都市流域における洪水リスク軽減：グレー・自然基盤・ハイブリッド戦略アプローチからの知見
Flood risk mitigation for an urban catchment: findings from a grey, nature-based solutions and hybrid strategy approach (原題)
Dennis Ndashiru Audu, Hosea M. Mwangi, John Mwangi
🤖 gxceed AI 要約
日本語
ナイロビ川流域を対象に、HEC-RASモデルでグレーインフラ、自然基盤ソリューション（NbS）、ハイブリッドの3つの洪水管理策を比較評価した研究。NbSはピーク流量を37〜75%削減しピークを約1時間遅延、グレーは洪水深を55〜60%削減したが流速を増加させた。ハイブリッドが最もバランスの取れた水理性能を示し、気候・開発圧力下の都市洪水リスク管理に統合的アプローチが有効と結論づける。
English
Using HEC-RAS, this study compares grey infrastructure, nature-based solutions (NbS), and a hybrid strategy for flood management in the Nairobi River Catchment. NbS cut peak discharge 37–75% and delayed peak flow ~1 hour; grey infrastructure reduced flood depth 55–60% but raised flow velocity. The hybrid approach delivered the most balanced hydraulic performance, supporting integrated engineered-plus-nature pathways for urban flood risk under climate pressure.
Unofficial AI-generated summary based on the public title and abstract. Not an official translation.
📝 gxceed 編集解説 — Why this matters
日本のGX文脈において
日本では都市型水害・流域治水が適応策の重要課題であり、グリーンインフラと灰色インフラの統合評価は国土交通省の流域治水政策や企業の気候リスク適応（TCFD適応編）に示唆を与える。ただし対象はケニアであり、日本の開示・政策への直接的連動は限定的。
In the global GX context
As adaptation gains weight in TCFD/ISSB-aligned climate risk disclosure, this paper offers quantitative evidence that hybrid grey-plus-NbS strategies outperform single approaches—useful for physical-risk assessment and adaptation planning in disclosure frameworks, though the evidence is from a single Global South catchment.
👥 読者別の含意
🔬研究者:都市洪水モデリングにおけるNbSとグレー・ハイブリッドの水理性能比較の実証的手法として参照できる。
🏢実務担当者:物理的気候リスク評価や適応投資の検討において、自然基盤と工学の統合策の定量的便益を把握できる。
🏛政策担当者:都市洪水適応政策において、単一策ではなく統合的アプローチを優先する根拠として活用できる。
📄 Abstract（原文）
ABSTRACT Flow diagram showing rainfall-driven flood modelling using HEC-RAS, comparing baseline, nature-based solutions, structural measures, and hybrid scenarios, with reductions in flood depth, velocity, and discharge across the catchment. Rapid urban expansion and informal settlements are increasing exposure to flood hazards in urbanising catchments such as the Nairobi River Catchment. The 2024 El Niño event caused widespread flooding, affecting critical infrastructure and highlighting the urgent need for effective mitigation strategies. This study evaluates three flood management approaches using the HEC-RAS model: (1) modified channels as grey infrastructure, (2) soil organic matter enhancement and reforestation as Nature-based Solutions, and (3) a hybrid strategy. Model performance showed strong agreement with observed flows (R2 = 0.88; NSE = 0.75). Spatial datasets, including Global Forest Change and Land Productivity Dynamics, were used to identify intervention zones and parameterise scenarios. Results show that NbS reduced peak discharge by 37–75% and delayed peak flow by about one hour. Grey infrastructure achieved the greatest impact, reducing flood depths by 55–60% and peak discharge by 48–75%, but increased flow velocities. The hybrid strategy provided the most balanced hydraulic performance, combining runoff attenuation with improved channel conveyance to deliver consistent reductions in flood magnitude and enhanced flow regulation. These findings demonstrate that integrated approaches combining engineered and nature-based interventions offer a resilient pathway for managing urban flood risk under increasing climatic and developmental pressures.
🔗 Provenance — このレコードを発見したソース
- openalex https://doi.org/10.2166/wcc.2026.484first seen 2026-11-08 05:00:41 · last seen 2026-11-14 05:07:52
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