IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Hydro-environment : 1 a numerical assessment for the effect of filling a sea caldron on seaweed expansion and habitat en...
1 a numerical assessment for the effect of filling a sea caldron on seaweed expansion and habitat environment for aquatic species
An assessment for the effect of a fishing ground newly constructed by filling a sea caldron, whose bottom is generally
formed by muddy sediment and thus which often has low productivity of fisheries, on seaweed (Sargassum horneri)
expansion and habitats for sea grass (Zostera marina) and Cephalochordate (Branchiostoma belcheri) around the new
fishing ground is conducted by using numerical hydrodynamic model and Habitat Evaluation Procedure (HEP). At first,
tidal current in the target area of Seto Inland Sea, Japan, is reproduced by using a multi-level density flow model and then
the current after filling the sea caldron is estimated. From these results, change of the flow field between before and after
filling it becomes clear and consequently distribution of resuspended particle sizes on the sea bottom is estimated based
on the threshold of sediment movement. After filling, maximum tidal current become 10 to 30 cm/s faster than before and
the resuspended particle size is estimated 0.2 to 0.4 mm at the top of the filled area. Next, for estimation of the seaweed
expansion, germlings released from the observed natural Sargassum bed are tracked based on the resultant tidal current
by the use of an Euler-Lagrangian transport model and settling area of them is estimated. The result shows that the
germlings can reach a part of the filled area. Thus if adhesive substrates are properly arranged at the reached area, the
self-formation of the Sargassum bed would be expected. Lastly, Habitat Suitability Index (HSI) is developed for the
evaluation of habitat environment for Zostera marina and Branchiostoma belcheri. Based on earlier studies and our field
observation, velocity on the sea bed and the Shields number are used for Suitability Index (SI) of Zostera marina; median
particle diameter of the sea bed and mud content are used for SI of Branchiostoma belcheri. These results show that HSIs
at one of three observation stations for Zostera marina and one of two for Branchiostoma belcheri slightly rise and those at
other stations slightly degrade. Through the procedure mentioned above, useful information about change of
hydrodynamic condition, seaweed expansion and habitat environment would be given for designing stage of this kind of
File Size : 1,182,787 bytes
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Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Hydro-environment
Date Published : 13/08/2015
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