14.1 Land use changes and their geomorphic consequences
5 min read•july 30, 2024
Land use changes dramatically impact Earth's surface processes. , agriculture, and alter , rates, and watershed dynamics. These human activities can increase erosion, trigger , and modify river systems, leading to long-term landscape changes.
Mitigating these impacts requires careful planning and management. Regulatory approaches, best practices in agriculture and construction, and restoration efforts can help balance development with geomorphic sustainability. Understanding these processes is crucial for managing human-environment interactions and preserving landscape resilience.
Deforestation and Erosion
Impact on Soil Stability and Erosion Processes
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- Deforestation removes protective canopy and root systems stabilizing soil
- Increases soil exposure and vulnerability to erosion
- Reduces rainfall interception enhancing splash erosion
- Deforested areas experience higher rates of
- Increases potential for sheet, rill, and
- in deforested watersheds can increase by orders of magnitude (100-1000 times higher)
- Loss of organic matter input from trees alters
- Reduces soil cohesion and resistance to erosive forces
- Changes soil aggregate stability and porosity
Slope Stability and Long-term Effects
- Deforestation on steep slopes can trigger events
- Landslides and become more likely
- Reduced soil stability and increased contribute to slope failure
- Timescale of erosional response to deforestation varies
- Some effects occur immediately (increased surface runoff)
- Others manifest over decades or centuries (changes in soil structure)
- Long-term consequences of deforestation on erosion
- Altered (reduced water storage capacity)
- Impacts on downstream ecosystems (sedimentation in rivers and lakes)
- Potential for desertification in susceptible areas
Agriculture and Soil Properties
Tillage and Soil Structure
- Tillage practices disrupt soil structure
- Plowing and harrowing increase soil erodibility
- Can lead to formation of compaction layers (plow pans)
- Use of heavy machinery causes
- Reduces
- Increases surface runoff and erosion potential
- Impacts on soil physical properties
- Alters soil bulk density and porosity
- Changes soil water retention characteristics
Crop Management and Soil Health
- Crop rotation and cover cropping influence soil properties
- Affects soil organic matter content (typically increases with diverse rotations)
- Impacts nutrient cycling and soil aggregate stability
- Enhances (root systems of cover crops)
- practices impact soil health
- May deplete specific soil nutrients (nitrogen in corn monocultures)
- Reduces biodiversity, affecting long-term landscape resilience
- alter soil moisture regimes
- Can lead to (accumulation of salts in soil)
- Potential for soil crusting or enhanced erosion in poorly managed systems
Chemical Inputs and Landscape Modification
- Application of fertilizers and pesticides affects soil chemistry
- Impacts microbial activity and soil fauna
- Influences water quality through runoff and leaching
- and modify hillslope profiles
- Alters natural erosion and deposition patterns
- Can reduce overall soil loss on steep slopes
- Long-term effects of agricultural practices on landscape evolution
- Changes in soil depth and distribution across landscapes
- Alteration of natural drainage patterns and watershed characteristics
Land Use and Watersheds
Urbanization and Hydrological Changes
- Urbanization increases
- Reduces infiltration and
- Increases surface runoff and alters peak flow characteristics
- Changes in vegetation cover affect water balance
- Alters (typically decreases in urban areas)
- Impacts overall water yield from watersheds
- influences local climate
- Can alter precipitation patterns and intensity
- Potentially increases erosion during high-intensity storm events
River System Modifications
- and alter natural dynamics
- Modifies
- Changes channel migration patterns and floodplain development
- Construction of dams and reservoirs disrupts
- Alters (reduced peak flows, changed seasonality)
- Impacts sediment budgets and channel morphology downstream
- affects river-land interactions
- Influences bank stability and erosion rates
- Alters exchange of water and nutrients between terrestrial and aquatic systems
Cumulative Watershed Effects
- Land use changes lead to channel adjustments
- Can result in or aggradation
- Depends on balance between sediment supply and transport capacity
- across watersheds create complex responses
- Non-linear changes in channel morphology and floodplain development
- Potential for threshold behavior and regime shifts in river systems
- Long-term impacts on watershed hydrology and geomorphology
- Changes in and magnitude
- Alterations to sediment delivery to coastal areas and deltas
Land Use Planning for Mitigation
Regulatory Approaches
- Zoning regulations restrict development in sensitive areas
- Floodplains, steep slopes, coastal erosion zones protected
- Reduces risk of property damage and loss of life
- Building codes incorporate geomorphic considerations
- Foundation requirements in areas prone to soil movement
- Setback distances from active geomorphic features (cliffs, rivers)
- for large projects
- Evaluate potential geomorphic consequences before development
- Require mitigation measures to minimize impacts
Best Management Practices and Green Infrastructure
- Implementation of BMPs in agriculture and construction
- Erosion control measures (silt fences, mulching)
- Sediment basins to reduce sediment delivery to water bodies
- in urban planning mitigates hydrologic alterations
- Permeable pavements increase infiltration
- Bioswales and rain gardens promote natural water retention
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- Cluster development to preserve open spaces
- Green roofs reduce runoff from buildings
Restoration and Adaptive Management
- Restoration of degraded landscapes mitigates past impacts
- Reforestation programs to stabilize hillslopes
- Wetland reconstruction to improve water quality and flood control
- Watershed-scale planning approaches consider cumulative impacts
- Recognizes connectivity of geomorphic processes across landscapes
- Coordinates land use decisions across jurisdictional boundaries
- Incorporation of climate change scenarios in planning
- Anticipates potential geomorphic consequences of changing climate
- Develops adaptive strategies for long-term landscape resilience
- Balancing development with geomorphic sustainability
- Requires interdisciplinary collaboration (geomorphologists, engineers, planners)
- Implements strategies to respond to changing conditions
Key Terms to Review (43)
Adaptive Management: Adaptive management is a systematic approach to improving resource management by learning from the outcomes of past actions and adjusting strategies accordingly. This iterative process emphasizes flexibility and incorporates new information and changing conditions to inform decision-making. By continuously evaluating and refining management practices, adaptive management supports sustainable practices in various environmental contexts.
Bank stabilization: Bank stabilization refers to the processes and techniques used to prevent erosion and maintain the integrity of riverbanks or shorelines. This is crucial for protecting infrastructure, natural habitats, and water quality, especially in areas undergoing significant land use changes that can alter hydrology and sediment transport. Understanding bank stabilization helps connect the impacts of human activities on river systems and their geomorphic consequences.
Best management practices: Best management practices (BMPs) are a set of guidelines and techniques designed to mitigate negative environmental impacts associated with land use, especially during development and agricultural activities. BMPs aim to promote sustainable land management by minimizing erosion, improving water quality, and preserving natural habitats, all of which are crucial when considering the geomorphic consequences of land use changes.
Channel Aggradation: Channel aggradation is the process by which sediment builds up within a river or stream channel, raising the bed elevation and altering flow dynamics. This phenomenon often occurs when the rate of sediment supply exceeds the rate of sediment transport, leading to changes in the river's morphology and potential flooding issues. It can be influenced by various factors, including land use changes that impact sediment delivery and hydrology.
Channel incision: Channel incision refers to the process by which river channels cut down into the landscape, deepening their beds over time due to various geomorphic processes. This phenomenon is often influenced by factors such as land use changes, which can alter water flow and sediment transport, resulting in more aggressive erosion and deeper channels. The extent of channel incision can have significant effects on ecosystems, hydrology, and sediment dynamics in surrounding areas.
Contour farming: Contour farming is an agricultural practice where plowing and planting are done along the contours of the land rather than in straight lines. This method helps reduce soil erosion by creating natural barriers that slow water runoff, allowing more water to soak into the soil. By managing land in this way, it connects directly to soil classification, conservation efforts, and the geomorphic impacts of land use changes.
Cumulative effects: Cumulative effects refer to the combined impact of multiple activities or changes over time on the environment and landforms. These effects can accumulate from various land use changes, leading to significant geomorphic consequences that may not be evident when examining individual actions in isolation. Understanding cumulative effects is essential for assessing long-term sustainability and environmental health, especially as landscapes evolve due to human activity and natural processes.
Debris flows: Debris flows are fast-moving masses of loose soil, rock, and water that can travel down slopes due to gravity. They are a specific type of landslide characterized by their fluid-like behavior, allowing them to move rapidly and carry a wide variety of materials over considerable distances. The occurrence and intensity of debris flows are often influenced by factors such as rainfall, land use changes, and topography, making them significant in understanding geomorphic consequences.
Deforestation: Deforestation refers to the large-scale removal of trees and forests, primarily for agricultural expansion, urban development, or logging. This process significantly alters the landscape, affects biodiversity, and impacts various Earth system interactions, including climate regulation and soil stability.
Environmental Impact Assessments: Environmental Impact Assessments (EIAs) are systematic processes used to evaluate the potential environmental effects of proposed development projects before they are carried out. This assessment includes the analysis of possible changes to land use, the effects on ecosystems, and the implications for human communities. By identifying potential impacts early in the planning stage, EIAs aim to inform decision-makers and promote sustainable land use practices, minimizing negative geomorphic consequences.
Erosion: Erosion is the process by which soil, rock, and other surface materials are worn away and removed from their original location by natural forces such as water, wind, ice, or gravity. This process is essential in shaping landscapes and influencing sediment transport, which connects various components of the Earth's surface system.
Erosion resistance: Erosion resistance refers to the ability of a surface or material to withstand the forces that cause erosion, such as water, wind, and ice. This characteristic is crucial in understanding how landscapes evolve over time, especially when land use changes occur that may alter natural processes and expose surfaces to heightened erosion. Factors influencing erosion resistance include soil composition, vegetation cover, and land management practices, which all play a role in maintaining stability in various environments.
Evapotranspiration rates: Evapotranspiration rates refer to the combined process of evaporation from land surfaces and transpiration from plants, representing the movement of water from the soil and plants into the atmosphere. These rates are crucial in understanding water cycles, particularly how changes in land use—like urbanization or deforestation—can alter local climates, affect soil moisture, and impact water availability in a given area.
Flood frequency: Flood frequency refers to the statistical likelihood of a flood event occurring within a specific timeframe, typically expressed as a recurrence interval, such as a 100-year or 500-year flood. This concept helps in understanding how often floods are likely to happen in a particular area based on historical data, and it is crucial for assessing risks associated with flooding, especially in light of human activities and changes in land use.
Flow Regimes: Flow regimes refer to the characteristic patterns of flow in rivers and streams, influenced by factors such as water velocity, discharge, sediment transport, and channel morphology. These regimes can shift from laminar to turbulent flow depending on changes in water conditions, which are affected by both natural processes and human activities. Understanding flow regimes is crucial for assessing river health, sediment dynamics, and the impact of land use changes on aquatic ecosystems.
Green infrastructure: Green infrastructure refers to a strategically planned network of natural and semi-natural areas designed to manage stormwater, improve air quality, and enhance urban biodiversity. This approach integrates ecological functions into urban planning, allowing for the creation of green spaces that offer both environmental benefits and recreational opportunities. By using vegetation and permeable surfaces, green infrastructure supports sustainability and resilience in rapidly urbanizing areas.
Groundwater recharge: Groundwater recharge is the process through which water from precipitation or surface water infiltrates the ground and replenishes underground aquifers. This process is vital for maintaining the balance of groundwater levels and ensuring a sustainable supply of fresh water, particularly in areas where surface water may be scarce. Factors such as land use changes can significantly influence the rate and effectiveness of groundwater recharge.
Gully erosion: Gully erosion is the process where water runoff creates deep, narrow channels in the soil, significantly altering the landscape. This type of erosion often occurs when surface water flows rapidly down slopes, cutting into the ground and forming large ditches or gullies. It can lead to the loss of valuable topsoil and negatively impact agricultural productivity and water quality in nearby bodies of water.
Impervious Surface Area: Impervious surface area refers to land surfaces that do not allow water to infiltrate into the ground, such as concrete, asphalt, and buildings. This characteristic significantly alters natural water flow and drainage patterns, leading to increased runoff, reduced groundwater recharge, and various geomorphic consequences associated with land use changes.
Infiltration Rates: Infiltration rates refer to the speed at which water penetrates into the soil surface and moves into the ground. This process is influenced by factors such as soil texture, vegetation cover, land use practices, and moisture content, all of which can significantly change based on human activities. Understanding infiltration rates is crucial for managing water resources, predicting runoff, and assessing the impact of land use changes on the environment.
Irrigation methods: Irrigation methods refer to the various techniques employed to supply water to crops and agricultural lands, ensuring their growth and productivity. These methods can significantly influence land use, agricultural practices, and water management strategies, leading to substantial geomorphic consequences as landscapes are altered to accommodate these systems. The effectiveness and environmental impacts of these methods can shape both the physical landscape and the socio-economic conditions of the areas where they are implemented.
Landslides: Landslides are the downward movement of rock, soil, and other materials on a slope due to gravity. This process can be influenced by various factors such as the stability of slopes, land use practices, and changing climate conditions. Understanding landslides is crucial as they can cause significant damage to infrastructure, alter landscapes, and impact ecosystems.
Low impact development techniques: Low impact development techniques are sustainable design approaches aimed at managing stormwater runoff in urban environments while minimizing environmental impact. These techniques focus on preserving natural hydrology and reducing the burden on traditional drainage systems by incorporating features such as green roofs, permeable pavements, and rain gardens. This approach not only helps mitigate flooding and water pollution but also enhances the ecological health of urban areas.
Mass wasting: Mass wasting refers to the downward movement of soil, rock, and debris under the influence of gravity. This process plays a crucial role in shaping the landscape by transporting materials from higher elevations to lower areas, which affects landforms, ecosystems, and human activities. It is influenced by various environmental factors and is closely related to soil erosion, slope stability, and the impacts of land use changes on geomorphic processes.
Monoculture farming: Monoculture farming is an agricultural practice that involves the cultivation of a single crop species over a large area for consecutive seasons. This method maximizes efficiency and yield for specific crops, but it can lead to several environmental issues such as soil degradation and increased vulnerability to pests and diseases. Monoculture farming significantly impacts land use and can trigger geomorphic changes due to altered soil structure, erosion patterns, and hydrological responses.
Pore water pressure: Pore water pressure is the pressure exerted by water within the pores of soil or rock, which plays a crucial role in influencing the mechanical behavior of geological materials. It acts against the weight of overlying materials, impacting the effective stress within the soil. Understanding pore water pressure is essential for evaluating slope stability and recognizing how land use changes can alter geomorphic processes, such as erosion and sediment transport.
Restoration Ecology: Restoration ecology is the scientific study and practice of renewing and restoring degraded, damaged, or destroyed ecosystems and habitats to their natural state. It focuses on understanding ecological processes and the interplay between organisms and their environment, aiming to bring back biodiversity, ecosystem functionality, and resilience. This field is crucial for addressing issues related to land use changes and for managing coastal ecosystems, including barrier islands and lagoons, where human activities can significantly alter natural landscapes.
Rill Erosion: Rill erosion is a form of soil erosion that occurs when water runoff forms small channels or grooves on the surface of the soil. These channels, typically just a few inches deep, can expand over time if not controlled, leading to significant soil loss. Rill erosion is particularly common in areas with steep slopes or insufficient vegetation, as the lack of plant cover allows water to flow more freely and dislodge soil particles.
Riparian zone modification: Riparian zone modification refers to the alteration of the areas adjacent to rivers and streams, which are crucial for maintaining ecological balance and water quality. These modifications often occur due to human activities such as urban development, agriculture, and deforestation, leading to changes in vegetation, soil composition, and hydrology. The impact of these modifications can result in increased erosion, reduced biodiversity, and changes in sediment transport dynamics.
River continuity: River continuity refers to the unbroken flow and connectivity of a river system, which is essential for maintaining the ecological health and hydrological function of the river. This concept is tied to how changes in land use, such as urban development or agriculture, can disrupt natural water flow, sediment transport, and habitat availability for aquatic life. When continuity is compromised, it can lead to geomorphic changes that affect both the river and the surrounding landscape.
Salinization: Salinization is the process by which water-soluble salts accumulate in the soil, often due to irrigation practices and evaporation. This buildup can lead to adverse effects on soil health, agricultural productivity, and ecosystem balance, especially in arid and semi-arid regions where water evaporation rates are high and rainfall is limited.
Sediment transport processes: Sediment transport processes refer to the mechanisms by which sediment is moved from one location to another through natural forces such as water, wind, and ice. These processes play a crucial role in shaping landscapes, influencing landforms, and altering ecosystems. Understanding how these processes are affected by human activities like land use changes and urbanization is vital, as they can lead to significant geomorphic consequences and impact surface processes.
Sediment yield: Sediment yield refers to the amount of sediment that is transported from a specific area to a river system over a given period of time, typically measured in tons per square kilometer per year. It is influenced by factors such as erosion, land use practices, and hydrology, playing a crucial role in shaping river morphology and sediment transport dynamics. Understanding sediment yield is essential for managing river systems, particularly in the context of human activities and land use changes that can alter natural processes.
Sheet erosion: Sheet erosion is the removal of a thin layer of soil from a large area of land, typically caused by rainfall and surface runoff. This process can significantly impact soil quality and agricultural productivity, as it often leads to the loss of nutrient-rich topsoil. Understanding sheet erosion helps in recognizing its role in soil conservation efforts and the broader implications of land use changes.
Soil compaction: Soil compaction is the process by which soil particles are pressed together, reducing the amount of air and water in the soil. This results in increased density and strength but can lead to reduced pore space, which affects water infiltration and root growth. In the context of land use changes, soil compaction is a significant geomorphic consequence as it alters the physical properties of the soil, influencing water movement, plant growth, and overall land productivity.
Soil Stability: Soil stability refers to the ability of soil to maintain its structure and resist erosion, compaction, and other forms of disturbance. This concept is crucial when considering land use changes, as alterations such as urban development or agriculture can significantly impact soil integrity, leading to increased susceptibility to erosion and degradation.
Soil structure: Soil structure refers to the arrangement of soil particles and the spaces between them, creating various formations such as aggregates, clods, and granules. This arrangement affects how air, water, and nutrients move through the soil, influencing plant growth and the overall health of the ecosystem. Understanding soil structure is crucial for assessing how land use changes can impact geomorphic processes like erosion, sedimentation, and water retention.
Stream channelization: Stream channelization is the process of modifying the physical characteristics of a stream or river channel to improve flow efficiency, often through the construction of straightened, widened, or deepened channels. This practice aims to control flooding, improve navigation, and facilitate land use changes, but it can lead to significant geomorphic consequences such as altered sediment transport and habitat degradation.
Surface Runoff: Surface runoff refers to the flow of water that occurs when excess rainwater, meltwater, or irrigation water flows over the ground surface. This phenomenon is crucial in understanding how land use changes, such as urbanization or deforestation, can impact geomorphic processes. It affects soil erosion, water quality, and the hydrology of an area, influencing both natural landscapes and human infrastructures.
Terracing: Terracing is a land management technique that involves creating stepped levels on sloped terrain to reduce soil erosion and manage water runoff. This method helps to slow down water flow, which decreases the potential for soil loss while allowing for more effective agricultural practices. By transforming steep slopes into flat areas, terracing not only conserves soil and water but also enhances land usability and productivity.
Urban heat island effect: The urban heat island effect refers to the phenomenon where urban areas experience significantly warmer temperatures than their rural surroundings due to human activities and alterations in land use. This effect arises from factors like the concentration of buildings, roads, and other infrastructure that absorb and retain heat, as well as reduced vegetation and soil that would otherwise provide cooling through evapotranspiration. Consequently, this leads to increased energy consumption, elevated emissions of air pollutants, and enhanced heat-related health risks.
Urbanization: Urbanization is the process by which rural areas become increasingly transformed into urban areas, leading to population growth and expansion of city spaces. This shift impacts various aspects of the environment, social structures, and economic activities, often altering natural landscapes and influencing surface processes in significant ways.
Watershed hydrology: Watershed hydrology is the study of how water moves through a watershed, including precipitation, evaporation, infiltration, and runoff processes. Understanding this term is crucial for assessing how land use changes impact water flow, quality, and availability within a watershed, ultimately influencing geomorphic processes such as erosion and sediment transport.