Study on the Horizontal Distribution Law of Flood Water and Sediment Factors under the Effect of Vegetation on a Curved Beach

The sediment-laden floodplain flood is affected by beach vegetation and the shape of curved compound channels. The laws of water and sediment exchange and deposition distribution in beach troughs are very complex and play a significant role in the formation and development of secondary suspended rivers, the adjustment of beach horizontal gradients, and even the evolution of flood control situations. This study used a combination of experimental simulations and theoretical research to carry out a generalized model test of floodplain flood evolution, analyzing the transverse distribution characteristics of sediment-laden flow and sediment factors in a curved compound channel under the conditions of beach vegetation, proposing a theoretical model of transverse distribution of velocity and sediment concentration that is based on the momentum equation considering the inertial force of the lateral secondary flow and river curvature. The results showed the following: (1) The model test results for floodplain flood in the compound channel with curved vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharge along the embankment, as the beach siltation was mainly concentrated in the beach lip; (2) The arrangement of full vegetation on the beach had a uniform effect on the velocity distribution of the beach, which can reduce the phenomenon of excessive velocity at the foot of the beach and increase the velocity effect in the main channel; and (3) Through five numerical examples, the lateral velocity distribution model of a curved compound channel with beach vegetation was tested and, in general, the analysis model was consistent with the experimental results. The research results will provide a theoretical basis for river management and have great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology.

Influence of Floodplain Flooding on Channel Siltation Adjustment under the Effect of Vegetation on a Meandering Riverine Beach

Flooding in a sediment-laden floodplain is affected by riverine beach vegetation and the shape of a meandering compound channel. The laws of water and sediment exchange and the deposition distribution in beach troughs are very complex. These factors play a significant role in the formation and development of secondary suspended rivers, in the adjustment of the beach horizontal gradient, and even in the evolution of the flood control situation. In this study, we used a combination of experimental simulation and theoretical research to carry out a generalized model test of floodplain flooding evolution, analyzed the lateral distribution characteristics of sediment-laden flow and sediment factors in a meandering compound channel under the conditions of beach vegetation, and revealed the pros and cons of beach vegetation on the adjustment of the beach and channel siltation. The model test results of the flooding in the floodplain in the compound channel with meandering vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharges along the embankment. As the riverine beach siltation was mainly concentrated at the riverine beach lip, the vegetation on the riverine beach had a significant effect on slowing down the flow velocity. Whether it was a row or full vegetation on both sides of the bank, this played an important role in the stability of the main channel. When there was no vegetation on the riverine beach, the main channel was easy to move. The arrangement of full vegetation on the riverine beach had a uniform effect on the velocity distribution of the riverine beach, which reduced the phenomenon of excessive velocity at the foot of the riverine beach and increased the velocity effect in the main channel. These results will provide a theoretical basis for the utilization of riverine beach areas and river management in the lower Yellow River and have a great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology.

Eksplorasi Vegetasi Kawasan Hutan Pantai Sebagai Atraksi Edu-Wisata Di Pantai Gatra Dusun Sendang Biru Desa Sitihatjo Kecamatan Sumbermanjing Wetan Kabupaten Malang

Gatra Beach in Malang Regency has the concept of ecotourism, but the reality is this beach for camping that is at risk of damaging vegetation in Gatra beach. The purpose of this study are to find out the structure and composition of the Gatrah beach vegetation, knowing the perception of tourists on the vegetation of Gatra beach and knowing the potential of Gatra beach vegetation as a tourist attraction. The method used is the belt-transect method with four stations. Analyses are used i.e., RFC analysis and the SWOT analysis. Analysis of the results obtained by the two vegetation formations that make up the beach Gatra i.e. formation Barringtonia and the formation of lowland forests. Formation Barringtonia found 10 species with index value important highest are Barringtonia asiatica (65,9) and Samanea saman (57,6) Formation the lowland forest found 11 species with index value important highes Musa acuminate (80,2) and Samanea saman (59,5). Tourist perceptions of species of interest in the Barringtonia formation is Samanea saman (0,29), while species of interest in lowland forest formation is Musa acuminata (0,11). So that the beach of Gatra has the potential as an edu-tourism attraction area. Keywords: analysis of vegetation, RFC, tourist attractions, ecotourism, Barringtonia ABSTRAK Pantai Gatra di kabupaten Malang memiliki konsep ekowisata, namun kenyataan di lapangan pantai Gatra menjadi tempat berkemah yang beresiko merusak vegetasi pantai Gatra. Tujuan penelitian ini adalah untuk mengetahui struktur dan komposisi vegetasi pantai Gatra, mengetahui persepsi wisatawan terhadap vegetasi pantai Gatra dan mengetahui potensi vegetasi pantai Gatra sebagai atraksi wisata. Metode yang digunakan yakni metode belt-transek dengan empat stasiun. Analisis yang digunakan melalui analisis RFC dan analisis SWOT. Hasil penelitian menunjukkan terdapat dua formasi yang menyusun pantai Gatra yakni formasi Barringtonia dan formasi hutan dataran rendah. Formasi Barringtonia dengan 10 spesies, indeks nilai penting tertinggi yakni Barringtonia asiatica (65,9) dan Samanea saman (57,6). Formasi hutan dataran rendah dengan 11 spesies, indeks nilai penting tertinggi spesies Musa acuminata (80,2) dan Samanea saman (59,5). Persepsi wisatawan terhadap spesiesdiminati pada formasi Barringtonia adalah Samanea saman (0,29), sedangkan pada formasi hutan dataran rendah yakni spesies Musa acuminata (0,11). Sehingga pantai Gatra berpotensi sebagai kawasan atraksi edu-wisata. Kata kunci: analisis vegetasi, RFC, atraksi wisata, ekowisata, Barringtonia

PLANTING OF RHIZOPORA TYPES IN MANGROVE FORESTS PERCUT SEI TUAN NORTH SUMATERA

Mangrove forest is a tropical beach vegetation community dominated by several tree species that can grow and develop in tidal and muddy beaches. Some mangrove areas recently have been damaged due to illegal activities carried out by various parties, one of which is the East Coast of Sumatra in the Sub District Percut Sei Tuan, Deli Serdang District, Province of North Sumatra. The purpose of the activities is to focus on replanting mangrove lands that have been damaged by local species. The growned in Tanjung Rejo Village Percut Sei Tuan buds are like Rhizopora stylosa, Rhizopora apiculata and Avicennia marina type. Percentage of growing plants were R. stylosa (92.37%), R. apiculata (90%), mixed propagules of R. stylosa and R. apiculata (90%) and A. marina (56%) respectively. Overall the rehabilitation of mangrove forest is categorized as successful, but only one species of the smallest growing with percentage is A. marina (56%) this is because the location of planting is adjacent to the sea where the plants can not stand the tidal currents.