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6. A Framework for Quantifying Reach-Scale Hydraulic Roughness in Mountain Headwater Streams.

Author

Kim, Tae-Hyun, Lee, Jeman, Kim, Taehyun, Choi, Hyung Tae, and Im, Sangjun

Subjects
FLOW velocity, GRAIN size, RIVER channels
Abstract

The presence of macroroughness elements directly affects the flow velocity in mountain headwater streams. Hydraulic roughness is the dominant resistance to flow caused by objects protruding into the water, but it is not measurable in the field. This study quantified the reach-average hydraulic roughness based on the channel morphology in two mountain streams. The average flow velocities of the reaches were measured using the dye-tracing method. The magnitude of the hydraulic roughness was derived from the grain size of the streambed materials (D50 and D84) and the cross-sectional/longitudinal bed roughness. The observations for low flows (0.04–0.43 m2/s discharge per unit width) indicated that the longitudinal 90% inter-percentile range ( I P R 90 L ) seemed to have considerable merit in examining the influences of large roughness elements on flow conveyance. A dimensionless hydraulic geometry relation that can reflect the field measurements over a limited range of hydraulic characteristics was also developed for estimating the reach-average flow velocity in steep and rough streams. Thus, the research framework used appears to provide a reliable method of quantifying reach-average hydraulic roughness from local data in mountain headwater streams. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Climate Elasticity of Annual Runoff: Observation in Fifteen Forested Catchments on a Latitudinal Gradient in East Asia

Author

Tanaka, Nobuaki, primary, Lai, Yen-Jen, additional, Im, Sangjun, additional, Mahali, Maznah Binti, additional, Tuankrua, Venus, additional, Kuraji, Koichiro, additional, Cleophas, Fera, additional, Tantasirin, Chatchai, additional, Gomyo, Mie, additional, Tseng, Chun-Wei, additional, Shiraki, Katsushige, additional, Hotta, Norifumi, additional, Asano, Yuko, additional, Inoue, Hiroki, additional, and Nainar, Anand, additional

Published
2023
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25. Restoration of Degraded Natural Limestone Forests in Cat Ba Biosphere Reserves, Vietnam

Author

Long, Tran Hai, primary, Hung, Trieu Thai, primary, Im, Sangjun, primary, Ha, Dang Thi Hai, primary, Khuong, Ninh Viet, primary, Tuan, Nguyen Van, primary, Son, Hoang Thanh, primary, Quy, Tran Hoang, primary, Bon, Trinh Ngoc, primary, Nguyen, Tran Cao, primary, Trung, Phung Dinh, primary, Binh, Tran Nam, primary, Lien, Le Hong, primary, and Li, Qiwen, primary

Published
2021
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32. Examining the impact force of debris flow in a check dam from small-flume experiments

Author

Eu, Song and Im, Sangjun

Subjects
Impact force, debris flow, Flume experiment, Structure design
Abstract

Debris flow is one of the most hazardous disasters in mountain regions of Korea. Rainfall-induced debris flows have occurred more frequently during past decades due to climate changes. Especially, its threat on many lives and properties in urban or suburban areas have increased. To control debris-flow disaster, check dams have been constructed in forest watersheds since 1985. Although check dams that recently constructed in Korea are expected to function as debris-flow barriers, impact force has not been considered during design procedure. For effective structure design regarding debris-flow disaster, estimation of debris-flow impact force is necessary. Meanwhile, it is well known that impact force is closely related to the flow characteristics of debris flow. In this study, small flume experiments were conducted to analyze the influence of flow characteristics to impact force of debris flow. Flume slope, total volume, and viscosity of mixture were selected as experiment variables. As a result, faster flow velocity was observed on steeper channel slope and larger mixture volume condition. In terms of viscosity, sediment-water mixture flowed faster as the viscosity becomes lower. The effect of flume slope on flow velocity was different as the viscosity of mixtures. However, flowing depth was correlated only to total mixture volume. Impact force was positively correlated to flow velocity and flow depth. By comparing various impact force estimation model, the hydrodynamic model has been selected for the best method to appropriately calculate the design impact force for check dams in small forested watersheds.

Published
2019
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33. Considering resources beyond water: Irrigation and drainage management in the context of the Water-Energy-Food Nexus

Author

Avellán, Tamara, Ardakanian, Reza, Perret, Sylvain, Ragab, Ragab, Vlotman, Willem, Zainal, Hayati, Im, Sangjun, and Gany, Hafied A.

Subjects
S01 - Nutrition humaine - Considérations générales, Eau d'irrigation, Objectifs de développement durable, P11 - Drainage, services écosystémiques, Évaluation impact sur environnement, sécurité alimentaire, F06 - Irrigation, Consommation d'énergie, Irrigation
Abstract

While the world is facing unprecedented transitions and threats we need to deeply rethink the relationships between water and energy use, food production, and ecosystem protection. This includes the development and deployment of ambitious, out‐of‐the‐box solutions towards sustainable development. This paper is based upon recent discussions before and during the 2nd World Irrigation Forum in Chiang Mai, Thailand. This paper takes stock of current knowledge and analyses the most recent trends in water, irrigation and the environment. It discusses the requirements for strategic approaches and the contributions of irrigation and drainage to Sustainable Development Goals. Firstly, we concentrated on renewed and more balanced relationships between water, energy, food and ecosystems in the context of irrigation and drainage management. Secondly, we assessed the positive and negative impact of agricultural water use in order to demonstrate and improve its performance. Given exacerbated competition and water resource scarcity, a better understanding of the positive effects and valuable ecosystem services provided by irrigation and drainage systems could pave the way to maximizing benefits and safeguarding the environment. Lastly, we tried to address the role of stakeholders in irrigation governance. This includes active contribution to policy‐making and planning, incentives, and most importantly, capacity development.

Published
2018

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