洛東江 河口 沿岸砂州 地形 = The Barrier Islands Around the Nakdong River

다국어 초록 (Multilingual Abstract)

This study intend to clarify geomorphic characteristics and geomorphic development of alluvial land form relating with natural environment of the Nakdong River mouth. The investigation is concern with landform classification, stratigraphic analysis, and restoration of the past sea level change, and make an analyis of component of sediment materials.
Especially, this paper is focused on the distribution of grain size which deposited on the strface of the barrier islands. The rerults of this study are as follows:
1. The Nakdong delta consist with three different geomorphic units, those are the upper delta, the lower delta and the marginal deltaic basin.
2. The alluvium which consist of the Nakdong delta is about 60m thick. It had deposited after post glacial transgression.
3. The alluvium of the delta area is classified into,
a) upper sand stratum: 2∼6m thick.
b) clay stratum: 17∼27m thick.
c) lower sand stratum: 4∼17m thick.
d) sand and gravel stratum: 3∼16m thick.
e) basal gravel stratum: 2∼6m thick
4. The hight of natural levee is 1∼4m, it consist of silty sand which transported by sliding or saltation.
Back swamp is consist of clay which transported by suspension.
5. Upper delta is composed of interdistributary islands which developed along the river flow and lower delta is composed of beach-ridges on the Myongho island and tidal mud flat and barrier islands.
Generally, barrier islands have developed almost at a right angle to the river flow.
6. Upper delta is influenced by fluvial processes and lower delta is largely influenced by wave, longshore current, and tidal current etc.
7. The most of alluvial materials are supplied by flood usually occurred from June to September.
8. The Sea-level of around the Nakdong River mouth at B.P 4500 years was above 5m and at B.P 3500 years was above 7.5m and at B.P 1700 years was above 6.5m of the present sea-level.
The Nakdong delta have had formed since B.P 1600 Years.
9. 28 families and 97 species of plants are growing on the barrier islands.
Salsola komarovi, Cynodon ciactylon, and Carexpumila had invaded into the barrier islands as the pioneer plants.
Sand dune formation and subsequent fixation accelerated by pioneer species.
In the salt marsh, Carex scabritolia, Zoysia sinica, and Phragmites communities followed the pioneer species and play a role of same kind of the agent.
The vegetation types of the Jangja island and the Baghapdeung were divided broadly into two groups; mixed plant community of sand dune vegetation dominated by Cynodon, Lathyrus Japonica and Oenothera odorata, and salt marsh vegetation dominated by Carex scabrifolia, Phragmites communities and Zoysia sinica.
The vegetation of the Saedeung and the Namusitdeung were limited in the centeral parts because of ecological performance was so early and very poor compared with those of the Janja island and the Baghapdeung.
Barrier islands had developed the Jangia island, the Baghapdeung, the Namusitdeung, the Saedeung orderly.
10. During flood times, most of the Nakdong River sediments are discharged out of the river mouth by suspension and bed load. And then the suspended load discharged into the Korea strait and the bed load deposited near the barrier islands. In no flood time, the coarse materials of the bed load deposited at the barrler islands by wave activities, and the finer ones deposited within the river mouth by flood tides.
11. The analyze of grain size in barrier islands sediments are as follows:
The shapes of histogram for grain size distribution have single peak and are concentrated. It is noteworthy that since the materials hold finer grains, the shape of histogram enlongated tail to the right side.
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Saedeung Baghapdeung Namusitdeung
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Mø 1.5 2.4 2.46
SDø 0.36 0.33 0.4
SK -0.2 0.16 0.06
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The grain size of the barrier islands distributed from 2ø to 4ø and the peak is 3ø. In the distribution curves of cumulative grain size on normal probability paper most deposits constitute with three straight segments which are: lower, middle and upper segments. These three segments were labelled as coarse, medium and fine population.
It is that coarse population reflects rolling and sliding, medium population reflects saltation, and fine population reflects suspension mechanism, respectively.

목차 (Table of Contents)

• Ⅰ. 序 論
• Ⅱ. 硏究地域의 槪觀
• 1. 地 質
• 2. 微地形分類
• 3. 氣 候
• 4. 河川의 特色
• 5. 海水面變動
• 6. 植 生
• Ⅲ. 堆積物 考察
• 1. 堆積物의 起源
• 2. 堆積相과 堆積環境
• 3. 堆積物 粒徑分析
• ① 代表値上의 特色
• ② Histogram上의 特色
• ③ 正規確率紙上 粒徑累加頻度分布의 特色
• ④ 各代表値間의 關係
• Ⅳ. 地形發達
• 1. 地形發達
• 2. 地形變化 및 三角洲, 砂州形成 모델
• Ⅴ. 要約 및 結論