🌍🌧️ Approaches for LID Control Placement in Subcatchments

 🌍🌧️ Approaches for LID Control Placement in Subcatchments

Implementing Low Impact Development (LID) controls within a subcatchment can be approached in two distinct ways, each catering to different urban planning and environmental objectives:

1. Mixed LID Placement in Existing Subcatchment 🏞️🌳

• Method: Introduce one or more LID controls into an existing subcatchment. This displaces an equivalent non-LID area.
• Variety: Allows a mix of LIDs, each treating runoff from different non-LID areas of the subcatchment.
• Parallel Action: LID controls act in parallel, not in series. Meaning, outflow from one LID doesn't become inflow for another.
• Adjustments Needed: May require modifications to properties like Percent Impervious and Width to balance the area replaced by LIDs.
• Example: Transforming 75% of a 40% impervious area to permeable pavement changes the imperviousness to around 14.3%.
• Runoff Dynamics: LIDs like Green Roofs and Rooftop Disconnection treat only the precipitation directly falling on them, not capturing runoff from other areas.

2. Dedicated Single LID Practice in New Subcatchment 🌱🚧

• Approach: Create a new subcatchment entirely devoted to a single LID practice.
• Series Placement: Allows LID controls to be aligned in series and receive runoff from multiple upstream subcatchments.
• Subcatchment Adjustments: If carved out of existing subcatchments, modifications to Percent Impervious, Width, and Area properties might be necessary.
• Override Standard Properties: In a subcatchment fully occupied by an LID, standard surface properties are overridden by those specific to the LID.
• Routing Outflows: Surface and drain outflows from LIDs usually go to the same outlet as the parent subcatchment. Alternatives include routing all LID outflow back to the pervious area of the parent subcatchment or directing drain outflow to a separate outlet.

🔧💧 Implementation Considerations

• Spatial Planning: Deciding which approach to use depends on the spatial and environmental context of the subcatchment.
• Environmental Impact: Each method has different implications for water management, infiltration, and ecological impact.
• Urban Compatibility: Consideration of the urban landscape and existing infrastructure is crucial in selecting the appropriate method.

In conclusion, these two approaches offer flexible strategies for integrating LID controls into urban landscapes, each with its unique advantages and considerations. Proper planning and execution of these strategies can significantly enhance sustainable water management and ecological resilience in urban areas. 🏙️🌱🚰

🌿🌧️ Detailed Overview of LID Controls with Emojis

 🌿🌧️ Detailed Overview of LID Controls with Emojis

Low Impact Development (LID) Controls are innovative practices designed to manage surface runoff in an eco-friendly way. They aim to handle runoff through detention, infiltration, and evapotranspiration, much like Aquifers and Snow Packs. Here’s a detailed look at the various types of LID controls modeled in SWMM:

1. StreetPlanter 🌳🛣️:

   • Nature: Depression areas with vegetation in engineered soil above a gravel drainage bed.
   • Function: Stores, infiltrates, and evaporates direct rainfall and runoff from surrounding areas.

2. RainGarden 🌼🌧️:

   • Type: A variant of bio-retention cells, composed solely of an engineered soil layer, sans gravel bed.
   • Purpose: Simplified bio-retention for rainwater.

3. GreenRoof 🏠🌿:

   • Design: Soil layer on a drainage mat on roofs.
   • Benefit: Manages rainfall percolation and runoff on roof structures.

4. InfilTrench 🕳️💧:

   • Structure: Narrow ditches filled with gravel.
   • Role: Intercepts runoff, providing storage and time for soil infiltration.

5. PermeablePavement 🚗🌳:

   • Continuous System: Gravel-filled excavated areas with porous overlay.
   • Block Paver System: Impervious blocks on a gravel bed.
   • Advantage: Reduces surface runoff, promotes infiltration.

6. Cistern 🛢️🌦️:

   • Utility: Containers for collecting roof runoff.
   • Usage: Stores rainwater for later use or release.

7. Downspout 🏠🌧️:

   • Approach: Redirects roof downspouts to pervious areas instead of storm drains.
   • Effect: Encourages ground infiltration, reducing direct stormwater discharge.

8. VegSwale 🌾🌊:

   • Formation: Vegetated, sloped channels.
   • Impact: Slows runoff conveyance, enhances soil infiltration.

Additional Features and Considerations:

• Drain Systems Optional 🔄: Bio-retention cells, infiltration trenches, and permeable pavements may include drains in their gravel beds to manage excess runoff.
• Impermeable Floors/Liners 🚫💧: Prevent infiltration into native soil, ideal for specific site conditions.
• Clogging and Conductivity 🚧: Infiltration trenches and permeable pavements may experience reduced conductivity over time.
• Pollutant Removal 💧🧪: LID units with drains can be assigned removal percentages for pollutants.
• Runoff and Pollutant Reduction 🌍🌟: LIDs reduce both the volume of runoff and the mass load of pollutants due to decreased flow volume.

These LID controls represent a step forward in sustainable urban planning, offering a blend of ecological preservation and urban development. By implementing these systems, urban areas can significantly reduce their environmental footprint and contribute to a healthier, greener future. 🌳🏙️🌍