Springtime in Riparian Buffers: Flooded with Challenges and Opportunities

Springtime, for many, is a sign of new beginnings, especially as the weather turns and we spend more time outside. As temperatures begin to rise, snow on the ground melts, and our precipitation outlook turns from a chance of snow to the possibility of rain. This rain brings water that can recharge our soil and groundwater reserves for the upcoming growing season. In fact, the most recent rain in early March 2024 was enough to finally lift the drought watches and warnings in eight PA counties including Adams, Cameron, Clinton, Cumberland, Franklin, Fulton, Westmoreland, and York. For more information about drought tracking in Pennsylvania, please visit the Pennsylvania Department of Environmental Protection website for up-to-date information.

While groundwater recharge is the ideal situation with spring precipitation, there are times when precipitation and snowmelt can happen too fast for our soils to infiltrate. Flooding conditions can occur during these times of excess precipitation. This is especially the case for areas next to streams, called riparian areas. Riparian areas are typically characterized by higher groundwater levels and, therefore, wetter soil. When the stream floods this area, water ponding on the surface of the soil is typical over long periods of time. This sort of hydrology is natural.

Floods can also cause water levels in the stream to increase. More water flowing in the stream also means potential for stream bank erosion and property loss. For this reason, people with streamside properties all over Pennsylvania are planting what are called riparian buffers. Riparian buffers or "buffers" are streamside native vegetation plantings that can help anchor soil in place and help slow or stop property loss after flooding events. If you have additional questions about riparian buffers, please visit Penn State Extension's riparian buffer informational resources.

While riparian buffers are a great practice to help mitigate property loss during floods, these buffers can also be very sensitive to flooding, especially within the first 5 to 10 years after planting. Water moving across the surface of the soil during floods can remove loose soil and carry it downstream. This includes the soil around recently planted trees. If this happens, tree roots can be exposed, and the tree could be negatively impacted. Inspection and putting new soil in place after large flood events can help increase the chances of survival of young plantings.

While inspecting for signs of soil movement, it is also important to look for areas of water ponding on the surface of the soil. As stated earlier, this hydrology is common and natural in riparian zones, but the areas of ponding may not be obvious when the vegetation is planted. Most vegetation planted in riparian buffers are water-loving species, but some still cannot survive long periods of ponding and little to no oxygen in the soil around their roots. If ponding is spotted around vegetation for extended periods of time, that vegetation may become stressed. Examples of stress include symptoms similar to times of drought like leaf wilting, leaf and needle drop, and eventually death. Any young plant that shows signs of stress in ponded areas should be moved to a drier location to survive. These plants can be replaced by vegetation that is more suitable to these extended wet conditions.

An example of a tree that died due to extended ponding conditions. This area was too wet for this tree to survive the extremely wet conditions. Inspection of riparian areas after flooding can help prevent tree mortality. (Photo: Tyler Groh, Penn State)

Some additional items to look for after flood events in newly planted riparian buffers include tree shelter shifting and debris accumulation. Flood water has great energy and can shift or even push over any tree shelter that was placed around newly planted trees. It is important to stand those tree shelters back up and make sure they are placed firmly in the ground to ensure proper tree protection. Further, flood waters can carry debris like other vegetation from upstream or even human trash. This debris can get lodged on newly planted vegetation, potentially even being heavy enough to cause newly planted vegetation to lean. If not corrected, this can cause damage to the vegetation and potentially lead to mortality. Riparian buffer vegetation growth success can be enhanced by simply removing debris from vegetation after a flood. For more tips and tricks of riparian buffer maintenance, consider watching the Maintaining Streamside Plantings-Ensuring Successful Buffers webinar series.