Guidelines for selection and development of the site for building in hill areas, Part 1: Microzonation of urban centres

IS 14243 (Part 1) - Scope & Key Specifications

1. Seismic Hazard Classification (Clause 4.2 & Table 1)

• Based on Peak Ground Acceleration (PGA) at urban center:

• Design earthquake and stability analysis must be based on this classification.

2. Ground & Soil Considerations (Clause 4.7)

• Check long-term settlements in reclaimed/solid waste disposal areas.
• Settlement effects due to soil consolidation and organic material must be evaluated under in-situ seasonal conditions.

3. Geomorphology (Clause 3.4.1.1.2)

• Terrain evaluation based on:
  • Slope categories:
    • Very gentle: 0°–15°
    • Gentle: 15°–25°
    • Moderately steep: 25°–35°
    • Steep: 35°–45°
    • Very steep: >45°
  • Relative relief: scarp faces, valley shape, depression zones, inundation areas.

Summary Diagram: Seismic Hazard Classification Flow

flowchart TD
    A[PGA Measurement] --> B{PGA Value}
    B -->|<0.10g| C[Class I - Low]
    B -->|0.10g to 0.25g| D{Active Fault?}
    D -->|No| E[Class II - Moderate]
    D -->|Yes| F[Class III - High]
    B -->|>0.25g| G{Active Fault within 10 km?}
    G -->|No| H[Class III - High]
    G -->|Yes| I[Class IV - Extreme]

Note: Use seismic hazard class to determine design

Primary Factors for Microzonation Maps (IS 14243 Part 1)

Key Parameters (Clauses 2.2, 3.1)

• Scale of base maps depends on:
  • Size of urban center
  • Relief/topography
  • Surficial soil and rock strata
  • Drainage pattern and density
• Recommended topographic map scales:
  • 1:10,000 scale with 2 m contour intervals for mountainous/high relief areas
  • 1:25,000 scale with 3-5 m contour intervals for moderate relief
• Base maps must be prepared if unavailable.

Primary Factors Governing Microzonation (Clause 3.1)

• Regional and local geology
• Hydrological conditions (water table, drainage)
• Human activities (mining, construction)
• Urban size and building types

Seismic Hazard Classification (Clause 4.2, Table 1)

Stability Assessment (Clause 4.3)

• Demarcate homogeneous lithology zones (hard rock, soft rock, terraces, fans, flood plains, slide debris).
• Slope stability criteria:
  • Rocky terrain: slopes < 25° generally stable
  • Surficial deposits: dry slopes < 20° generally stable
• Identify high water table zones prone to liquefaction or settlement.

Summary Diagram: Microzonation Factors

graph TD
  A[Microzonation Maps] --> B[Base Map Scale]
  A --> C[Geology & Lithology]
  A --> D[Hydrology & Water Table]
  A --> E[Seismic Hazard Class]
  A --> F[Topography & Slope]
  A --> G[Human Activities]

  B --> B1[1:10,000 (High Relief)]
 

IS 14243 Part 1: Key Points on Regional and Local Geology

1. Regional Geology (Clause 3.2)

• Study area around urban center for hazard intensity (earthquakes, floods).
• Include:
  • Physiography: landforms, drainage.
  • Geological history.
  • Geological formations & surficial deposits.
  • Structural features: folds, faults, fractures, joints.
  • Active faults/shear zones.
  • Hydrological conditions: groundwater table configuration.

2. Local Geology (Clause 3.3)

• Data collection via literature, site inspection, field exploration.
• Include:
  • Geomorphology: slope, relief, landforms, drainage, springs, land use.
  • Soil/rock type, thickness, stability.
  • Hydrology: water table, seepage, permeability.
  • Local structural features.
  • Past disaster effects.
  • Geotechnical properties of materials.

3. Slope Stability & Terrain Classification (Clause 4.3 & 3.4.1.1.2)

• Rocky terrain slopes < 25° generally stable.
• Surficial deposits slopes < 20° generally stable.
• Areas with high water table or saturation need liquefaction/settlement evaluation.

4. Geomorphology Parameters (Clause 3.4.1.1.2)

• Slope character & relative relief for terrain evaluation.
• Relief indicates scarps, valleys, depressions, inundation zones.

flowchart TD
    A[Regional Geology Study] --> B[Physiography & Drainage]
    A --> C[Geological History & Formations]
    A --> D[Structural Features & Faults]
    A --> E[Hydrological Conditions

IS 14243 Part 1: Procedures for Microzonation - Key Points

1. Map Scale Selection (Clause 2.2)

• Based on:
  • Urban center size
  • Relief of area
  • Nature of surficial soil/rock strata
  • Drainage pattern & density
• Scale & contour intervals:
  • High relief/mountainous: 1:10,000 scale, 2m contour interval
  • Moderate relief: up to 1:25,000 scale, 3-5m contour interval
• Prepare topographic base maps if unavailable.

2. Primary Factors for Microzonation (Clause 3.1)

• Regional geology
• Hydrological conditions
• Local geology
• Human activity hazards (mining, construction)
• Consider size and purpose of urban sectors.

3. Objectives of Microzonation

• Identify unstable zones prone to:
  • Ground failures
  • Inundation/water-logging
  • Earthquake amplification
• Demarcate:
  • High-risk areas
  • Negligible risk zones
• Aid in land-use planning, building siting, and hazard mitigation.

4. Map Content & Reporting (Clause 4.7)

• Show areas likely inundated during 100-year floods.
• Indicate ground failure types and extents.
• Include reclaimed/solid waste areas with long-term settlement checks.
• Provide explanatory report on methodology and evaluation.

Summary Table: Map Scale & Contour Interval

Conceptual Flow of Microzonation Procedure

flowchart TD
    A[Start: Define Urban Area] --> B[Collect Geological & Hydrological Data]
    B --> C[Prepare Topographic Base Maps]
    C --> D[Analyze Soil, Rock & Drainage Patterns]
    D --> E[Identify Hazard Zones (Ground Failures, Floods)]
    E --> F[Demarcate Risk Zones on Microzonation Map]
    F --> G[Prepare Report with Methodology & Recommendations]
    G

Key Specifications for Preparation of Topographic Maps (IS 14243 Part 1):

1. Scale & Contour Interval (Clause 2.2)

• Mountainous/high relief areas:
  • Scale: 1:10,000
  • Contour interval: 2 m
• Moderate relief areas:
  • Scale: up to 1:25,000
  • Contour interval: 3 to 5 m
• Maps must be prepared if unavailable, as they form the base for further mapping.

2. Slope Classification (Clauses 3.4.1.1.2 & 4.1)

• Prepare slope maps delineating these categories.

3. Map Types to Prepare (Clause 4.1)

• Topographic map (base map)
• Slope map (using above slope categories)
• Geology map (rock outcrops, surficial deposits)
• Land use/land cover map
• Hydrological map showing:
  • Perennial/seasonal streams
  • Irrigation canals, open drains
  • Runoff levels (normal, monsoon, 100-year flood)
  • Groundwater table contours

4. Stability Guidelines (Clause 4.3)

• Rocky terrain: slopes < 25° generally stable.
• Surficial deposits: dry slopes < 20° generally stable.
• Areas with high water table or saturated soils require detailed study for liquefaction and settlement risks.

flowchart TD
    A[Prepare Topographic Map] --> B[Slope Map]
    A --> C[Geology Map]
    A --> D[Land Use & Cover Map]
    A --> E[Hydrological Map]
    B --> F{Slope Categories}
    F --> G[Very gentle <15°]
    F --> H[Gentle 15°-

Seismic Hazard Classification (IS 14243 Part 1, Clause 4.2 & Table 1)

Seismic hazard class is determined based on Peak Ground Acceleration (PGA) at the urban center:

Key Specifications:

• Active faults within 10 km increase hazard class to IV.
• Geological, slope, and hydrological maps must be used to identify stable zones.
• Slopes < 25° (rocky terrain) and < 20° (surficial deposits) are generally stable.
• Areas with high water table or saturated soils require detailed liquefaction and settlement studies.

Summary Diagram:

flowchart TD
    A[PGA Measurement] --> B{PGA Range}
    B -->|<0.10g| C[Class I: Low]
    B -->|0.10g to <0.25g| D{Active Faults?}
    D -->|No| E[Class II: Moderate]
    D -->|Yes| F[Class IV: Extreme]
    B -->|≥0.25g| G{Active Faults?}
    G -->|No| H[Class III: High]
    G -->|Yes| F

Use this classification for design earthquake parameters and stability analysis of soil/rock as per IS 14243 Part 1.

Geological and Slope Stability Assessment per IS 14243 Part 1:

Key Specifications:

• Slope Stability by Terrain Type (Clause 4.3):

  • Rocky terrain: slopes < 25° generally stable.
  • Surficial deposits (dry slopes): slopes < 20° generally stable.
  • Slopes exceeding these require detailed factor of safety (FoS) analysis.

• Material Classification (Clause 3.4.1.1.1):

  1. Natural materials (rocks, terraces, alluvial fans, etc.)
  2. Disturbed materials (due to ground failures)
  3. Reclaimed land and waste dumps

• Hydrological Conditions (Clause 3.4.1.1.3):

  • Evaluate surface runoff, water spread, marshy areas, groundwater table, springs.
  • Consider pore water pressure effect on shear strength.
  • Account for normal, seasonal, and 100-year flood levels.

Stability Evaluation:

• Factor of Safety (FoS) against sliding:

[ FoS = \frac{C' + (\sigma - u) \tan \phi'}{\tau} ]

Where:

• ( C' ) = effective cohesion

• ( \sigma ) = normal stress

• ( u ) = pore water pressure

• ( \phi' ) = effective angle of internal friction

• ( \tau ) = shear stress on failure plane

• Slope Stability Zones:

Recommendations:

• Mark zones of homogeneous lithology.
• Superimpose slope and hydrological maps for stability mapping.
• Identify high water table zones for liquefaction and settlement risk.
• Plan open cut slopes considering local stability (Clause 3.4.1.3.1).

flowchart TD
    A[Geological Map] --> B[Demarcate Lithology Zones]
    C[Slope Map] --> D[Identify Stable Slopes (<25

Key Specifications & Evaluation Criteria for Rocky Terrain Stability (IS 14243 Part 1):

1. Slope Stability Classification (Clause 4.3 & 3.4.1.1.2)

• Rocky terrain slopes < 25° → Generally stable.
• Surficial deposits slopes < 20° (dry) → Generally stable.
• Slopes beyond these limits require detailed stability analysis (Factor of Safety).

2. Material Classification (Clause 3.4.1.1.1)

• Natural materials: rocks, terraces, alluvial fans, flood plains.
• Disturbed materials: due to ground failures.
• Reclaimed land and solid waste dumps.
• Strength parameters and structural weaknesses must be assessed.

3. Failure Mode Identification (Clause 4.4)

• Identify zones prone to:
  • Rock falls
  • Rock slides
  • Creeps
  • Debris flows

4. Factor of Safety (FoS) Evaluation

• For slopes > stable limits, calculate FoS considering:
  • Shear strength parameters (cohesion c, friction angle φ)
  • Slope geometry and groundwater conditions
  • Use standard slope stability methods (e.g., Limit Equilibrium Method)

Simplified FoS Formula (for planar slip):

[ FoS = \frac{c' \cdot L + (W \cos \alpha - uL) \tan \phi'}{W \sin \alpha} ]

Where:

• ( c' ) = effective cohesion
• ( \phi' ) = effective friction angle
• ( W ) = weight of sliding mass
• ( \alpha ) = slope angle
• ( u ) = pore water pressure
• ( L

Assessment of Glacial Materials as per IS 14243 Part 1

Key Points & Specifications:

• Degree of Saturation (Clause 4.5):
  Evaluate saturation to assess loss of strength and potential debris flow in glacial materials.
  [ S_r = \frac{V_w}{V_v} \times 100% ]
  where (S_r) = degree of saturation, (V_w) = volume of water, (V_v) = volume of voids.

• Material Classification (Clause 3.4.1.1.1):

  • Natural materials (including glacial deposits)
  • Disturbed materials (due to ground failures)
  • Reclaimed land and solid waste dumps

• Stability Parameters (Clause 4.3):

  • Slope stability depends on lithology and slope angle.
  • Rocky terrain: slopes < 25° generally stable.
  • Surficial deposits (including glacial till): dry slopes < 20° generally stable.
  • Areas with high water table or saturation require detailed factor of safety (FoS) analysis.

• Avalanche & Landslide Debris (Clause 3.4.1.2.5):
  Study debris characteristics for hazard evaluation.

Recommended Stability Check Formula (FoS):

[ FoS = \frac{c' + (\sigma - u) \tan \phi'}{\tau} ]

• (c') = effective cohesion
• (\sigma) = normal stress
• (u) = pore water pressure
• (\phi') = effective angle of internal friction
• (\tau) = shear stress

Summary Table: Stability of Slopes in Glacial Materials

flowchart TD
    A[Glacial Material] --> B{Degree of Saturation}
    B -->|Low Saturation| C[Stable

Study of Terrace and Fan Deposits as per IS 14243 Part 1

Key Specifications:

• Classification (3.4.1.1.1):

  • Natural materials include terraces, fans, flood plains, alluvial deposits, etc.
  • Strength parameters and structural weaknesses must be analyzed for stability.

• Stability Assessment (4.3 & 4.6):

  • Identify homogeneous lithology zones (terraces, fans, etc.) using geological, slope, and hydrological maps.
  • Stable slopes:
    • Rocky terrain: slope < 25°
    • Surficial deposits (terraces/fans): dry slopes < 20°
  • Areas with high water table or saturation require liquefaction and settlement analysis under earthquake loading.

Stability Evaluation:

• Calculate Factor of Safety (FOS) for slopes > stable limits using shear strength parameters:
  [ FOS = \frac{c' + (\sigma - u) \tan \phi'}{\tau} ] where:
  • (c') = effective cohesion
  • (\phi') = effective angle of internal friction
  • (\sigma) = normal stress
  • (u) = pore water pressure
  • (\tau) = shear stress on failure plane

Other Considerations:

• Identify previous ground failures and debris zones (3.4.1.2.5) for hazard evaluation.
• Study earthquake effects on stability and potential liquefaction.

flowchart TD
    A[Geological Map] --> B[Identify Lithology Zones]
    B --> C[Slope Map & Hydrological Map]
    C --> D{Slope Stability Check}
    D -->|Slope < 20° (Surficial)| E[Generally Stable]
    D -->|Slope < 25° (Rocky)| E
    D -->|Slope > Limits| F[Detailed FOS Analysis]
    F --> G[Consider Strength Parameters & Water Table]
    G --> H[Estimate Stability under Earthquake]

This approach ensures a comprehensive stability assessment of terrace and fan deposits per IS 14243 Part 1.

Considerations for Reclaimed and Waste Disposal Areas (IS 14243 Part 1)

Key Points from Clauses:

• Clause 3.4.1.3.5:

  • Unstable foundations on slopes with reclaimed land or waste dumps cause unequal settlements and failures.
  • Dumps often contain organic materials that decay, creating voids and differential settlements.
  • Presence of contaminants and empty spaces reduces soil strength and stability.

• Clause 4.7:

  • Long-term settlements due to soil consolidation and organic decomposition must be evaluated under in-situ conditions across seasons.
  • Use microzonation maps to identify flood-prone and ground failure-prone areas for safe construction zones.

Design & Evaluation Guidelines:

• Settlement Estimation:
  Consider primary consolidation and secondary compression for organic fills:
  [ S = S_c + S_s ]
  where

  • ( S_c ) = primary consolidation settlement
  • ( S_s ) = secondary (creep) settlement due to organic decay

• Consolidation Settlement (Terzaghi’s Theory):
  [ S_c = \frac{H}{1+e_0} \log \frac{\sigma'_0 + \Delta \sigma'}{\sigma'_0} ]
  where

  • ( H ) = thickness of compressible layer
  • ( e_0 ) = initial void ratio
  • ( \sigma'_0 ) = initial effective stress
  • ( \Delta \sigma' ) = increase in effective stress

• Recommendations:

  • Conduct seasonal field monitoring for settlements.
  • Use geotechnical investigations to characterize waste material properties.
  • Avoid heavy structures on highly organic or loosely filled dumps.
  • Employ ground improvement or deep foundations if necessary.

Summary Table: Key Considerations

IS 14243 Part 1 — Causative Factors of Land Hazards

Key Points from Clauses 3.4, 4.3, and 3.4.1.1.1:

1. Categories of Land Hazards:

• Ground Failures: Landslides, slope failures, liquefaction, settlement.
• Floods and Inundations: Waterlogging, flooding hazards.

2. Stability Criteria Based on Terrain and Slope (Clause 4.3):

• Areas with slopes beyond these limits require detailed factor of safety (FoS) analysis.
• High water table and saturated soils need liquefaction and settlement assessment.

3. Material Classification (Clause 3.4.1.1.1):

• Natural materials: Rocks, terraces, alluvial fans, flood plains, glacial deposits.
• Disturbed materials: Due to ground failures.
• Reclaimed land: Solid waste dumps, reclaimed soils.

4. Factor of Safety (FoS) for Slope Stability (General Formula):

[ FoS = \frac{\text{Shear Strength of Soil (c + \sigma \tan \phi)}}{\text{Shear Stress due to slope}} ]

Where:

• ( c ) = cohesion,
• ( \phi ) = angle of internal friction,
• ( \sigma ) = normal stress.

FoS > 1.5 generally indicates stable slopes.

Summary Diagram of Hazard Identification Process

flowchart TD
    A[Geological Map] --> B[Identify Homogeneous Lithology]
    B --> C[Superimpose Slope Map]
    C --> D{Slope Criteria}
    D -->|Rocky < 25°| E[Stable Area]
    D -->|Surficial < 20°| E
    D -->|Others| F[Detailed FoS Study]
    E --> G[Mark Stable Zones]
    F --> G
    G --> H[Hydrological Map Overlay]
    H --> I[Identify High Water Table Zones]
    I --> J[Assess

Instabilities Due to Human Activities (IS 14243 Part 1, Clause 3.4.1.3):

• Causes:
  • Mining and excavations without proper planning.
  • Unplanned urban development.
  • Construction interfering with existing drainage systems.
  • Building on flood plains or near shorelines.
  • Construction on weak/unstable foundations.

Key Specifications & Considerations:

• Planning & Execution: Proper site investigation and planning to avoid interference with natural drainage and unstable zones.
• Foundation Assessment: Use geotechnical investigations to identify weak soils.
• Drainage: Maintain or improve natural drainage to prevent waterlogging and erosion.
• Urban Development: Follow zoning and land-use regulations to avoid construction on vulnerable lands.

Important Formulas & Checks (General Guidance):

• Factor of Safety (FoS) against slope failure:

[ FoS = \frac{\text{Shear Strength of Soil}}{\text{Shear Stress due to Loads}} ]

• Allowable bearing capacity check:

[ q_{allow} = \frac{q_{ult}}{FS} ]

Where:

• (q_{ult}) = ultimate bearing capacity (from soil tests)
• (FS) = factor of safety (usually 2.5 to 3 for human activity zones)

Summary Table (Conceptual):

flowchart TD
    A[Human Activities] --> B[Mining/Excavation]
    A --> C[Unplanned Urban Development]
    A --> D[Drainage Interference]
    A --> E[Construction on Weak Foundations]
    B --> F[Ground Collapse]
    C --> G[Soil Erosion & Instability]
    D --> H[Waterlogging & Erosion]
    E --> I[Foundation Failure]

Note: IS 14243 Part 1 emphasizes prevention through planning and geotechnical assessment rather than prescribing fixed formulas for human activity-induced instabilities.

IS 14243 Part 1: Floods and Inundations — Key Points & Specifications

Classification of Floods (Clause 3.4.2)

• Inland floods: Floods on rivers.
• Deltaic floods: Flooding in delta areas.
• Sea waves: Due to cyclones.
• Excessive precipitation: From cyclones/cloud bursts.

Design Considerations

• Establish maximum flood level from historical data.
• Construction must be above max flood level to avoid inundation.
• Near shorelines/flood plains, consider:
  • High tide levels
  • Sea waves
  • Backflow through drains

Extreme Conditions (Clause 3.4.1.2.2 & 3.4.1.2.4)

• Consider effects of:
  • Cloud bursts, cyclones, tsunamis.
  • Collapse of upstream water-retaining structures.
  • Sudden debris flow from bursting debris dams (e.g., landslides, glacial debris).

Recommended Formula for Flood Level Estimation

[ H_{max} = H_{historic} + S + C ]

Where:

• (H_{max}) = Design flood level
• (H_{historic}) = Highest recorded flood level
• (S) = Freeboard (safety margin, typically 0.5 to 1.0 m)
• (C) = Climate change allowance (if applicable)

Summary Table: Flood Hazard Parameters

flowchart TD
    A[Flood Hazard Types] --> B[Inland Floods]
    A --> C[Deltaic Floods]
    A --> D[Sea Waves (Cyclones)]
    A --> E[Excessive Precipitation]
    F[Design Considerations] --> G[Max Flood Level]
    F --> H[Freeboard]
    F --> I[Backflow & Drainage]
   

IS 14243 Part 1 (1995) — Guidelines for Site Selection & Development in Hill Areas

Key Specifications for Microzonation & Site Development

• Microzonation Maps:

  • Delineate areas prone to:
    • Ground failures (landslides, rock falls, avalanches)
    • Flood inundation (100-year flood zones)
    • Water-logging and soil consolidation settlements
  • Identify stable, unstable, and potentially hazardous zones.
  • Used for planning building complexes, green belts, and open spaces.

• Assessment Parameters:

  • Local geomorphology, geology, hydrology.
  • Natural hazards: earthquakes, floods, cyclones.
  • Procreated hazards: mining, unplanned excavation.
  • Long-term soil settlement checks in reclaimed/solid waste areas.

• Development Guidelines:

  • Avoid construction in high-risk zones.
  • Design green belts and open spaces as buffers.
  • Use microzonation data for master planning & land use.

Important Considerations

Summary Flowchart of Site Selection Process

flowchart TD
    A[Start: Urban Centre Planning] --> B[Collect Geological & Hydrological Data]
    B --> C[Prepare Microzonation Maps]
    C --> D{Identify Zones}
    D -->|Stable| E[Suitable for Construction]
    D -->|Unstable| F[Restrict Construction; Plan Green Belts]
    D -->|Flood Prone| G[Plan Flood Mitigation & Open Spaces]
    E & F & G --> H[Finalize Master Plan & Land Use]
    H --> I[Site Development & Monitoring]

Note: For detailed procedures, refer to Clause 4.7 and related sections of IS 14243-1 (1995). Always round off values per IS 2:1960 rules.