Flood Mitigation - KCPM Engineering

KCPM Rain Fall Management & Flood Mitigation Design Solutions

1. Infiltration-Based Solutions (Improved dry well solution)

These manage water by letting it soak into the ground, but are designed to be safer and more effective.

Infiltration Trenches / Basins

Shallow, rock-filled trenches or depressed areas that store runoff and allow it to percolate into the soil. They have a larger surface area than a dry well and are easier to inspect and maintain.

Rain Gardens / Bioretention Cells

Shallow, landscaped depressions with special soils and water-tolerant plants. They filter pollutants biologically and chemically while allowing water to infiltrate. They are highly effective for managing runoff from roofs, driveways, and streets.

Permeable Pavements

Pavements made of porous concrete, porous asphalt, or interlocking pavers that allow water to pass through into a stone reservoir below, where it slowly infiltrates. Great for driveways, parking lots, and walkways.

2. Storage and Slow-Release Based Solutions

These capture runoff and release it slowly into the storm drain system or a waterway, preventing surges.

Detention Basins / Dry Ponds

These are landscape depressions (often in parks) that fill with water during a storm and release it over hours or days through a small outlet. They are "dry" between storms.

Retention Basins / Wet Ponds

These have a permanent pool of water and provide additional storage for stormwater runoff. They offer water quality benefits through settling and biological activity.

Cisterns & Rainwater Harvesting Tanks

Above or below-ground tanks that capture roof runoff. The water can be used for irrigation, washing, or (with proper treatment) household use. This prevents the water from becoming runoff at all.

Underground Storage Systems

Large-scale modular structures (like plastic crates or large pipes) buried underground to store massive volumes of runoff, which is then metered out. Common in urban redevelopment and commercial sites.

3. Conveyance & Evapotranspiration Solutions

These move water safely away or return it to the atmosphere.

Swales (especially Bioswales)

Grassy or vegetated channels that convey water while allowing some infiltration and filtering. Bioswales are engineered with specific soils and plants for enhanced treatment.

Green Roofs

A layer of vegetation planted over a waterproofing membrane on a roof. They absorb rainwater, reduce runoff, and provide insulation.

Constructed Wetlands

Engineered systems that mimic natural wetlands to treat and store stormwater runoff. They are excellent for large areas and provide significant ecological benefits.

4. Landscape-Based & "Slow the Flow" Solutions

These work with the land to reduce runoff at its source.

Soil Amendment & Restoration

Compacting soil during construction creates impermeable surfaces. Adding compost and tilling it in can dramatically increase an area's infiltration capacity.

Disconnection

Simply directing downspouts onto lawns, gravel spreader strips, or into rain gardens instead of the storm drain. It's the simplest, lowest-cost method to reduce runoff.

Terracing & Contouring

On sloped land, creating level planting areas or shaping the land to follow contours slows water flow and increases infiltration.

How to Choose the Right Alternative:

Goal

Is it for a single-family home (rain garden, cistern, permeable patio) or a large commercial site (detention basin, underground storage)?

Local Regulations

Many municipalities now have stormwater ordinances that favor or require green infrastructure. Check with your local Public Works or Planning

Soil Type

Infiltration solutions (rain gardens, trenches) only work well in soils with adequate percolation rates (not heavy clay). A percolation test is key.

Space Available

A wet pond needs space, while an underground storage system or a smaller rain garden can fit in tighter areas.

Budget & Maintenance

Cisterns and permeable pavement have higher upfront costs. Rain gardens and swales require periodic weeding and mulch replacement.

Key Modern Concept: Low Impact Development (LID) or Green Infrastructure

KCPM implements the modern approach and do not to rely on a single alternative, but to use a suite of these techniques across a site to mimic the natural water cycle. This is far more resilient and environmentally beneficial than traditional “pipe-and-pond” or dry well approaches.

In short: For a typical homeowner looking to replace a dry well, a rain garden (if soils allow) or a cistern for rainwater harvesting are often the most effective and beneficial alternatives. For larger projects, a combination of permeable pavement, bioswales, and underground storage might be the answer; but it is always best to consult a local civil engineer.