The Control of Nature by John McPhee

Why Geology Matters to Engineers

1. Introduction: Can Humans Control Nature?

The Control of Nature is a nonfiction book written by John McPhee and published in 1989. It explores humanity’s attempts to control powerful natural processes, including river migration, volcanic lava flows, and debris flows from mountainous terrain.

The book is based on three real-world case studies. Through these examples, McPhee examines the relationship between human engineering, geological processes, and natural hazards.

The central question is simple: Can engineering and technology completely control nature?

Humans can reduce natural hazards through dams, levees, drainage systems, debris basins, and other engineering structures. However, geological processes are complex, dynamic, and sometimes unpredictable.

The book demonstrates that successful engineering is not simply about building strong structures. It also requires understanding geological conditions, recognizing natural processes, assessing uncertainty, and adapting to changing conditions.

2. The First Story: Atchafalaya — Controlling a River

The first major case study examines the relationship between the Mississippi River and the Atchafalaya River in the United States.

Rivers naturally change their courses through erosion, sediment transport, and changes in channel geometry. The possibility of the Mississippi River shifting more of its flow toward the Atchafalaya River presented a major challenge because the Mississippi is important for navigation, trade, settlements, and economic activities.

To manage this risk, engineers constructed control structures, including the Old River Control Structure, to regulate the distribution of water between the two river systems.

However, river systems are continuously influenced by discharge, sediment transport, channel erosion, and changes in the surrounding landscape. Engineering structures can regulate river flow, but they cannot eliminate every natural process affecting a river.

Lesson for Engineering Geology: Before designing structures near rivers, engineers should understand River Morphology, Geomorphology, Sediment Transport, Erosion, and Flood History. A structure that controls present-day flow may still face challenges from future changes in the river system.

3. The Second Story: Cooling the Lava — Managing Volcanic Hazards

The second case study describes the 1973 Eldfell volcanic eruption on Heimaey Island, Iceland.

The eruption threatened settlements and an important harbour. The advancing lava flow created an urgent need to protect infrastructure and reduce the potential damage.

Scientists and emergency response teams attempted to cool the lava by pumping seawater onto it. Cooling helped solidify portions of the lava and influenced its movement, contributing to efforts to protect the harbour.

This event demonstrates how scientific knowledge and engineering intervention can help manage natural hazards. However, the effectiveness of such measures depends on lava temperature, flow rate, volume, direction, and local topography.

Lesson for Engineering Geology: In volcanic regions, development planning should consider Volcanic Hazard Assessment, Geological Mapping, Lava Flow Paths, and potential impact zones. Emergency engineering measures may reduce risk, but their effectiveness depends on geological conditions and available resources.

4. The Third Story: Los Angeles Against the Mountains — Managing Debris Flows

The third case study focuses on debris flows originating from the San Gabriel Mountains near Los Angeles, California.

A Debris Flow is a rapidly moving mixture of water, soil, rock fragments, and other materials. These flows can travel downslope and damage roads, buildings, drainage systems, and other infrastructure.

In some areas, wildfires remove vegetation and alter soil properties, increasing the potential for erosion and debris flows during subsequent intense rainfall.

To reduce the risk to communities, engineers have constructed Debris Basins to capture sediment and rock fragments before they reach developed areas.

Although these structures can significantly reduce damage, their capacity is limited. Basins may become filled with sediment, and exceptionally large events can overwhelm their design capacity. Regular inspection, sediment removal, and maintenance are therefore essential.

The case also reveals a fundamental problem: people develop settlements in hazardous mountainous areas and subsequently invest heavily in engineering structures to protect those settlements from natural processes.

Lesson for Engineering Geology: Understanding mountain hazards requires assessment of Slope Stability, Rockfall, Landslides, Debris Flows, Drainage Patterns, Weathering, Geological Structures, and Catchment Characteristics. Constructing a protective structure does not mean that the underlying hazard has disappeared.

5. Why Geology Matters to Engineers

One of the most important lessons from this book is that engineering design can become unsafe when natural processes are poorly understood.

A strong bridge may still be vulnerable if river erosion and Scour undermine its foundations. A dam may be at risk if Foundation Seepage, weak Rock Mass, or unfavourable Geological Structures have not been adequately investigated. A retaining wall may not provide sufficient protection if a large debris flow can originate higher up the slope.

Engineering design and geological investigation must therefore work together.

Geology helps engineers answer several important questions:

• What are the actual ground and Rock Mass conditions?
• Where does groundwater originate, and how does it flow?
• Which Geological Structures may influence stability?
• What natural processes could become active during the project’s lifetime?
• How might the proposed structure alter the surrounding natural system?
• What uncertainties remain after the available investigations?

The answers influence Site Selection, Design, Construction Methods, Monitoring, and Maintenance.

6. Applications to Hydropower Projects

Hydropower projects are closely connected to rivers, mountains, groundwater, and rock masses. The principles illustrated in this book are therefore highly relevant to dams, tunnels, surge tanks, penstocks, and powerhouses.

Dam Foundation: Foundation investigations should assess Rock Strength, Discontinuities, Weathering, Permeability, and Seepage conditions.

Spillway: In addition to Design Flood, engineers should evaluate Downstream Erosion, Energy Dissipation, and Scour.

Head Race Tunnel: Investigations should consider Rock Mass Quality, Fault Zones, Groundwater Inflow, Rock Burst, and potential Squeezing Ground, where relevant.

Slope Stability: Reservoir Rim slopes, tunnel portals, access roads, and other cut slopes should be assessed for the effects of Geological Structures, Groundwater, and Rainfall.

Monitoring: Geological conditions observed during construction should be compared with the assumptions made during investigation and design. Where necessary, the Geological Model, Design, and Support Measures should be updated.

In these situations, the role of an Engineering Geologist extends beyond geological mapping and rock description. Engineering Geologists help develop the Geological Model, identify potential hazards, interpret new ground conditions, and provide reliable information to support engineering decisions.

7. The Relationship Between Investigation, Design, and Monitoring

Geological conditions are complex, and initial investigations cannot reveal every detail of the ground.

Boreholes, Geological Mapping, Geophysical Surveys, Laboratory Testing, and Groundwater Investigations help engineers develop an understanding of subsurface conditions. However, the limitations and uncertainties of these investigations must also be recognized.

A successful project should follow a continuous process:

Investigation → Geological Model → Engineering Design → Construction Observation → Monitoring → Model Update

For example, a fault zone may be encountered during tunnel excavation even though it was not identified in the initial Geological Model.

The Engineering Geologist should assess its orientation, Rock Mass Condition, Groundwater Inflow, and potential impact on stability. The engineering team can then determine whether changes to the Support System, drainage arrangements, or excavation method are required.

This approach does not assume that nature can be completely controlled. Instead, it recognizes that engineering decisions must evolve as new geological information becomes available.

8. Should We Control Nature or Work With It?

The title The Control of Nature reflects the struggle between human ambition and natural processes. However, the deeper lesson is not that every natural process must be stopped.

Some processes can be controlled, others can be managed, and in certain situations the safest approach may be to avoid the hazard altogether.

For example, avoiding development in a high-risk area may be safer and more economical than constructing an extensive retaining system. Similarly, understanding river behaviour and applying appropriate Setbacks, Floodplain Management, and structural protection may be more effective than attempting to completely restrict a river’s natural movement.

Good engineering therefore involves more than constructing strong structures. It requires appropriate Site Selection, Geological Hazard Assessment, identification of potential Failure Modes, and long-term risk management.

9. Key Lessons from the Book

Lesson 1: Understanding nature is the foundation of good engineering.

Structural capacity alone is not enough. Engineers must also understand the natural processes that the structure will encounter throughout its design life.

Lesson 2: Geological Investigation is essential at every project stage.

It is not merely a preliminary activity. Geological information influences Site Selection, Design, Construction, Monitoring, and Maintenance.

Lesson 3: Every engineering structure has limitations.

Extreme floods, debris flows, lava flows, and long-term river changes may create conditions beyond those originally anticipated.

Lesson 4: Recognizing uncertainty is a professional responsibility.

Engineers should assess risks using available evidence, acknowledge limitations, monitor actual performance, and update designs when necessary.

Lesson 5: Large structures are not always the best solution.

Appropriate land-use planning, hazard avoidance, early warning systems, monitoring, and informed decision-making can sometimes reduce risk more effectively than structural intervention alone.

Conclusion: Understanding Nature Is the Foundation of Safe Engineering

The Control of Nature explores the Mississippi River system, volcanic lava flows in Iceland, and debris flows near Los Angeles to illustrate both the capabilities and limitations of engineering.

The book highlights the importance of scientific knowledge, practical engineering, and an understanding of the complexity of natural systems.

From an Engineering Geology perspective, its central message is clear: Do not treat nature merely as an obstacle to construction. Understand its geological history, present conditions, and potential future behaviour.

For hydropower and other infrastructure projects, this means integrating Geological Investigation, Engineering Design, Construction Observation, and Monitoring throughout the project lifecycle.

Successful engineering is not always about defeating nature. It is about understanding how natural systems work, reducing risk, making informed decisions, and adapting engineering solutions to changing ground conditions.

Final message: The best engineering does not assume that nature can always be controlled. It uses geological understanding, sound design, and continuous monitoring to build structures that are safer, more resilient, and better suited to the natural environment.