Morphological characteristics of flood refugia of cobble-bed vegetation

Periodic flooding alters riverine vegetation community composition; moderate flood disturbance maintains communities at an early seral stage, whereas severe floods may remove entire communities. After disturbance, plants may recolonize riverbeds from refugia.Here, we investigated the morphological characteristics of refugia where riverine plants survived large floods. At three sites, plant communities growing on cobble-bars were surveyed, and the hydraulic characteristics of each site were analyzed. The populations of an indicator plant, Anaphalis margaritacea sub-species yedoensis (Franch. et Savat.) were assessed after major floods in 2004 and 2009. At each survey, the particle size and bed composition were measured, and the critical shear-stress required to move particles at each site was calculated. A one-dimensional flow and the average and local shear-stress at ten different discharges, including that of the largest flood were calculated. The results demonstrate that the A. margaritacea community is maintained at locations where the local shear-stress at peak discharge in large-floods does not exceed a critical value. These conditions were achieved in locations with particular morphological characteristics, where the river is not constrained by levees and is restricted by a downstream narrow-pass; in this reach river width increases with discharge thus limiting the increase in water depth with increasing discharge and allowing the establishment of refugia where plant species may survive large floods.Flooding and reestablishment from refugia maintain a characteristic riverbed community in equilibrium.     

Better governance for integrated management of the Lake Biwa—Yodo River Basin

The present study discusses the efforts of the Union of Kansai Governments to resolve serious issues in the Lake Biwa—Yodo River Basin in Japan. It identifies many of the issues related to the basin on a ‘no man's land’ mindset of today's governmental framework, which has constrained both the will and the approach to remedy the associated problems. It also highlights better governance that not only encourages individual efforts, but also promotes collaboration and cooperation among the major stakeholders in the area, as important to developing acceptable solutions to relevant issues. The present study also recognizes objective scientific evidence as an effective driver for improving governance, being the basis for making informed decisions and highlighting the use of appropriate indicators to evaluate the conditions characterizing a specific location or the basin as a whole. The present study also describes the Union of Kansai Governments as a behind‐the‐scenes coordinator that gathers knowledge and intelligence on the basin, and works to integrate policies by getting basin stakeholders to gradually improve governance by repeating a cycle of: (a) recognizing the current situation; (b) identifying relevant issues to be addressed; (c) establishing a framework and policy for collaboration and corporation; and (d) taking necessary actions. To this end, the present study discusses the studies and efforts of the Union of Kansai Governments to develop and implement integrated management of this important interlinked lake–river water system in Japan.     

A network of options: Evaluating complex interdependent decisions under uncertainty

The present article provides a novel framework for analyzing option network problems, which is a general class of compound real option problems with an arbitrary combination of reversible and irreversible decisions. The present framework represents the interdependent structure of decisions by using a directed graph. In this framework, the option network problem is formulated as a singular stochastic control problem, whose optimality condition is then obtained as a dynamical system of generalized linear complementarity problems (GLCPs). This enables us to develop a systematic and efficient numerical method for evaluating the option value and the optimal decision policy.