Strong increases in flood frequency and discharge of the River Meuse over the late Holocene: impacts of long-term anthropogenic land use change and climate variability

摘要

In recent years the frequency of high-flow events on the Meuse (northwestEurope) has been relatively great, and flooding has become a major researchtheme. To date, research has focused on observed discharge records of thelast century and simulations of the coming century. However, it is difficultto delineate changes caused by human activities (land use change andgreenhouse gas emissions) and natural fluctuations on these timescales. Toaddress this problem we coupled a climate model (ECBilt-CLIO-VECODE) and ahydrological model (STREAM) to simulate daily Meuse discharge in twotime-slices: 4000–3000 BP (natural situation), and 1000–2000 AD (includesanthropogenic influence). For 4000–3000 BP the basin is assumed to be almostfully forested; for 1000–2000 AD we reconstructed land use based onhistorical sources. For 1000–2000 AD the simulated mean annual discharge(260.9 m3 s−1) is significantly higher than for 4000–3000 BP (244.8 m3 s−1),and the frequency of large high-flow events (discharge >3000 m3 s−1) is higher (recurrence time decreases from 77 to 65years). On a millennial timescale almost all of this increase can beascribed to land use changes (especially deforestation); the effects ofclimatic change are insignificant. For the 20th Century, the simulatedmean discharge (270.0 m3 s−1) is higher than in any other centurystudied, and is ca. 2.5% higher than in the 19th Century (despitean increase in evapotranspiration). Furthermore, the recurrence time oflarge high-flow events is almost twice as short as under natural conditions(recurrence time decreases from 77 to 40 years). On this timescale climatechange (strong increase in annual and winter precipitation) overwhelmed landuse change as the dominant forcing mechanism.