Teesta River's 30-year erosion-accretion cycle reshapes 194 sq km of land, impacting agricultural use and settlement patterns.

Why It Matters

Understanding the dynamic interplay between riverine erosion and accretion is crucial for sustainable land management and infrastructure development in flood-prone regions. Designers and planners must account for these natural processes to create resilient solutions that mitigate risks and optimize resource utilization.

Key Finding

Over three decades, the Teesta River has caused substantial land erosion and deposition, altering land use by reducing agricultural areas and expanding settlements, with future trends suggesting further shifts away from agriculture.

Key Findings

• Approximately 194 sq km of land experienced erosion, with an equal area undergoing accretion between 1991 and 2021.
• Significant land-use changes occurred, with agricultural land being converted to other categories, and settlement areas showing a gradual increase.
• Future projections indicate a reduction in agricultural land and water bodies, with an increase in barren land and settlement areas.
• Reduced dry season flow and high monsoon discharge from upstream barrages contribute to severe erosion and siltation.

Research Evidence

Aim: To quantify and analyze the trends of river bank erosion and accretion along the Teesta River floodplain in Bangladesh over a 30-year period and assess their impact on land-use/land-cover changes.

Method: Remote Sensing and GIS Analysis

Procedure: The study utilized Landsat satellite imagery from 1991, 2001, 2011, and 2021 to map and quantify changes in river bank lines, erosion, and accretion. Land-use/land-cover (LULC) changes were analyzed in conjunction with these geomorphological shifts.

Context: Riverine floodplains, transboundary river systems, land-use planning, environmental management.

Design Principle

Design for dynamic environments by integrating natural geomorphological processes into planning and development.

How to Apply

For projects in riverine areas, conduct a thorough analysis of historical aerial or satellite imagery to understand erosion and accretion patterns. Incorporate findings into site selection, foundation design, and land-use zoning to build resilience.

Limitations

The study's findings are specific to the Teesta Floodplain and may not be directly generalizable to all river systems. Future projections are based on observed trends and can be influenced by unforeseen environmental or policy changes.

Student Guide (IB Design Technology)

Simple Explanation: This study shows how rivers like the Teesta can change the land over many years, causing some areas to disappear and others to form. This affects where people can farm and build houses.

Why This Matters: Understanding how the environment changes naturally helps you design things that are safer and last longer, especially in places affected by rivers or coastlines.

Critical Thinking: How might upstream water management decisions by one country directly impact land stability and resource availability in a downstream country, and what are the ethical considerations for designers in such transboundary contexts?

IA-Ready Paragraph: Research indicates that dynamic environmental processes, such as river bank erosion and accretion, can significantly alter land over time (Parvej et al., 2023). For instance, the Teesta River has reshaped approximately 194 sq km of land over three decades, impacting land use and settlement patterns. This highlights the critical need to incorporate such geomorphological changes into the analysis of potential design sites to ensure the resilience and longevity of any proposed development.

Project Tips

• When researching a site, look for historical maps or satellite images to understand how the land has changed over time.
• Consider how natural processes like erosion or flooding might impact your design over its lifespan.

How to Use in IA

• Use this research to justify the importance of considering environmental dynamics in your design process, particularly for site analysis and risk assessment.

Examiner Tips

• Demonstrate an understanding of how environmental factors, such as river dynamics, can influence design decisions and the long-term viability of a project.

Independent Variable: ["Time (years: 1991, 2001, 2011, 2021)","Upstream water discharge/management (implied)"]

Dependent Variable: ["River bank erosion (area, length)","River bank accretion (area)","Land-use/Land-cover (LULC) changes (e.g., agricultural land, settlement area, barren land, water bodies)"]

Controlled Variables: ["Geographical area (Teesta Floodplain, Bangladesh)","Satellite imagery resolution and type (Landsat)"]

Strengths

• Long-term temporal analysis (30 years) provides valuable trend data.
• Integration of geomorphological changes with land-use/land-cover analysis offers a holistic view of environmental impact.

Critical Questions

• To what extent can future land-use changes be accurately predicted based solely on past trends, and what other factors should be considered?
• What are the socio-economic implications of the projected reduction in agricultural land and water bodies for the local population?

Extended Essay Application

• Investigate the impact of historical landform changes on the design of resilient infrastructure in a specific coastal or riverine region.
• Explore how different land-use planning strategies can mitigate the risks associated with dynamic environmental processes like erosion and accretion.

Source

Three Decades of River Bank Erosion and Accretion Appraisal Along Bank Line Shifting Trend in A Transboundary River, Teesta Floodplain of BangladeshThree Decades of River Bank Erosion and Accretion Appraisal along Bank Line Shifting Trend in a Transbounda · Geoplanning Journal of Geomatics and Planning · 2023 · 10.14710/geoplanning.11.1.1-16