Feasibility of Traditional Open Levee System for River Flood Mitigation in Japan

Abstract

An open levee system is a traditional flood mitigation system for reducing the expansion of inland flooding and decreasing the peak flow. However, there have been few quantitative studies on its feasibility. Furthermore, the differences in applicability depending on the topography and the construction of continuous levees have not been fully examined. We studied its feasibility based on simulations in the Kuji River area, where the vast Typhoon Hagibis occurred. Morphological models representing the past (the 1940s) and the present (2019), obtained by modifying the highly accurate digital elevation models (DEM) via the tracing of aerial photos, were applied to a 2D unsteady flow simulation model to reveal the effects of the levee system on river hydrography and overland flood behavior. The results indicated that inundation flow through an open area decreased both inundation duration and depth, while the reduction of peak discharge is relatively insignificant at approximately 10%. The sub levees are not adequate under the current conditions and floodwater volume, and their effectiveness depends on the surrounding conditions, such as the development of continuous levees.

Sociocultural Dimensions in Water Resources Management

“…Water can be retained when a flood occurs through discontinuous parts of a levee. The flooded areas can be used as farmland or paddy fields, because one purpose of open levee construction is to accumulate organic matter during floods (Teramura and Shimatani 2021), and it is also found that open levees can play a role in flood mitigation (Ohtsuki, Itsukushima, and Sato 2022).The introduction of an SFPA has potential to promote flood mitigation strategies utilizing open levees. In fact, before the introduction of modern technology of Western countries, flooded water in rural areas was not constrained within a river bank but freely inundated, which was the standard approach to mitigate flood damage (Takahasi 2012).…”

Experimental Investigation of Levee Erosion during Overflow and Infiltration with Varied Hydraulic Conductivities of Levee and Foundation Properties in Saturated Conditions

“…River levees play a vital role in global flood protection efforts by acting as crucial barriers against increasingly frequent and intense extreme weather events, safeguarding lives, infrastructure, and valuable land from the devastating impacts of flooding [1,2]. Additionally, river levees play a critical role in enhancing climate resilience by adapting to changing hydrological patterns, safeguarding urban and agricultural areas, and promoting economic stability [3,4].…”