Hurricane season: how does extreme weather affect soil? (ASK Around)

If you live anywhere along the East Coast, you know that June through November is hurricane season: that time of year when Sandy, Harvey, Ian, and Maria aren't just names of friendly neighbors but of powerful and destructive storms. The effects of strong winds and heavy rains above ground are clear -- but how do they affect our soil?

One of the biggests risks to soil from extreme weather is erosion. Both heavy rains and high-speed winds can strip away nutrient-rich topsoil, leaving behind the less fertile subsoil underneath. Erosion destroys soil structure and can leave weak or hardened soils that have poor air and water infiltration, are difficult for roots to penetrate, and have low organic matter content. For costal areas, the counterpart to huricanes eroding beaches is the deposition of sand elsewhere, requiring great effort to restore both the beaches and the properties affected by the sand overwash by moving it back. To decrease erosion in yards and home gardens, there are many protective measures that land managers can take, such as keeping the ground covered with living roots that hold soil in place rather than leaving it bare. But they may be no match for a hurricane.

Besides erosion, heavy rains can speed up nutrient leaching and deplete the soil of essential plant nutrients, especially nitrogen. As water moves down through the soil after heavy rain or a flood, it can take nutrients, organic matter, and small minerals with it. Over time, this leaves the soil lighter/paler in color, more sandy, and less fertile. Nitrogen is particularly vulnerable to loss depending on the weather, because it can be leached down out of the soil by percolating water or be release as a gas into the atmosphere through denitrification, a chemical reaction carried out by bacteria especially in water-logged soils. Nutrient leaching is one reason why SoilKit typically recommends spliting up fertilizer treatments throught the growing season -- heavy rains can't wash out nutrients from your soil if they're still safely stored in your shed! 

Flooding/innundation due to severe weather can negatively impact soil and plant health by dramatically changing the soil ecosystem, down to the microscopic level. A soil is considered waterlogged when the natural pore spaces in the soil matrix become completely filled with water, in contrast to the normal balance of around 50% water and 50% air. This results in poor gas exchange with the atmosphere and very low levels oxygen in the soil, leading to suffocation of plant roots and a completely different environment for soil microbes. Anaerobic (oxygen-free) conditions are hospitable for bacteria that  produce greenhouse gases such as methane and nitrous oxide. At the same time, many beneficial soil microbes are unable to thrive without oxygen.

Specifically along the coasts, extreme weather events like hurricanes can lead to soil salinization due to salt water intrusions in a storm surge. As a recent example, storm surges from hurricane Milton in October 2024 lead to severe salt water intrusions in Sanibel Island, FL, that disrupted freshwater ecosystems. Remediating a saline soil for use in agriculture or growing a healthy lawn poses a challenge that can take years to accomplish.

Are there any positive impacts that hurricanes can have on soil? In some cases, heavy rains from storms can stir up sediment from riverbeds and redistribute it in the surrounding land, adding nutrients to depleted soils. This is why floodplains where silt is regularly deposited are known as highly fertile areas. However, these benefits are usually localized and depend heavily on the characteristics of the landscape and the specifics of the storm.

Has your yard been impacted by severe weather this year? SoilKit is here with science-backed testing and advice to help restore and protect your soil!