Ridge and runnel topography at Fukiagehama Beach, Southern Kyushu Island, Japan and its implication as habitat for sandy shore organisms

鹿児島県吹上浜で観察された砂浜生物のハビタットとしてのリッジーラネル地形

Ridge and runnel topography at Fukiagehama Beach, Southern Kyushu Island, Japan and its implication as habitat for sandy shore organisms

Creators Suda Yusuke

Creators Nanjo Kusuto

Morphological characteristics of the ridge and runnel topography, an unfamiliar sandy shore microhabitat, was described based on the levelling researches conducted from May 2000 to June 2016 at mesotidal Fukiagehama Beach, southern Kyushu Island, Japan. Three research sites with different morphodynamic states as reflective northern portion (Kaminokawa), intermediate middle and southern portions (Kyoden, Beach Park) were surveyed. Ridge is an intertidal sand bar exposing during low tide and shallow remnant water shoreward is a runnel as defined by King and Williams's original definition. Shapes and positions of the ridges and runnels were varied from north to south with decreasing wave exposure and beach steepness. In well wave-exposed north portion, relatively narrow single runnel and ridge was formed just below steep beachface, whereas in less exposed middle and southern portions two sets of ridge and runnel were observed on lower intertidal sand flats of at most 200 m-wide in Kyoden and 300 m-wide in Beach park. Knowledge from the previous works imply function of the ridge and runnel topography as habitat and feeding place for sandy shore macrofauna and fish. Topographical diversities such as ridge and runnel etc. induced by beach morphodynamics may affect species diversities of sandy shore ecosystems.

[ISSN]0370-9361