Due to the sensitivity of the environment and immoderate human activities, the coastal zone in China is facing resource conflicts and environmental pressures. Salt marsh vegetation is regarded as an important measure for coastal ecological restoration. Therefore, it is of practical significance to study the influence of salt marsh vegetation on hydro-sediment dynamics. Based on the measured topography and tidal sediment data, a generalized model of salt marsh vegetation is established to study its effects on the dynamics of nearshore water and sediment. The results show that salt marsh vegetation has prominent effect of attenuating flow velocity and promoting sedimentation, and the ability differs depending on vegetation. Salt marsh vegetation can promote the development of tidal channels to shore, causing intensified erosion in the deep trough. The expansion of the vegetation area will allow the tidal channels to extend small branches to shore and connect with the vegetation front.
Salt marshes are widespread in estuarine coastal areas and are one of the most productive natural ecosystems in the world. More importantly, the role of salt marshes in coastal protection is of increasing interest, as salt marshes significantly reduce wave height and stabilize substrates. However, the application of hydrodynamic models for coastal salt marsh management is still uncommon. In this study, TELEMAC is used to set up a hydro-morphodynamic model to simulate the dynamic process in the study area. After that, the influence of hydrodynamic stress on the salt marshes under natural conditions was analysed and the feasibility of applying artificial structures to restore salt marshes was discussed. Finally, the long-term evolution of salt marsh platform is modelled. The results show that salt marsh vegetation is strongly influenced by coastal dynamics. The artificial restoration measures such as submerged dikes have the potential to restore or rehabilitate salt marshes by attenuating the currents on tidal flats. The long-term marsh evolution contains both platform raising and channel incision, which forms the unique landscape of tidal salt marsh. The research results of the study can provide theoretical support for the management and restoration of coastal salt marsh wetlands and contribute to disaster prevention and mitigation in the coastal areas.
Urban forest is an integral part of the complex urban ecosystem, and tree canopy plays a key role in improving urban climatic environment. Urban Tree Canopy (UTC) is strongly linked to urban thermal environment and living quality of residents. In this study, Luoping County, a mountainous county in southwest China, was selected as the study area to uncover the inner connections between tree canopy and thermal environment, and provide relevant scientific references for the construction of livable forest cities in similar areas. Through eCongnition Developer, ENVI and ArcGIS software, the distribution of Land Surface Temperature (LST) and land cover types in the study area was extracted, 63 patches with super-large and extra-large tree canopy coverage selected, to explore the regulatory effect of UTC patches on urban thermal environment based on SPSS software. Results showed that the highest LST in the research area was 37.63 ℃, the lowest 24.73 ℃, and the average 30.83 ℃. Among the land cover types, the area of buildings and impervious surfaces was 1615.71 hm2, accounting for 55.76% of the total study area, which was the largest proportion and with widespread distribution; the area of grassland and water body was 57.48 hm2 and 12.35 hm2, respectively, taking up 1.98% and 0.43%, with a smaller proportion. Mean LST: impervious surface > bare land > grassland > tree canopy > water body. By increasing the area and perimeter of the patch covered by tree canopy, the cooling rate of the patch can be increased while the temperature inside the patch can be reduced. The relationship between the area and cooling rate is closer than that between perimeter and cooling rate. The increase of perimeter has a stronger alleviation effect on the internal temperature of the patch, whereas, the increase of area has a weaker effect in this respect.
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