Short‐term erosion rates from a 7 Be inventory balance

Detailed soil erosion studies benet from the ability to quantify the magnitude of erosion over time scales appropriate to the process. An inventory balance for 7 Be was used to calculate sediment erosion in a 30·73 m 2 plot during a series of runoff‐producing thunderstorms occurring over three days at the Deep Loess Research Station in Treynor, Iowa, USA. The inventory balance included determination of the pre‐ and post‐storm 7 Be inventories in the soil, the atmospheric inux of 7 Be during the event, and proles of the 7 Be activity in the soil following the atmospheric deposition. The erosion calculated in the plot using the 7 Be inventory balance was 0·058 g cm −2 , which is 23 per cent of the annual average erosion determined using 137 Cs inventories. The calculated erosion from the mass balance is similar to the 0·059 g cm −2 of erosion estimated from the amount of sediment collected at the outlet of the 6 ha eld during the study period and the delivery ratio (0·64). The inventory balance of 7 Be provides a new means for evaluating soil erosion over the time period most relevant to quantifying the prediction of erosion from runoff. Copyright © 2003 John Wiley & Sons, Ltd.