Expert opinion: uncertainties in hydraulic roughness

Water level predictions in rivers are used for a variety of purposes in water management. For example, designing flood defence measures and evaluating natural rehabilitation in flood plains, cannot be done without water level predictions. However, these water level predictions are uncertain and a major part of this uncertainty is caused by the uncertainty in the roughness coefficient (Van der Klis, 2003; Van Vuren, 2005). Hydraulic roughness in rivers results from (among others): grain roughness, form roughness and vegetation roughness. The roughness coefficient is uncertain because different elements creating the hydraulic roughness are uncertain (e.g. grain size, dune height). To quantify the influence of the uncertain roughness coefficient on water level predictions, we first need a quantification of the uncertainty in the roughness coefficient

Book Reviews

Obra ressenyada: John W. DARDESS, More Than the Great Wall : The Northern Frontier and Ming National Security, 1368-1644. Lanham, MD: Rowman & Littlefield, 2020.At over 550 pages, John Dardess' impressive swansong provides a lengthy and detailed overview of that perennial headache of Ming national security: the long, ever-unruly and perilous northern frontier. Mere stability was usually most the imperial leadership could hope for. Despite some offensive campaigns during the early empire, for most of the period under review in this book no attempt was made to expand political control into the steppe and frontier security was usually characterized by a reactive and defensive mindset. Applied policies were legion, but purely military measures occupied the prime position, making this overview a great contribution to military history

Review

Aftermath of the East Asian War of 1592-1598OBRA RESSENYADA: Yang Haiying 杨海英, Cong "Tang jiang shu tie" kan Ming-Qing shidai de nanbing beijiang 从《唐将书帖》看明清时代的南兵北将 (Southern Soldiers and Northern Generals during the Transitional Period of Ming & Qing: From the Perspective of Letters from Chinese Servicemen during Campaign in Korea), Beijing: Zhongguo shehui kexue chubanshe 中国社 会科学出版社, 2022. ISBN 978-7-5203-8941-9, 512 pages

Variations in roughness predictions (flume experiments)

Data of flume experiments with bed forms are used to analyze and compare different roughness predictors. In this study, the hydraulic roughness consists of grain roughness and form roughness. We predict the grain roughness by means of the size of the sediment. The form roughness is predicted by three approaches: Van Rijn (1984), Vanoni & Hwang (1967) and Engelund (1966). The total roughness values (friction factors) are compared with the roughness values according to the DarcyWeisbach equation. Results show that the different methods predict different friction factors. In future research uncertainties in the hydraulic roughness will be taken into account to determine their influence on the computed water levels

Securing the emperor, securitising the guns : the strangely delayed dissemination of Ottoman military technology in the late Ming empire

Aftermath of the East Asian War of 1592-1598 ProjectAjuts: Research and writing for this article were done while the author was a part of the European Research Council-funded Aftermath of the East Asian War of 1592-1598 project hosted by the Autonomous University of Barcelona. It is a European Research Council Starting Grant project (2018-2024) run by ICREA professor Rebekah ClementsThis article analyses the reasons behind the delayed appropriation and adoption of Ottoman harquebuses by the Ming army. Although these weapons had reached the empire by the mid-16th century, their existence was only acknowledged at the end of the century. Through the lens of securitisation, I will argue that this delay was a result of the context of Luso-Ottoman geopolitical rivalries in which these weapons were possibly leveraged as an incentive to form a Sino-Ottoman alliance against the Portuguese. I will argue that a civil bureaucracy averse to assertive activist rulership could have prevented the emperor from participating in the resulting military diplomacy. By comparing this event with a later Dutch East India Company embassy with similar geopolitical intentions, I will argue that the Ming civil officials achieved their goal by controlling the emperor's perception of Ottoman intentions. In terms of securitisation, this meant that the emperor himself was the main audience and his officials the securitising agents in matters of foreign relations