The stability number of a breakwater can determine the armor unit’s weight, which is an important parameter in the breakwater design process. In this paper, a novel and simple machine learning approach is proposed to evaluate the stability of rubble-mound breakwaters by using Extreme Learning Machine (ELM) models. The data-driven stability assessment models were built based on a small size of training samples with a simple establishment procedure. By comparing them with other approaches, the simulation results showed that the proposed models had good assessment performances. The least user intervention and the good generalization ability could be seen as the advantages of using the stability assessment models.

Sediment is one of the main factors affecting the ecological environment of rivers, and its eco-environmental effect plays an important role in maintaining the balance of water environment and aquatic biodiversity. Sediment in mountain rivers has obvious characteristics such as wide gradation, which has unique impacts on the ecological environment. In addition, the increasingly intense human activities in mountain rivers, such as the construction and operation of large-scale cascade reservoirs, lead to further complicated changes in the ecological and environmental effects of sediment. In this paper, the environmental effects of mountain river sediment in adsorption, desorption and transport and the ecological effects on aquatic microorganisms, animals, plants and the entire food web were systematically reviewed. The problems existing in relevant researches were discussed, and the research prospects were presented, in order to provide guidance for the protection of mountain rivers.

Hydraulic structures have caused many environmental problems in recent years. Structures such as spurdikes are effective in river regulation but also a threat to river ecology. Therefore, in this paper artificial wetland is considered in spur-dike engineering practice for river restoration. In order to study the influence of this ecological project on the discharge of polluted sediment particles, a laboratory experiment was carried out. The flow field and concentration process around the project area was measured under different conditions of discharge, vegetation and sediment concentration input. Results showed that, the reduction of peak concentration was obvious due to velocity variation. The increase of vegetation occupation ratio would lead to the transition of concentration process diagram from 'single-peak' to 'multi-peak' type. And it's very helpful for the enhancement of water quality and the pollutant decomposition. The pollution reduction amounts and the best parameters of this ecological approach were also calculated.