K.P.Wagley
Senior Consulting Engineer
(Bridge)

Background/Abstract

Scientific evidence suggests that adopting the climate change is among the biggest challenges humanity may face in the coming years. It is believed that the increasing atmospheric concentration of Co2 and other gases like CH4 and N2o etc. released by human activities are warming the earth by a mechanism commonly known as “Greenhouse Effect” or (Global Warming). In other words: Global Warming (GW) is a change in average weather of the earth measured by Temperature, Precipitation and Change in Wind Patterns and Storms. Road transport & other hard-engineering infrastructures sectors are a key area that contributes Global Warming by greenhouse emission. This gives more justification of a need for proper planning of the engineering infrastructures to ensure that resources used optimally.

The main focus of adaptation strategies to reduce climate hazards has been on hard-engineering infrastructures such as roads and bridges, seawalls, irrigation structures and hydro-power etc. Closer attention to a broader spectrum of adaptation option seems urgently needed and accordingly, this paper is mainly focused on the Environmental Impact due to Global Warming on Transportation Infrastructures.

Key Words:

Global warming (GW), transportation, climate, emission, engineering infrastructures, adaptation, environment, weather etc.

Introduction

The climate change, the GW and their consequences have already experienced since few years back. Globally the mercury is already up more than 1.20 C and even more in the sensitive Polar Region and in the high altitude of Himalayan Mountains. Signs are appearing all over the world including Nepal and some are surprising. The heat is not only melting glaciers and sea ice, it is also shifting precipitation patterns and setting animals on the move & other effect could happen later this century if warming continues. Based on the climate-science literature and other research works, it can be concluded that the next 50 – 100 years the following specific impact of GW will have potentially serious implications on the Global Environment including human being, plants, animals as well as the man made Engineering Infrastructures.

The consequences experienced in the last few years include:

• Researcher Bill Fraser has tracked the decline of Penguins on Antarctica, where their numbers has fallen from 32000 breeding pairs to 11,000 in 30-years
• Some butterflies, foxes and Alpine plants are moving further north or higher or cooler areas adopting as per their need
• Early flowering of plants in Nepal (Laliguras is flowering in the month of February against the anticipated time of March)
• Ice is melting especially in the Polar Regions. This include mountain glacier and in the high Himalayan Ranges of Nepal resulting rock avalanches, drifting of snow, GLOF, river flooding etc. with the loss of lives & property
• Sea level rise became faster over the years – threatening the island countries from submergence
• Precipitation (snow and rainfall) pattern has been changed globally
• Hurricane and other are likely to become stronger than past threatening the people in the coastal areas.
• Floods and draughts have become more common
• If the ice cap continues to melt at its current rate, the people who rely on it for drinking purposes & Hydro-power Projects will be without source on either.
• Environmental pollution is increasing rapidly in the city areas globally by the increase in intensity and frequencies of the transportation system

Due to GW, we in Nepal facing increasing problems relating to premature damage to transportation infrastructures like roads and bridges as a result of landslides, intense and prolonged precipitation events, rapid sediment deposition and increase in the frequency of historically low return period floods. Apart from landslides and erosion, the Himalayan region of Nepal is quite susceptible to disastrous hazard due to Glacier Lake Outburst Flood (GLOF).

Recent focus of problem on GW is drawing worldwide attention to find out the effective way to reducing the emission of Greenhouse gases. A large amount of natural resources are consumed in commissioning hard-engineering infrastructures and hence the need of proper planning of the engineering structure to ensure that the resources used optimally. The problem climate change on engineering science is very wide and complex as such the paper will mainly focus on Impacts of Global Warming on Transportation Infrastructures.

Possible Future Impact of Global Warming in Transportation Infrastructures

Climate

Phenomena

Global Impact

Possible Impacts

Impact on Transportation infrastructure

Temperature

Rise (very likely)

Burning of fuel and fossils in construction industries

Increase in traffic in transportation sector

Increased Heat stress

(Temperature rise)

Increased heat stress

Increased heat stress

Melting of ice:

Increase of water in glacier lake –

Possibility of GLOF/drifting snow/avalanches in glacial & periglacial regions;

Melting of ice in high Himalayan:

Expansion & contraction of bridge joints

Generation of heat means – more evolution of Co2

More evolution of Greenhouse gases

Evolution of G-H gases;

Lowering of Ground water Table;

Increase risk in Roads, Bridges, Hydropower and other built structure along the river banks with loss of lives & property. On August 26th 2026 big disaster ever in the history mankind in Nepal. A devastating flood hit Bhote Koshi river and its corridor from Timure via Betrabati, Trishuli and its corridor up to Chitwan causing loss of lives of more than 7 thousand people, washout of several roads and bridges, washout of thousands of residential buildings, hydropower projects & washout of the thousands hecters of cultivated lands along the river corridor at D/S. Total loss of properties exceeds above10-Kharab (NRs 387.5 billion) and more.

Note: Estimated average velocity of flow during disaster- 80 km/hr & height of flow: 10 – 15 m from the rive bed depending upon the bed slope.

Scarcity of drinking water sources and Reduction of water sources for hydropower projects

Causes damages to expansion joints;

Deformation of steel members of steel bridges; Shearing of bolts in steel truss bridges; Fatigue cracks in steel structure.

Buckling of rail track and shearing of the joint bolts

Accelerates the carbonation process in re-bars resulting cracks in RCC structures

Rapid degradation of road and runway pavement especially the asphalt

Excessive environmental pollution & increase rate of GW

Traffic jam in at the intersections in the city areas world-wide;

Increase rate of G-W

Problem in foundation of structure;

Scarcity of ground water resulting dryness and draughts

More Intense Precipitation Events(very likely)

Change in precipitation pattern

Increased risk of landslides; Erosion, River flooding, River incision, Debris flows including boulder

• Damage and washout roads, bridges, hydropower projects; washout of the structures along the river banks;
• Scouring of support, siltation of riverbeds; overtopping and washout of roads and bridge approaches etc.

High water table in lakes & rivers

Changing of GWT; heavy abrupt snow drift

Burry of bridge structure;

Change in flood frequency analysis;

Formation of temporary dams & abrupt flood;

Risk to bridge protection work/ river protection works

Increased Asian Monsoon

(Variability likely)

Increased floods and drought magnitude;

1in 50 year precipitation events could be decadal in 2050

Change in approach to road and bridge design and construction;

May require change in design code and practice;

Risk to associated structure

Increased Incidents of severity of storms

Increased heat stress

Possibility of Hurricane and cyclones

Possibility of bridge washout in coastal areas;

Katrina Hurricane is a burning example;

Collapse of Minneapolis Bridge in St. Louis;

Collapse of Tacoma Narrow suspension Bridge in 1940; Uprooting of trees and damages of the structures by strong wind;

In Nepal there are several cases of false-work failure of bridge, fall of the steel truss structure by the strong wind etc.

More than 80% of the country’s territory is occupied by hills and mountains. In the mountainous topography instability of slope is ever present hazard, and rain water/precipitation is always instrumental to cause slope failure. Beside this, since last 30-years Nepal is facing increasing problems relating to premature damages of Roads, bridges and other associated transportation engineering infrastructures as a result of frequent GLOF and river flooding, debris and mudflows, erosion and landslide, river incision, periodic seismicity etc.

Possible Future Impacts of Global Warning/Climate change in Nepal Context

The three parameters of GW that are closely related to the context of Nepal are:

• Temperature rise/Heat waves –Signs are showing that high temperature and heat waves are likely to become more intense and more frequent and last longer than they do today.
• Change in precipitation/rainfall pattern – Since last 30-years, there has been significant increase in frequency and intensity of heavy precipitation causing premature failure of roads and bridges and other associated structures. Recent (end of October 2021) unseasoned heavy precipitation in western and far-western region of Nepal washed away the harvesting crops indicate the burning example of Climate Change
• GLOF/Drifting snow/Snow avalanches – increased probability of GLOF and avalanche fall. Similarly, the drifting snow/snow avalanche that occurred on November 14, 2021 in western Nepal is another burning example of C-C.
• Early flowering of plants in Nepal (Laliguras is flowering in the month of February against the anticipated time of March).

Effect of Global Warming/Climate Change in Transportation Infrastructures

High Temperature and Heat Waves

High temperatures and heat waves are likely to become more intense and more frequent and last longer than they do today. These temperature increase will affect thermal expansion joints of bridge structures, increase stress and buckling of the steel members of steel truss bridges; Buckling of rail tracks; Cause more rapid degradation of road pavement; Runway pavement especially the asphalt pavements. In addition, construction workers will have to operate on reduced schedules or working at night as summer temperatures consistently might rise above 900 F in much of the country.

As more natural resources are consumed in production of building materials – more increase in heat stress and accelerated rate of GW. Similarly, increase in transportation facilities – more evolution of G-H gases and speedy rate of GW.

Atmospheric Co2 is a major cause of re-bar corrosion in bridge and other reinforced concrete structures. The increase in Co2 level associated with GW increases the carbonation process. As more temperature increase, the more cracks in the structural concrete. The impact of C-C on existing and new structure is considerable as corrosive damage disruptive to society and costly repair.

Heat Waves

• Heat waves cause Hurricane and other storms and are likely to become more common – damaging the engineering structures with the loss of life and properties
• Increase in intense tropical cyclone activity world-wide.

There are cases of bridge damage with storms and hurricanes. Record indicates – 8m storm surge during Hurricane Katrina laterally lifted the deck of the bay St. Louis Bridge off its pier. Beside this: Tacoma Narrow (Suspension Bridge) was broken into pieces and its superstructure fell down into the river by a strong wind in 1940. There are several cases in Nepal where, the shuttering and staging including the re-bar placing were completed for the concreting on next day and the same has been hit by strong wind & fell down into the riverbed.

Increased Intense Precipitation

Data indicates: Over the past 30-years, there has been a significant increase in the frequency and intensity of heavy precipitation events throughout the world and in Nepal as well. The small in total precipitation over this time period is the result of these more frequent heavier downpours. Sever storm create delays and disruptions to almost all types of transportation. Research work indicates:

• I in 100 years storm of precipitation may be 1 in 20 years event by 2090’s
• Inland waterways may experience higher and perhaps more frequent floods

Other possible impacts from change of precipitation pattern would include:

• Bigger and abrupt floods (higher water levels in lakes and river)
• Increased soil erosion and river incision
• Change in ground water table (creating foundation problem)

There are several examples from Nepal where bridge decks were lifted off their bearings by the combined effects of surcharge and entrapped flowing debris and deposited 100 of meter D/S.

Examples:

• Washout of 3-bridges (Malekhu, Belkhu and Mahadevbesi) along P-H in 1993
• Washout of Wakhley and Bhairabkunda bridges in 1995 and 1996 respectively
• Washout of Dware Bridge at Dipayal in1991.
• Some 20- number of bridges were seriously damaged/washout during 3-month from June –August 2021.
• Beside this, several buildings located along the riverside of Melamci River destroyed and one Bridge Rato was completely washed out by the devastating flood with debris and mud flow in the first week of June2021.

Climate and its Effects on Engineering Practices

As Engineers we are faced in designing structures and facilities in the context of climate future which is not equal to the climate past. The future climate as discussed is one of the more variability and change – more severe drought and summer and winter storms, more temperature rise, more precipitation and different long-term averages. This will impact the effectiveness of engineering structures and facilities which are influenced, directly or indirectly by weather. Recent research and reports toward adaptive projects are helping engineers to design structures and facilities which are robust to range of anticipated future and have the ability to adapt to new anticipated circumstances as emerge over time. We Civil Engineers are central to the planning, design, construction, operation, maintenance and decommissioning of infrastructure networks which underpin economic activity & protect human health and welfare. Major change to the design, construction and use will require to deliver large reduction in Greenhouse gas emission and to ensure sufficient resilience to cope with foreseeable climate change impacts.

The task is not easy: to workout answers to the challenges of the C-C, namely the Adaptation and Mitigation for old and new structures. Finding the optimal solution seems more complicated but is the responsibility of the Engineers.

Adaption:

Engineering Challenges and Opportunities

The scientific studies clearly indicate that threat from GW is real. Question arises: How should we respond or adapt the anticipated impact of GW especially as they impinge on engineering structure? The question facing the engineering profession whether adaption will be planned, studies response or haphazard reaction to events as they unfold. In many ways adaption is a classic risk management but it is complicated by inherent uncertainties associated C-C.

In mountain environment, where unpredictable natural forces are always in action, the engineers have to predict the mode of failure in different catastrophic situation and accordingly action is taken to design for it. Resultant damage must be accessible and reparable and restricted to the level such that the service can be restored in the shortest time.

Mitigation

Civil Engineers must lead the way in developing new technologies and materials to reduce the greenhouse emission over the whole life-cycle of the infrastructure systems. Most probably this kind of task is the responsibility of developed nations as they have: technical skills, physical resources, plant and equipment to facilitate any solution. By the contrast developing nations are characterized by dearth of resources, particularly financially and technologically.

We commit assisting government through the development of low-carbon infrastructure road map setting out key steps up to 2050. This will need to include:

Energy generation:

• An up scaling of renewal and low carbon generation including Nuclear, hydro, wind and solar
• Increase energy efficiency
• Development of new technologies including carbon capture and storage.

Transport:

• Encouraging non-structural solution such as new transportation system such as Electric buses and electric cars , improved intercity rail and tramways; project to reduce major checkpoints that cause transportation congestion etc.

Low Carbon Design:

• Lower embedded energy in construction and large reduction in whole life energy demand and emissions from infrastructure system.

Public Policy Priorities

Delivery of engineering solutions to reduce emission required to national government. At the international level the engineers should support the creation of binding international agreement for global emissions and equitable process for its achievement over long term. This will include:

• Establish clear and reasonable targets and timeframe for the reduction of Greenhouse gas emissions
• Stimulate private investment in Greenhouse gas reduction technologies
• Encourage action by other countries to reduce G-H emission

Case Study by the Author

In the recent years premature bridge failures were noticed by the collapse several bridges in the strategic road network of the country. Previously the collapses or severely damage rate was 2-3 numbers per year and now, in 21-years it has been increased by 5-6 per annum. Beside this, in the last monsoon 2021: some 20 number of bridge collapses were recorded during 2-months period.

To investigate the cause of premature failure, the author assembled some 45-events of such collapses or severely damaged bridges. They were subsequently analyzed. The result indicated that flood and foundation movements were responsible for almost 85% occurrences recorded. Main problem to cause such failures include: intense and prolonged rainfall, landslides, erosion, river flooding, river incision, disastrous GLOF, scours and siltation which are closely related to Global warming.

Conclusion

As Engineers we are faced with the designing structures and facilities in the context of climate future which is not equal to climate past. As discussed in different paragraphs with the consequences experienced – the future climate is one of more variability and change and more severe.

Recent focus on problem on GW is drawing world-wide attention to find out the effective way of reducing the emission of Greenhouses gases as large amount of natural resources (Fuels and fossils) consumed during construction of engineering infrastructure especially the transportation sector. This gives more justification of need for proper planning of the infrastructure to ensure that the resources are used optimally.

Recent research and reports toward adaptive project and policies are helping engineers to design structures and facilities which are robust to a range of anticipated future and have the ability to adapt to new unanticipated circumstances as emerge over time.

Terrain and forces of nature always dictate design & any design that does not address the ever-changing environment is doomed to failure. And lastly the Engineers should develop sound solutions for transportation system that will serve as until the end of the century.