Retention of sediments and nutrients in buffer zones with different riparian vegetation

In Norway, eutrophication is a major problem for freshwater quality, mainly due to excess phosphorus (P) inputs from agricultural areas. Hence, vegetated buffer zones along water bodies have been used for decades to reduce soil and phosphorus losses from agricultural land to waterbodies. In Norway, buffer zones with grass production are the most popular since these are eligible for subsidies.

The efficiency of grass-covered buffer zones has previously been studied in areas with relatively steep slopes and high risk of surface runoff and erosion. However, more field-based knowledge is needed on the retention efficiency of grassed buffer zones in areas with gentle slopes. In addition, other functions of these zones such as reduced bank erosion, biodiversity, and food production, need to be explored. The latter is important since only 3% of Norway’s area is under cultivation.

Herein, we present the results of three years of monitoring and rainfall simulation experiments carried out along the Hobølelva River in SE Norway. Our aim was to investigate different functions of buffer zones, including the retention of nutrients and particles and the protection against bank erosion in buffer zones with different vegetation cover (grass, shrubs and trees). Results to be presented include comparisons of 1) retention of nutrients and soil practices as observed during a series of rainfall simulation experiments in the field, 2) soil and hydrogeology characteristics (texture, porosity, hydraulic conductivity, infiltration capacity etc.), and 3) stream bank hydrogeological monitoring and stability estimation under different vegetation.