Damon Edward Abdi

Precipitation can inundate existing drainage infrastructure, putting communities throughout Louisiana at risk when flash floods or slow, relentless rains occur. Ongoing research at the LSU AgCenter is developing solutions to soak up this stormwater with style. Green infrastructure features such as rain gardens offer both engineering and aesthetics to support sustainable landscapes.

What Is a Rain Garden?

There are many examples throughout Louisiana, ranging from coincidentally installed plants in a ditch to sometimes complexly constructed features. Quite simply, it can be any low-lying area of the landscape that periodically pools with water after rain events, possesses plants that prefer more saturated soils, and sequesters and drains stormwater deeper into the soil.

More advanced rain gardens may possess subsurface drain systems to evacuate excess water and facilitate faster drainage; soils engineered to retain, treat and drain runoff water with more control; and creative compositions of plant materials to provide a wider array of ecosystem services and visual value.

Targeted Research to Address the Issues

At the LSU AgCenter Hammond Research Station (HRS), laboratory-scale research projects investigate and optimize media for rain gardens. Media can be optimized to support ornamental plant growth and remove contaminants through a variety of natural processes including bacterial transformations and adsorption (binding contaminants in soils).

Nitrogen and phosphorus are essential elements for plant growth, which is, why it is applied as fertilizer; however, they may also be considered contaminants if runoff water washes these nutrients from farm fields and landscapes to downstream waters. Rain gardens can be optimized to remove nitrogen by adding organic carbon materials to the media, retaining the runoff and providing sufficient time (several hours to a few days) for bacteria to denitrify and transform nitrogen. Phosphorus removal involves “binding” it to a charged surface such as clay or shale aggregate.

Of course, plants provide a vector for nutrient uptake from runoff-rich water for their own nutrition. A wide range of locally sourced materials, including organic byproducts like sugarcane bagasse and inorganic materials, such as sands and aggregates from regional industries, have been studied at a small scale to qualify and quantify their potential for use in larger rain garden systems. These studies indicate that rain garden media can be optimized for nitrogen removal (more than 90% in under two days) if water is retained in a carbon-rich medium.

Scaling Solutions for Real-World Results

Building upon the laboratory-scale research, field-scale rain gardens were developed to represent real-world dimensions. A total of 36 model plots (measuring 10-by-10 feet each) that could fit between crosswalks, street corners and other congested sites were developed at the HRS.

Plots were excavated and filled with unique rain garden media, including combinations of standard landscape bed materials (pine bark and sand) with woodchips and expanded shale aggregate based on lab-scale studies. A mix of Louisiana native plants suitable for a spectrum of soil moisture conditions was installed in the different media, including bald cypress (Taxodium distichum), sweetbay magnolia (Magnolia virginiana), river birch (Betula nigra) and Virginia willow (Itea virginica).

An on-site weather station and soil moisture sensors (in each of the 36 individual plots) measure all the rain that falls and how fast it drains or evaporates from each medium. This research provides direct insights toward which rain garden media and plant species work best for a wide range of conditions.

By using installations of representative size, community members and green industry professionals alike can draw direct inspiration in their own designs.

Implementing Actionable Solutions for Louisiana Communities

Rain gardens may be optimized to meet the unique community needs throughout Louisiana. Rural and suburban communities may benefit from rain garden installations that can remediate fertilizer-rich runoff from agricultural lands, home lawns and landscapes. The plurality of paved surfaces in urban areas reduces the rate at which water can naturally infiltrate into surrounding soils, demanding rapid drainage to reduce flooding risks. For areas like parking lots, rain gardens may be optimized to facilitate fast drainage, regardless of how small a footprint is provided for planting.

The LSU AgCenter is combating community concerns surrounding flooding by using rain gardens engineered for a variety of conditions. Through a combination of lab-scale research to better understand the underlying mechanisms of rain garden media, field-scale plots to provide a tangible template in real-world conditions and offering advice to stakeholders and residents of Louisiana through extension resources, the LSU AgCenter is advancing sustainable solutions for the Louisiana landscape.

Damon Edward Abdi is an assistant professor of landscape horticulture at the LSU AgCenter Hammond Research Station.

This article appears in the spring 2026 edition of Louisiana Agriculture.

Rain gardens provide interest to people and pollinators when in bloom. Photo by Damon Abdi

A close-up view shows several field-scale rain garden research plots at the LSU AgCenter Hammond Research Station. Photo by Damon Abdi

An overhead view of the 36 field-scale model rain gardens at the LSU AgCenter Hammond Research Station. Photo by Brianna Slade