must be presented by means of the ‘buffer’ tool.

Fig. 10. Distribution of the nature protection elements on the transport area

“Critical areas” are places in which roads may be problematic or dangerous both for the environment and for the road itself. This category includes very steep terrains, creeks and their springs, and soils which due to their particle size are not adequate for building purposes [9]. Building roads in such conditions may evoke uncontrolled mass movements (land-sliding) and changes in the local hydrological system; on the other hand, the building process and subsequent road maintenance will be more difficult and more expensive and the bearing capacity of the road body and surface will be low. One of the reasons are extensive earthworks which will change the mountainside statics. Yet another reason is using necessary advanced de-watering systems, collecting water from the road and discharging it in points and in a concentrated form on the mountainside. Dewatering systems require proper technologies and materials and frequent supervision, at the same time without a guarantee of the correct de-watering of forest road bodies in all weather conditions. It is advisable to note the synergic operation of a few critical factors occurring in the terrain simultaneously. The respective maps are presented in the following Figures: 11, 12 and 13.

Fig. 11. Downslope analysis – distribution boundary 20 degrees

Fig. 12. Hydrographical network of the transport area – creeks, springs and their protective zones

Fig. 13. Technical conditions for road building – combined analysis of downslopes, hydrographical zone and soil type

“Positive” points are places in the terrain which should be made available by means of a road system after its optimisation. A main objective of the existence of roads in production forests  is a possibility of transport means reaching specific tree stands. Access urgency is determined based on the planned timber acquisition specified in the current Forest Arrangement Plan (FAP) and anticipated timber acquisition in the forthcoming decades (based on the tree stand growth rate theory). The forest fire protection is not without meaning here. It may be performed by analysing tree stands in terms of their age, quantity and planned cutting sites, and adjustment of the existing species composition to the managed tree stand type (MTST) specified in FAP. If the species composition is not consistent with the recommended MTST, such tree stands will be transformed, providing a higher timber acquisition rate. The described failure to adjust the species composition to the recommended MTST can be observed in mountain forests  frequently as spruce tree stands cultivated in habitats with a higher fertility rate than the requirements of this species. Fire recommendations define a maximal distance of an arbitrary place in the forest from roads which are used to reach a site on fire.

A map based of which it is possible to analyse the distribution of tree stands of a specific age is provided in Figure 2. (performed at the stage of cataloguing the current condition of the forest), and the remaining thematic maps including information on reserves, quantity, spruce share, size of planned cutting are provided in Figure 14–17. The anti-fire access to tree stands may be specified by the use of the “buffer” sub-programme but such an analysis is carried out in forests with a high fire risk.

Fig. 14. Timber reserves in given branches

Fig. 15. Quantity of tree stands

Fig. 16. Percentage share of a spruce in the species composition of tree stands

Fig. 17. Anticipated timber acquisition in a decade – according to the valid FAP

Figure 18 presents the ‘filter’ sub-programme window by means of which it is possible to select complex and detailed information. This example includes conditions enabling the presentation of the localisation of tree stands where spruce share is higher than 50%, an average age of a tree stand exceeds 50 years and the tree stand quantity is lower than 100m3∙ha-1. The logical operator ‘AND’ results in indicating tree stands which satisfy all three conditions simultaneously. Figure 19 presents the localisation of tree stands which satisfies the conditions of such a filter.

Fig. 18. Dialogue window of ‘filter’ tool for conditional information selection

Fig. 19. Map presenting tree stands satisfying the filter conditions from Figure 18

Figure 20. presents the proposal of the road corridors localisation in a new road system against the points and areas from the following categories: “negative” and “critical”. The relief as well as the existence and spatial distribution of negative and critical points and areas is sometimes so complicated that the consideration of such all conditions simultaneously is not feasible. Therefore, a final shape of the designed road system depends on the professionalism and responsibility of a designer.

Fig. 20. Proposed road system against “negative” and “critical” areas

Fig. 21. Proposed road system against tree stands satisfying the filter conditions from Figure 18

Figure 21 presents the localisation of roads in a new road system against tree stands selected by means of the filter shown in Figure 18

A road system design ought to be characteristic for, among others, a prospective possibility of implementation. It is important that roads allocated along corridors indicated in the design reach parameters included in the ranges acceptable in technical standards. One of the fundamental road parameters is a gradeline – the designed corridor arrangements must enable designing a route so that a gradeline does not exceed the set maximum values. GIS system indirectly provides a possibility of determining terrain inclination in the designed corridors by means of DEM. It is necessary to use the ‘terrain profile’ sub-programme which draws longitudinal terrain profiles in corridors, based on which it is possible to control slopes. If a downslope is exceeded (Fig. 24.), and it cannot be compensated by earthworks to a reasonable extent, it is necessary to suggest a different corridor route.

Below, in Fig. 22 and 23, there is a sub-programme window and a longitudinal corridor profile with a working number 103, made by means of DEM with 1m pixel and an extract of a table with data to draw the above profile (distances and heights).

Fig. 22. A window with a terrain longitudinal profile for the corridor of road No 103

Fig. 23. Table of a terrain longitudinal profile for corridor No 103 containing point distances and heights

Table 2 includes downslope sizes calculated by means of Excel for corridor No 103 (for an initial section with the approximate length of 25 m). The output numerical data were copied from the table provided in Figure 23.

Table 2. Downslopes of the initial section of corridor No 103
distance from the beginning
height of point
section length
height difference
slope in section
[m]
[m]
[m]
[m]
[%]
0,000
763,297
1,204
0,054
4,49
1,204
763,351
1,204
0,188
15,61
2,408
763,539
1,204
0,188
15,61
3,613
763,727
1,204
0,065
5,41
4,817
763,792
1,204
0,200
16,61
6,021
763,992
1,204
0,200
16,61
7,225
764,192
1,204
0,066
5,48
8,429
764,258
1,204
0,236
19,60
9,634
764,494
1,204
0,250
20,76
10,838
764,744
1,204
0,091
7,56
12,042
764,835
1,204
0,250
20,76
13,246
765,085
1,204
0,250
20,76
14,450
765,335
1,204
0,091
7,56
15,655
765,426
1,204
0,192
15,97
16,859
765,618
1,204
0,188
15,61
18,063
765,806
1,204
0,029
2,41
19,267
765,835
1,204
0,188
15,61
20,471
766,023
1,204
0,188
15,61
21,676
766,211
1,204
0,029
2,41
22,880
766,240
1,204
0,200
16,57
24,084
766,440
1,204
0,204
16,94
25,288
766,644
slope in the average:
13,24
slope in the maximum:
20,76
slope in the minimum:
2,41

Figure 24 presents a manual method for specifying a downslope in corridor No 104, for a section in which significant exceeding of permissible inclination is anticipated.

Fig. 24. Manual method for the determination of a longitudinal downslope for the part of corridor No 104

Figure 25 presents the functions of road sections in the design of an optimised road system. The decisions on functions are reflected in the anticipated traffic rate, road parameters and distribution of a timber terminal.

Fig. 25. Functions of respective road sections in the optimised road system

Fig. 26. A table with basic statistics for a layer containing all the roads in the optimised road system

Figure 26 includes an output sub-programme window providing basic statistics for all the roads in a new, optimised road system. On the basis of the sum of the length of all the roads and a forest area of the transport space (as at the cataloguing stage), a density index of the designed road system is calculated as well as an average distance between roads in their new system (formula 3 and 4).

Forest roads length (L):          24 237.44 m
Forest area (PL):         691.19 ha (unchanged)

      (3)

      (4)

Denomination as in formula 1 and 2.

Figure 27 presents the access zones of tree stands from all the roads after the road system optimisation according to the accepted skidding technology.

Fig. 27. Providing access to tree stands by means of a new road system according to the accepted skidding technology

By using ‘Qgis2threejs’ sub-programme (with a repository) it is possible to perform a 3D visualisation of the developed transport area and designed road system. A user may choose visible elements, zoom in and rotate a view.

Fig. 28. 3D visualisation of the transport area from the north

CONCLUSIONS

GIS technology, as a standard of analysing and developing spatial environmental data, is also applied in the process of the optimisation of forest road systems. Designers must consider  a lot of economic and environmental aspects so that the access to the forest is as good as possible, with environmental costs at the lowest level [4, 10–13, 16]. Therefore, a detailed analysis includes the existing condition of the prepared transport area which orders the information and determines an initial condition of the forest as a whole [17]. Information on the relief, hydrogeological conditions, tree stands and shape and conditions of road systems is very interesting. In order to design the course of corridors correctly, it is necessary to indicate places and areas which are determined as “negative”, “critical” and “positive”. According to the authors, what is most difficult here is to adjust the course of corridors to the relief in order to achieve the permissible longitudinal inclination of designed roads. A solution here can be a sub-programme (a plug-in) which would aid marking the line of a constant slope. The programme used by the authors (Open Source) lacks such a plug-in in the official repository. Hence, it is required to perform the additional control of the size of longitudinal slopes for the designed corridors.

In the road system design presented above, the achieved road system density index, untypically for the Polish mountainous conditions, is relatively high [5]. It may be stated that it is a maximum variant and a necessity must be considered for building roads in all the designed localisations and correcting the course of some corridors (e.g. corridor No 104, Fig. 24). Additionally, based on a harvesting size and removal urgency (Fig. 17 and 19), one must decide on the sequence of building sections, distributing building costs into a few or several years. Firstly, main removal roads and depots must be created, and then some side roads will be built.

It must be noted that it is crucial to hold an updated and correct map (FNM) and DEM with a proper raster size because the quality of such materials determines a suitability value of the analyses conducted.

The analyses discussed in this study exceed the economic criteria of the optimisation of road systems in forests which have been applied so far and it is an unquestionable asset. Nevertheless, there are no clear and suitable criteria for determining an optimal road system density in the specific conditions of the transport area. There is also a lack of any set of analyses which is, in fact, obligatory while performing a design of the optimisation of forest road systems in mountains.

Conclusions

It is necessary to select and describe updated criteria for determining the optimal density of the forest road system.

Acknowledgements

This work was financed by the Department of Forest Engineering University of Agriculture in Kraków.

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Accepted for print: 30.12.2017


Janusz Goł±b
Department of Forest Engineering, University of Agriculture in Krakow, Poland
al. 29-listopada 46
31-425 Kraków
Poland

email: rlgolab@cyf-kr.edu.pl

Bogdan Łuczkowski
Department of Forest Engineering, University of Agriculture in Krakow, Poland
al. 29-listopada 46
31-425 Kraków
Poland

email: bogdanluczkowski88@gmail.com

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.