Prevention of River-Mouth Closure Using a Jetty and Recovery of Spawning Ground of Horseshoe Crab
At the mouth of the Maite River flowing into Nakatsu tidal flat which faces the Suonada Sea, a river-mouth jetty using gravel net was extended to block longshore sand transport from the nearby coast into the river mouth. The effect of the jetty appeared within two months after the installation of the jetty, and sand deposition inside the river mouth was mitigated. Sand was deposited immediately west of the jetty, and it was found that such a sand mound was used for horseshoe crab Tachypleus tridentatus as a spawning ground. The recovery of sandy beach west of the jetty was effective for the protection of sand dune as a natural levee.
KeywordsNakatsu tidal flat Maite River river-mouth improvement gravel net horseshoe crab spawning ground
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