Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
Using CIS to site the Beirut-South mountain
highway
(SMH)
S. Sadek, I. Kaysi & M. Bedran
Department of Civil and Environmental Engineering
American University of Beirut, Beirut, Lebanon
Email: salah@aub. edu. Ib
Abstract
Lebanon is emerging from a very destructive 15-year long period of civil strife.
As the reconstruction effort of the devastated Lebanese infrastructure intensifies,
new roads and highways are being studied, designed and making their way
towards execution. One of the most critical traffic concerns is associated with the
Southern entrance to the capital, Beirut. A number of solutions are envisaged.
They include the provision for a mountain highway linking the Khaldeh area at
the southern outskirts of Beirut, to the town of Damour 12km to the South. A
CIS decision-aid platform developed by the authors was used to establish the
optimal alignment for the proposed Beirut-South Mountain Highway (SMH).
Results of this case study demonstrate the advantages of the use of GIS in
highway siting applications. The SMH application addresses the potential of GIS
platforms in providing a quick and very useful insight into optimal alignments for
highways.
1
Introduction
None of the major elements of Lebanon's infrastructure survived the
fifteen year long civil war. The damage ranged from total destruction to
extreme deterioration due to the lack of maintenance and upgrade. As the
damage was assessed, and the needs evaluated at the end of the war, it
was clear that the reconstruction and rehabilitation task would be a very
long and costly undertaking.
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
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GIS Technologies and their Environmental Applications
The transportation infrastructure was extensively affected. Existing
highways, bridges and roads needed immediate rehabilitation and
improvement. Furthermore, the mass movements due to the Lebanon
conflict, and the resulting population redistribution, necessitated that new
services (roads, electricity, water and wastewater networks) be extended
to war-era developments.
It is expected that the bill for the rehabilitation and upgrade of the
roads and highways network alone, will run into the billions of US
dollars over the next decade.
One of the major challenges facing planners and engineers is to
address the traffic congestion that has reached unmanageable levels at
the northern and southern entrances to the capital city, Beirut. The
problems are particularly acute at the Southern entrance to the city.
Historically, that area suffered from very high traffic congestion that predates the war years. In addition, very dense new developments have been
constructed as the city expanded into its suburbs, and a number of major
projects, including an extension of the Beirut International Airport, are
under construction. In order to address the needs of the Southern
entrance to Beirut, a number of solutions are under study, some of which
are already being implemented. A total overhaul and upgrade of the
existing coastal highway has been completed, and a new highway linking
the area of Khaide at the outskirts of the city, and the town of Damour,
12 Km to the South, is in the design stage. This new highway, the
Beirut-South Mountain Highway (SMH), will link the two localities
through the coastal mountains.
The work described in this paper involves the application of a GIS
framework to the selection of the final alignment for the SMH. The use
of GIS in the transportation field is on the rise and the number of
potential applications being developed is growing at an ever-increasing
rate (Vanderhoe et al.[l], Stokes & Maucci [2] Aifandopoulou et al. [3],
and Zura et al. [4]).
2
Traffic analysis
The South Mountain Highway (SMH) is being proposed as a relief axis
for the existing coastal highway. It is considered as an intrinsic part of
the peripheral highway system for the Beirut Metropolitan Region
(BMR). Sections of the peripheral highway system are under design and
other are already in the construction stage.
An in-depth traffic analysis was conducted for the SMH (ACE [5]).
The analysis horizon was taken as 20 years, up to the year 2015. A
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
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189
computer-based regional transportation model was used as the basis for
the traffic analysis. The projected trip interchange matrix for the BMR at
year 2015 was used, and all existing and planned new highways and
roads up to that year were taken into consideration.
The traffic analysis demonstrated the critical need for the SMH
relief axis. The most effective start and end points for the SMH were
established (Figure 2), along with the areas served, and the number of
lanes required for different sections of the proposed SMH highway.
These constituted the starting elements in the alignment selection
process, in which GIS was introduced.
3
Siting / alignment requirements
At this stage of the design, only the points of origin and destination were
fixed. The traffic analysis implied requirements as to the areas to be
served, along with the preliminary number of lanes in different zones.
Further constraints were established:
• Avoid heavily constructed areas.
• Avoid intercepting already existing structures
• Whenever an existing road is intersected, a minimum clearance of
6m should be provided.
• A maximum desirable grade of 6% is set for the vertical alignment.
• Avoid problem soils and adverse geologic strata if possible.
3.1 Evaluation criteria
The above requirements were grouped into four categories:
environmental, community disruption, geometric, and geotechnical
criteria.
3.1.1 Environmental criterion
In the case study introduced in this paper, noise exposure due to the
presence of the proposed highway was the only environmental impact
considered. The noise exposure was taken to be directly related to the
number of structures within a 150m distance from the edge of the
highway.
3.1.2 Community disruption criterion
This criterion is defined as the number of structures hit by the highway
itself (actual width) plus a 10m band either side of the edge of the
highway.
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
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GIS Technologies and their Environmental Applications
3.1.3 Geometric Criteria
• Horizontal alignment The number of horizontal curves with radii
less than 200m is taken as a criterion is this case. These curves may
constrain the 80 KM/hr design speed.
• Vertical alignment The cumulative length of route segments with
slopes falling in one of three categories, is established as the
criterion: below 5%, between 5-8%, and greater than 8%.
• Total length of route The total length of the alignment is set as an
evaluation criterion.
• Potential number of road structures Critical stations, where the
cut depth orfillheight is greater than 10m, are identified. The value
of 10m was selected as a point beyond which consideration should be
given for possible road structures, which would affect the final cost
and desirability of the alignment.
3.1.4 Geotechnical criteria
• Earthworks and type of material
The criteria are the total
cumulative volumes of cut and fill, according to the various
soils/geological strata. The type of material to be excavated can have
a direct impact on the cost associated with the route alternative.
Furthermore, the knowledge of the type of soil over which filling is
to be done has significant cost and feasibility implications.
• Slope stability In this case the number of critical sections/stations
from a slope stability consideration is set as the criterion:
Number of sections with Factors of Safety, F.S.<1.0
Number of sections with 1.0<F.S.<1.5
Number of sections with F.S.>1.5
4 GIS
Region
model
for the Beirut
Metropolitan
GIS was used in order to produce an efficient approach for evaluating
various route alignments for the SMH with reference to the criteria set in
section 3. In order to do that, a geographically referenced model of the
Beirut Metropolitan Region (BMR) was developed to include all the
necessary coverages (Bedran [6]).
The BMR is the largest urban center in Lebanon (Figures 1&2). It
covers an area of approximately 230 km^. Building the model for the
BMR involved:
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
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•
Assembling the following available coverages for the BMR: Roads,
Rivers, Cities, Towns, Villages, Land-Cover, Land-Use and Existing
roads and structures.
• Building the following coverages from various "hard-copy " sources:
geology, soil, faults, depth to water table, and topography.
• Assigning preliminary geotechnical properties to the different
soils and geology formations
This was a very time consuming and challenging task, given the
absence of consistent, up-to-date information and hard copy maps to
proper scale.
5
SMH
Alignment analyses and evaluation
The analysis of three of the potential route alignments is described in the
following section. These potential alignments are shown in Figure-3.
SMH-A2 is a low elevation/altitude route, SMH is a medium altitude
route and SMH-A1 is a "high" elevation option.
Meeting all the specified criteria in one optimal solution is a
challenging task that is traditionally performed in separate stages. With
the use of the GIS platform developed by the authors, the various stages
were all merged in to one. As such, many alignments could be tested in a
very short time period with minimal effort. The results are automatically
produced in an easy to evaluate format consisting of cut and fill volumes
summary by soil and geology type (Figure-3), vertical alignment profile
(Figure-4), and a slope stability summary plot by stations analyzed
(Figure-5). At each station, a cross-section is generated, showing the
original Natural Ground Line (NGL) and the Proposed Ground Line
(PGL) (Figure-6). Typical results of the slope stability analyses
conducted within the GIS platform are shown in Figure-7 for a section of
alignment SMH-A1.
Table 1 is a summary of the reports for the three alignments based
on the multi-criteria set. A quick reading of Table-1 shows that the
higher elevation option SMH-A1 affects a lower number of structures
(actually hit structures and structures affected by noise pollution). This
option however, involves larger cut and fill volumes, more slope stability
concerns (Figure 6), and longer cumulative highway lengths with high
gradients, the potential need for more road structures, and a longer total
route length than either SMH or SMH-A2.
The SMH-A2 test alignment on the other hand, tends to present
fewer stability and potential road structures concerns, however, given its
proximity to the densely populated coastal strip, it tends to intersect more
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
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GIS Technologies and their Environmental Applications
existing structures and roads, and has significant noise and
environmental impacts.
Finally, the SMH alignment appears to be the better option given the
criteria set. It intersects the lower contour elevations, bypasses the
heavily populated areas, with minor community disruption and noise
impact.
Table 1. Summary of the results for alternatives SMH, SMH-A1
and SMH-A2
CRITERIA
SMH-A2
SMH
SMH-A1
13
12
1
315
102
65
6
7
7
12053m
0
0
12053m
9
11405m
1268m
8030m
4182 m
1428 m
1364( )m
12
Community Disruption:
Number of structures within
road width + 10m
Environmental Issues- Noise:
Number of structures within
edge of road + 150m
Geometric Design Issues :
• No. of horizontal curves with
radii < 200m
• Cumulative length of route with
0-5% slope
5-8% slope
>8%
• Total route length
• Potential # of Road Structures
6
12673 m
9
Conclusions
GIS based platforms are increasingly being developed to tackle various
civil engineering design and analysis tasks, which have traditionally been
very tedious and time consuming.
The application presented in this paper is concerned with the task of
selecting optimum effective alignments for proposed highways, in
accordance with a large set of competing criteria. These criteria are
varied and they range from environmental to geometric and geotechnical
considerations, among others.
The case of the SMH demonstrates the advantages of incorporating
GIS in the evaluation/decision making process. Such undertaking is not
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
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193
always an easy task, particularly in developing nations, where the paucity
of data is a real and, at times, daunting challenge that has to be met and
overcome.
Acknowledgments
The support of the University Research Board of the American
University of Beirut is sincerely acknowledged, along with the technical
assistance and support of Khatib and Alami Consulting Engineers, and
ACE Consultants, Beirut.
References
[1]
Vanderohe, A. P., Travis, L., Smith, R.L., & Tsai, V.,
Adaptation
of geographic
information
systems
for
transportation, NCHRP report 359, Transportation research
board, Washington, D.C, 1993.
[2]
Stokes, R.W., & Marucci, G., GIS for transportation: current
practices, problems and prospects, ITEJ., 65(3), pp. 28-37, 1995.
[3]
Aifandopoulou, G., Nathanail, T., & Panayotakopoulos, D.,
ETIS: a GIS technology based "tool" for supporting strategic
environmentally friendly planning of urban transport
infrastructure development. Proc. of the 15th environmental
systems research institute (ESRI) user conference, 1995.
[4]
Zura, M. & Lipar, P., The road and traffic environmental
impact assessment and optimal road layout selection, Proc. of
the 15th annual environmental systems research institute (ESRI)
user conference, 1995.
[5]
Associated Consulting Engineers (ACE), Conceptual design of the
South Mountain Highway, Draft Report submitted to the Lebanese
Council for Development and Reconstruction (CDR), March 1997.
[6]
Bedran, M., A geographically referenced model of the Beirut
metropolitan region (BMR) incorporating pertinent geotechnical
properties, MS Dissertation, Dept. of Civ. and Env. Engrg.,
American University of Beirut, Beirut, Lebanon, 1997.
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GIS Technologies and their Environmental Applications
HIGHWAY PROFILE
Figure 4: SMH
vertical alignment
Figure 5: Stations of slope stability concern
Alignment SMH
Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517
GIS Technologies and their Environmental Applications
-50.00
-10.00
-30.00
-20.00
-10(10
0.00 10.00 20.00
Offset (111)
30.00
Figure 6: Highway section at station 2+100
197
1000 50.00
(SMH)
95 _,
85
<UCD 75 .
X
< 65 _
I
15
25
35
45
55
X-AXIS (feel)
65
75
Figure 7: Results of slope stability analysis
Critical failure surfaces section 1 + 100 (SMH-A1)
85