Guidelines on Landscaping and Tree Plantation

IRC SP 21 — Scope Overview

The Scope section (Page 2) defines the extent of landscaping and roadside plantation guidelines for highways, focusing on:

• Roadside plantation for safety, aesthetics, and environmental benefits.
• Application to rural and urban highways.
• Guidelines for highway structures, appurtenants, and slope protection.
• Emphasis on maintenance and improvement of existing roadside landscapes.

Key Specifications & Tables from Scope:

Typical Cross-Section Highlights:

graph LR
A[Earthen Shoulder] --> B[Plant Row 1 (333 trees/km)]
B --> C[Carriageway]
C --> D[Plant Row 2]
D --> E[Plant Row 3]
E --> F[Earthen Shoulder]

Notes:

• All dimensions in mm.
• Refer to Appendix II for slope protection and detailed landscaping.
• Plant species and spacing depend on local conditions (see Appendix I).
• Planting improves road safety, aesthetics, and environmental quality.

For detailed design, consult respective clauses (e.g., Clause 2.5, 3.7.6) and appendices.

Key Factors Governing Landscaping of Roads (IRC SP 21)

1. Main Factors (Clause 2.1):

   • Topography: Road alignment should follow natural landforms to minimize earthwork and preserve scenic beauty.
   • Environment: Protect existing vegetation, wildlife habitats, and water bodies.
   • Climate: Choose plant species suitable for local climatic conditions (temperature, rainfall, wind).
   • Operational Considerations: Ensure landscaping does not obstruct visibility or road safety.

2. General Guidelines:

   • Align roads to enhance traveler experience (e.g., along coastlines with selective tree groups for views, Clause 8.7.1).
   • Avoid sudden exposure of trees to sun and wind by gradual thinning and staged plantation (Desirable method).
   • Use selective pruning to create vistas and screen undesirable views (Fig. 28).

3. Sections Overview (Clause 1.8):

   • Sections 2 & 3: General landscaping considerations.
   • Sections 4 & 5: Rural and urban landscaping specifics.
   • Section 6: Highway structures.
   • Section 7: Road safety and amenities.
   • Section 8: Special areas (waterlogged, sandy).
   • Section 9: Existing roads improvement.
   • Section 10: Maintenance.
   • Section 11: Plantation guidelines.

Summary Table: Factors Affecting Landscaping

Recommended Plantation Stages (Desirable Method)

flowchart LR
    A[Initial Thinning of Forest] --> B[Simultaneous New Plantation]
    B --> C[New Plantation Matures]
    C --> D[Clear Central Portion for Road Construction]

For detailed species selection, slope protection, and maintenance, refer to Appendices I & II (pp. 66 & 74).

This approach ensures ecological balance, scenic enhancement, and road safety.

Highway Alignment & Cross-Section Design for Landscaping (IRC SP 21)

Key Specifications from Clause 2.5 & 4.3:

• Subgrade:

  • 500 mm selected earth with CBR × 5% for shoulder design.

• Typical Cross-Section (New 6 Lane Rural Alignment):

  • Refer Fig. 9 for detailed dimensions (all in mm).
  • Components: carriageway, shoulders, median, embankment slopes, cut slopes, drainage, roadside land.

• Plantation Density (per km):

  Sr.No	Rows	Number of Trees
  1	1st Row	333
  3	Total	499

• Landscape Considerations (Clause 4.3.1):

  • Cross-section design integrates roadside safety, aesthetics, and environmental factors.
  • Follow IRC:73-1980 for geometric elements; enhance with landscape-specific treatments.

Summary Table for Cross-Section Elements

Recommended Plantation Guidelines

• Use native species (Appendix I) for sustainability.
• Maintain spacing to allow growth and visibility.
• Ensure slope protection with vegetation (Appendix II).

flowchart LR
    A[Highway Cross-Section]
    A --> B[Carriageway]
    A --> C[Shoulders]
    A --> D[Median]
    A --> E[Embankment Slopes]
    A --> F[Drainage]
    A --> G[Roadside Plantation]
    G --> H[Tree Rows (333-499 trees/km)]
    E --> I[Slope Protection & Landscaping]

References:

• IRC SP 21 Clauses 2.5, 4.3
• IRC:73-1980

Key Points on Roadside Borrow Areas (IRC SP 21, Clause 4.9):

• Selection (4.9.2): Borrow areas should comply with IRC:10-1961, ideally hidden from highway view to minimize visual impact.

• Treatment (4.9.3):

  • Slope shaping: Cut faces must be flattened and corners rounded for aesthetics.
  • Drainage: Pit bottoms should slope toward natural outfalls to prevent water stagnation.
  • Landscape use: Large borrow pits can be converted into water bodies as landscape features.

Recommended Treatment Specifications

Summary Diagram: Borrow Area Treatment

flowchart TD
    A[Borrow Pit Excavation] --> B[Cut Faces Flattened & Rounded]
    B --> C[Pit Bottom Sloped Towards Outfall]
    C --> D{Large Pit?}
    D -- Yes --> E[Convert to Water Feature]
    D -- No --> F[Landscape & Vegetate]

Note: Refer IRC:10-1961 for detailed borrow area selection criteria and IRC SP 21 Clause 4.9 for treatment guidelines.

IRC SP 21: Road Land Width and Right-of-Way (ROW) Considerations

Key Specifications:

• Rural Areas (Clause 4.1 & 4.1.1):

  • Land width should be liberal and feasible for current and future needs.
  • Considerations:
    • Stable side slopes for cut/fill sections.
    • Contouring in deep cut/high fill areas.
    • Wider median in dual carriageways to avoid headlight glare.
    • Inclusion of plantations and scenic spots.

• Urban Areas (Clause 5.2 & 5.2.1): Factors influencing ROW width:

  • City zoning/master plan compliance.
  • Road functional classification (arterial, local, etc.).
  • Present & future traffic volumes.
  • Space for service roads, footpaths, cycle tracks, medians.
  • Provision for utilities (under/over-ground).
  • Environmental and landscape needs (noise barriers, plantations).
  • Open space for recreation.
  • Land acquisition cost.

Typical Considerations Table (Summary)

Conceptual Diagram of ROW Components

graph LR
  A[Right-of-Way] --> B[Carriageway]
  A --> C[Median / Central Verge]
  A --> D[Footpaths / Cycle Tracks]
  A --> E[Service Roads]
  A --> F[Utilities & Drainage]
  A --> G[Landscaping / Noise Barriers]

Summary:
ROW width must balance engineering, environmental, and socio-economic factors, with rural roads emphasizing earthwork stability and urban roads focusing on multifunctional space for traffic, services, and environment.

IRC SP 21: Key Specifications for Bridges, Approaches & Tree Guards

1. Bridges and Approaches (Clause 6.1)

• Subgrade Preparation:
  • Use 500 mm selected earth with CBR ≥ 5% for subgrade under approaches and shoulders.
• Shoulders:
  • Refer Table 4.5 for shoulder dimensions based on traffic and road width.
• Typical Cross-Sections:
  • For 6-lane rural roads, earthen shoulders and selected material layers are specified (see Fig. 9).
  • For 4-lane rural roads, similar layering with adjusted dimensions (see Fig. 8).

2. Tree Guards and Planting (Clause 3.7.6 & Section 11)

• Tree Planting Density:

  Sr.No	Rows	Number of Trees/Km
  1	1st Row	333
  3 or 4	Total Rows	499 (6-lane) / 583 (4-lane)

• Plant Spacing:
  • Plant-to-plant distance ~ 12 m (equivalent unit).
• Tree Guards:
  • Refer Section 11 for detailed roadside arboriculture guidelines, including guard dimensions and materials.

Summary Table: Typical Cross-Section Layers

flowchart TD
    A[Roadway] --> B[Carriageway]
    B --> C[Shoulder (Selected Material)]
    C --> D[Subgrade (500 mm, CBR≥5%)]
    A --> E[Tree Rows along Shoulder]
    E --> F[Tree Guards as per Section 11]

For detailed design, always cross-check with IRC SP 21 Section 11 for arboriculture and Clause 6.1 for structural details.

Truck Parks & Rest Areas Landscaping (IRC SP 21)

Key Specifications:

• Location: Near check barriers, interstate borders, or conventional truck stops.
• Space: Ample parking space with big trees for shade.
• Vegetation: Hardy trees and shrubs; green pockets to break large paved areas.
• Surface: Combination of paving and grassing to reduce maintenance.
• Screen Planting: To insulate truck parks from highway noise and dust.

Tree Planting (Clause 3.7.6 & Section 11):

• Plant-to-plant distance: Typically 3m to 12m depending on species and layout.
• Number of Trees per km (4-lane rural):

• Tree types: Hardy, drought-resistant native species (see Appendix I).

Layout:

• Refer to Figs. 23 & 24 for truck park layout and screen plantation.
• Rest areas layouts are shown in Figs. 20, 21, 22.

Maintenance:

• Regular pruning and watering.
• Use hardy species to reduce upkeep.

flowchart LR
    A[Truck Park Location] --> B[Ample Parking Space]
    B --> C[Big Trees for Shade]
    B --> D[Green Pockets]
    B --> E[Paving + Grassing]
    E --> F[Reduced Maintenance]
    C --> G[Hardy Tree Species]
    D --> G
    G --> H[Screen Planting]
    H --> I[Noise & Dust Insulation]

For detailed species and spacing, refer to Section 11 and Appendix I of IRC SP 21.

IRC SP 21: Landscaping in Special Areas (Coastal, Waterlogged, Saline, Marshy Zones)

Key Specifications & Guidelines

1. Waterlogged Areas (Clause 8.4 & 8.4.4)

• Plant Selection: Use species tolerant to waterlogging, low maintenance, and capable of reducing water table.
• Plantation Scheme: Refer to Section 11 for detailed species list and spacing.
• Soil Preparation: Improve drainage by raised beds or mounds.
• Maintenance: Minimal, focusing on survival in saturated soils.

2. Coastal Highways (Clause 8.7)

• Use salt-tolerant species to withstand saline spray.
• Employ windbreaks and dune stabilization plants.
• Protect embankments with vegetation to prevent erosion.

Typical Plant Characteristics for Special Areas

General Formula for Plant Spacing (Section 11 reference)

[ S = \sqrt{\frac{A}{N}} ]

Where:

• (S) = spacing between plants (m)
• (A) = total plantation area (m²)
• (N) = number of plants

flowchart LR
    A[Special Area] --> B[Waterlogged]
    A --> C[Coastal]
    A --> D[Saline]
    A --> E[Marshy]
    B --> F[Water-tolerant Plants]
    C --> G[Salt-tolerant Plants]
    D --> G
    E --> F

Summary: Select species adapted to local soil and water conditions, ensure proper spacing, and use vegetation to stabilize soil and control water levels as per IRC SP 21 guidelines.

Improving Landscape of Existing Roads (IRC SP 21, Clause 9, p.36)

Key Guidelines:

• Selective Thinning & Planting:

  • Thin existing forest along the road gradually to prevent wind damage and sunburn to remaining trees.
  • Simultaneously plant new trees on the roadside to maintain greenery and avoid abrupt exposure.

• Stage-wise Tree Management:

  • Stage 1: Thin forest and plant new trees.
  • Stage 2: Once new plantation matures, clear central portion for road construction.

• Visual Access & Screening:

  • Use selective pruning to expose scenic spots and open vistas below eye level without removing all trees.
  • Dense plantations can screen private or undesirable views.

Important Considerations:

• Align roads to maximize natural scenery (e.g., sea coast) without disturbing surroundings.
• Avoid placing roads too close to sensitive areas like waterlines.

Typical Process Flow (Mermaid Diagram):

flowchart TD
    A[Existing Dense Forest] --> B[Selective Thinning Along Road]
    B --> C[Simultaneous New Plantation]
    C --> D[New Trees Mature]
    D --> E[Clear Central Portion for Road]
    E --> F[Final Road with Improved Landscape]

Reference Tables & Figures:

• Fig. 27: System of felling trees in forest area (gradual thinning)
• Fig. 28: Selective pruning to expose vistas

This approach ensures environmental sustainability, roadside aesthetics, and minimized ecological disturbance while upgrading existing roads.

Safety and Visibility Considerations in Plantation (IRC SP 21)

Key Specifications (Clause 11.19 & 11.14):

• Survival Percentage:

  • Minimum 90% survival at any time for ornamental plants (except last row).
  • Shade plants (last row) should have 90% survival after replacements in first 2 years, then 80% afterwards.

• Spacing and Pit Size for Shade Plants:

  Parameter	Value
  Distance between rows	3.0 m
  Spacing between plants	8-12 m (or 6 m if high mortality expected)
  Pit size	60 × 60 × 60 cm

• Plant Density:

  • About 84 plants/km at 12 m spacing, or 167 plants/km at 6 m spacing.

• Sapling Height at Planting:

  • Greater than 2 m to ensure visibility and quick canopy development.

Safety & Visibility Guidelines:

• Maintain adequate spacing to avoid obstruction of driver sightlines.
• Use low-height ornamental plants near carriageway edges; tall shade trees in last rows.
• Ensure regular maintenance and replacement to keep survival above 90%.
• Avoid dense plantations near critical visibility zones like intersections and curves.

Typical Plantation Layout (Cross-section for 4-lane rural highway):

graph LR
A[Carriageway] --- B[Earthen Shoulder (selected material)]
B --- C[1st Row: Ornamental Plants (333 trees/km)]
C --- D[Subsequent Rows: Shade Trees (total 583 trees/km)]

This layout ensures safety by balancing tree density with driver visibility.

Summary:

• Follow 3 m row spacing, 8-12 m plant spacing.
• Use 60 cm³ pits for healthy growth.
• Maintain >90% survival to ensure consistent visibility and safety.
• Design plantations considering clear sight distances per IRC guidelines.

IRC SP 21: Tree Species Selection & Plantation Practices

Key Specifications & Tables

Additional Guidelines:

• In alkaline soils, break kankar panes using an augur.
• In waterlogged areas, create mounds with height adjusted to water level.
• Survival percentage after first 2 years reduces to 80%.

Summary Diagram:

flowchart LR
    A[Select Tree Species] --> B[Prepare Pit 60x60x60 cm]
    B --> C{Soil Condition}
    C -->|Alkaline| D[Break kankar panes]
    C -->|Waterlogged| E[Create mounds]
    D --> F[Plant Saplings > 2m Height]
    E --> F
    F --> G[Spacing: Rows 3m, Plants 8-12m]
    G --> H[Monitor Survival: 90% initially, 80% later]

This ensures healthy, sustainable plantation aligned with IRC SP 21 standards.

Key Specifications & Guidelines from IRC SP 21 for Pruning, Maintenance, and Protection

1. Pruning (Clause 11.23.1.2)

• Purpose:

  • Encourage vigorous growth (air, light, nutrients)
  • Remove overcrowded, weak, dried, diseased, pest-infested branches
  • Regulate flowering/fruiting

• Tools: Pruning knife, saw, shears, tree pruner

• Care: Avoid bark damage

• Timing:

  • Major pruning in dormant season: Dec-Jan & May-Jun
  • Light pruning anytime for safety/sanitation

• Method:

  • Retain framework, cut shoots to shape
  • Remove sick, thin, intertwining twigs
  • Avoid cutting 6-8 month old flowering buds indiscriminately

2. Maintenance Measures (Clause 11.22.1)

• Maintain fencing (barbed wire or others)
• Periodic pruning to prevent branch spread onto carriageway
• Replace dead plants before monsoon
• Weed clearing in grassed areas
• Remove dry leaves in summer (fire hazard)
• Watering during peak summer

3. Planting Densities & Layout (Clause 3.7.6 & Fig. 8)

Summary Table: Pruning Timing & Purpose

flowchart TD
    A[Plant Growth] --> B{Pruning}
    B --> C[Remove weak/diseased branches]
    B --> D[Shape & size control]
    B --> E[Encourage flowering]
    F[Maintenance] --> G[Fencing upkeep]
   

Plantation Activity Scheduling & Seasonal Considerations (IRC SP 21)

Key Points from Clause 11.20:

• Plantation activities must align with seasonal climatic conditions, especially monsoon timing.
• Ideal start: Onset of monsoon; if irrigation available, summer planting is beneficial due to high temperatures.
• Plants require 450-650 litres water/plant/year for 6-7 years until roots develop.

Table 5: Activity Schedule for Avenue/Median Plantation

Specifications (Clause 1.5)

Water Requirement Formula (Approximate)

[ \text{Water per plant/year} = 450 \text{ to } 650 \text{ litres} ]

• Adjust frequency based on

IRC SP 21: No Plantation Zones & Clearance Requirements

1. No Plantation Zone (Clause 11.26)

• No plantations are allowed within the clearance zone adjacent to the carriageway to avoid root damage and ensure safety.
• Typically, this zone is kept free of trees to prevent obstruction and damage to road infrastructure.

2. Plantation Specifications (Clause 11.19 & Table 11.14.1)

3. Typical Cross Section (Clause 3.7.6)

• Rows and Trees per km:

• Planting is done beyond the earthen shoulder and subgrade zones to avoid damage.

Summary Diagram: Plantation Zones Along Road

graph LR
A[Carriageway] --> B[Earthen Shoulder]
B --> C[No Plantation Zone (Clearance)]
C --> D[Plantation Zone (Trees planted)]
D --> E[Outer Boundary]

Key Takeaway: Maintain a 3 m row spacing, 8-12 m plant spacing, and a no plantation zone adjacent to the road to ensure safety and longevity of plantations per IRC SP 21.

IRC SP 21: Annexures - Suitable Trees for Various Regions

Key Specifications (Clause 1.5)

• No Plantation Zone: Within 1.5 m from carriageway toe.
• Median Cut & Grade Separator: Leave 5 m blank for traffic visibility.
• Curves: Ensure Stopping Sight Distance (SSD) = 170 m for 100 km/h design speed; avoid dense/tall trees on inner lanes.
• Median: Avoid medium/large trees prone to cyclone damage and root damage.
• Screen Plantations: Recommended near schools, hospitals, residential areas.

Annex A: Trees for Arid & Dry Regions (South Haryana, Rajasthan, Gujarat, Maharashtra, Central Plateau)

Annex B: Trees for Temperate & Sub-Tropical Areas (NW India, J&K, Himachal)

• Cedrus deodara (Deodar)
• Pinus sp. (Chir Pine)
• Juglans regia (Walnut)
• Taxus baccata (Yew)
• Grevillea robusta (Silver Oak)

Annex C: Trees for Indo-Gangetic Plains (UP, Punjab, Bihar, WB)

• Albizzia lebeck (Siris)
• Butea monosperma (Palash)
• Dalbergia sissoo (Sheesham)
• Syzygium cumini (Jamoon)
• Terminalia arjuna (Arjun)

Plantation Guidelines (Clause 11.9.1 & 11.10.1)

• 1st Row Trees: Use ornamental/shade species based on soil type.