INVESTIGATING PALAEOMEGAFLOOD SEDIMENTATION INFLUENCES ON VINEYARD SOILS IN SUNNYSLOPE, ID, SNAKE RIVER VALLEY

Terroir is the set of factors including climate, soil, and management practices that influence the character of a wine, thus relating the physical conditions of grapevine growth to the sensory attributes of the finished product. Among the physical factors, the soil environment (texture, chemistry, organic carbon) is a major influencer of wine grape quality. Soil texture influences the storage and availability of water and plant-available nutrients that affect the growth pattern of the vine and grape maturation. The chemistry of the soil includes pH as well as the elements that are bioavailable, and organic carbon further influences water-holding capacity.

The Sunnyslope District (Sunnyslope) of the Snake River Valley Wine Region is located adjacent to the Snake River between Melba, ID and Adrian, OR. Approximately 14.5 ka, floodwaters from the outburst of Pleistocene Lake Bonneville flowed through the Snake River, flooding near-by reaches including Sunnyslope. However, any connection between the Bonneville Flood (the flood) and modern agricultural soils in Sunnyslope has yet to be examined. This study investigates whether the flood and subsequent inundation of portions of Sunnyslope had an influence on current variability in soil environment factors in vineyards. This study combines field excavation and analyses of soil texture and chemical composition to characterize the soils in selected vineyards. Preliminary soil texture analysis of vineyard soil samples from within the mapped inundation zone suggests deposition of sands and gravels over a preexisting (now buried) surface. Ongoing vineyard soil sampling and lab analyses will investigate further any connection between the Sunnyslope vineyard soils and the flood. Through investigating the variability of soil factors, vineyard owners will have better information to manage vineyards for the production of high-quality grapes and desirable wines reflecting the conditions under which they were grown, the terroir.