The multi-energy complementary balance model used in the demonstration of the scale of pumped storage in the new power system only considers the high cost of deep peak shaving brought about by the minimum technical output of thermal power for coal-fired unit peak shaving, ignoring the economic issue of coordinated operation between coal-fired and pumped storage units. This paper proposed to use the economic output coefficient of thermal power and the minimum output coefficient of thermal power as discriminant indicators for coordinated operation of thermal power and pumped storage, and incorporate it into the original multi-energy complementary balance analysis model. From an economic perspective, the scale of pumped storage was predicted with the minimum total annual cost as goal. Taking a certain power grid as an example, the process of demonstrating the scale of pumped storage energy was illustrated, which provides reference for similar power grid development planning and early engineering design work.

Aiming at the nonlinearity and non-stationary of vibration signals of hydropower units and the timeliness of prediction, this paper proposed a vibration prediction model of hydropower units based on VMD-CIMFs-TCN. Firstly, the VMD algorithm was used to decompose the vibration signal to obtain the IMFs component with the minimum signal distortion, which realizes the accurate decomposition of the vibration signal. Secondly, by calculating the power spectrum entropy and the permutation entropy of each IMF component, the aggregation of the IMF components was realized to reduce the computational load of the prediction model. Finally, the TCN network was used to realize the accurate prediction of CIMFs, and the final vibration signal prediction results were obtained by adding them. The analysis shows that this method shortens the time required for prediction on the premise of ensuring the prediction accuracy, and meets the timeliness of the prediction model.

Analyzing the spatial and temporal distribution characteristics of flash flood disasters is crucial for flood control and prevention. Taking Guangdong Province as an example, this study first compiled historical data on flash flood disasters in Guangdong Province from 2017 to 2021. Using methods such as standard deviation ellipse and kernel density, the spatial and temporal characteristics were analyzed, and the complex interaction relationships of triggering factors were explored. The results show that there were a total of 79 flash flood disasters, mainly concentrated in May and June, with uneven temporal distribution. The spatial distribution pattern of flash flood disasters exhibited a "dispersed east and west, concentrated north and south" pattern, with the northern cities of Heyuan, Shaoguan, and Meizhou being high-risk areas for flash flood disasters. Short-duration heavy rainfall was the main driving factor for flash flood disasters, with significant influences from topography, vegetation cover, and land use. The findings of this study can provide reference for flash flood disaster prevention and control in Guangdong Province.

In order to solve the problem that the one-dimensional SWMM model is difficult to visually display the submerged depth and range of the study area, taking a residential area in Brighton as an example, the SWMM model coupled with the LISFLOOD-FP two-dimensional hydrodynamic model has a low impact on the residential area. The waterlogging situation before the development and renovation was analyzed and the inundation range and water depth map were made, and three different low-impact development (LID) schemes (single green roof scheme, single permeable pavement scheme, and combination scheme) were designed to transform the residential area. The results show that the inundation range is consistent with the actual waterlogging points, which shows that the two-dimensional coupling model has high reliability, and the three low-impact development schemes can effectively eliminate overflow nodes, reduce runoff peaks, and delay peak occurrence time and water receding time, which is of great significance to improve urban drainage and reconstruction technology.

Considering the wide frequency range, strong nonlinearity, and multimodal characteristics of "double high" power systems, an adaptive identification method for broadband oscillation modes was proposed. Firstly, an adaptive threshold filtering technique was applied to the spectrum of the Blackman-Harris windowed signal to extract the dominant components. Then the three-spectrum line interpolation FFT and the ZoomFFT were used to adaptively analyze the signals after using main-lobe interference criterion of modes with close frequencies. Finally, the proposed method was tested by using 20-mode example signals and a measurement signal of a power system model. The results demonstrate that the method can accurately identify the parameters of complex broadband oscillation modes, adapt to various oscillation scenarios, and meet the signal characteristics of "double high" power systems, thus confirming its applicability and feasibility.

The practice of ecological governance and reforestation was carried out by taking Pianyanzi fluctuation zone as the object, proposed the stone cage anti wall technology, stone cage plate slope protection technology, ecological bag slope protection technology, which provides the necessary soil matrix for plant growth and prevents the soil from being soaked by reservoir water and erosion. On this basis, more than a dozen species of water-resistant plants were screened, and different plant species were configured in different elevation areas. After a long period of inundation in one hydrological year, the overall survival rate of trees and shrubs was 54.9% and 35%, respectively. Among them, Taxodium ascendens Brongn, Ascendens mucronatum, Betula nigra, Myricaria laxiflora, and Salix variegata had better submergence tolerance and higher survival rates, which were 84%, 74.2%, 88.3%, 97%, and 95%. They could withstand long-term overtop submergence, and the effect of reforestation in the water-level zone was obvious.

In order to fully reflect the natural environmental conditions and effects formed and maintained by the river ecosystem, which is the basis of human life, after in-depth analysis of the river ecosystem service function, the calculation method of carbon fixation and other functions was optimized. Based on the functional value method, a scientific and reasonable river ecosystem service value (ESV) evaluation methods covering more comprehensive functions was proposed, and Nanhe River ESV in Liyang City was studied with an example. The total ESV of Nanhe River in 2019 is 1.242 billion yuan, with the value of regulation, support, supply and cultural functions accounting for 76.5%, 12.2%, 11.1% and 0.2% respectively, which can provide reference for natural resource asset accounting and ecological compensation standards.

In order to investigate the influence of the vegetation in beach and river bottom on the water flow characteristics at different time periods, under the condition of changing the vegetation diameter (6-10 mm) only, the numerical simulation was used to study the variation of vertical velocity distribution, contoured velocity, water level and intensity of turbulence along the way at different vegetation diameter. The results show that the vertical velocity distribution shows an "S" distribution in the vegetation zone and a "J" distribution outside the vegetation zone; In general, the larger the diameter is, the lower the overall velocity is, the more obvious the upstream congestion of the water level is, and the larger the water surface slope ratio is; The turbulence intensity is proportional to the vegetation diameter; The turbulence intensity of water flowing through the vegetation is greater than that of the vegetation channel when the vegetation diameter is the same.

Geotechnical engineering generally involves three-dimensional steady seepage problem with free surface. Traditional numerical methods for solving free surface are based on the assumption of continuum, and the pore flow is averaged over the whole area containing solid particles. In fact, water flow can only occur along the pores of porous media. Based on the equivalent principle of head and flow, the equivalent seepage velocity, continuity equation and boundary conditions of the pipe network model were derived by simplifying the pore structure of porous media into a three-dimensional orthogonal pipe network. Based on the local coordinate system, continuous penalty Heaviside function and variational principle, a three-dimensional steady seepage analysis method with free surface was established for equivalent pipe network model. Thus, the three-dimensional seepage problem was simplified to a one-dimensional form, which greatly reduces the difficulty of solving the three-dimensional steady seepage problem with free surface. The effectiveness of the equivalent pipe network model was verified by the three-dimensional free surface seepage analysis of homogeneous right-angle trapezoidal dam. The three-dimensional steady seepage analysis of the left abutment slope of Kajiwa Hydropower Station was carried out. By comparing with the variational inequality method, the equivalent pipe network model can well reflect the seepage field characteristics of the left abutment slope of Kajiwa Hydropower Station, and has strong applicability and high computational efficiency for the seepage problem of 3D complex engineering.

A typical urban channelized (Urban) channel in Liangtan River, Chongqing, was reshaped into six types of channel by a numerical simulation tool named RiverBuilder. And then a two-dimensional hydrodynamic convection-diffusion model was constructed to study the effect of channel morphology reconfiguration on migration and diffusion index, such as water turn-over time (T_TOT), pollutant concentration curve (C_CC), pollutant reaching maximum time (M_MT) and pollutant arriving time (A_AT). The results show that the channel morphology reconfigured by changing the width (W_bf), depth (D_bf), and meandering (M_d) of the Urban channel can inhibit the migration and diffusion of pollutants to a certain extent, but the influencing effect is not as good as that of the composite channel based on the variable D_bf. Meanwhile, the near-natural (Natural) channel has the strongest anti-pollute capacity and inhibiting ability of pollutants diffusion, indicating it is more suitable for the self-purification process of pollutants. It is confirmed that the channel morphology based on disordered and complex changes in W_bf, D_bf, and M_d is closer to the Natural channel, which can provide good eco-hydraulic conditions for the improvement of river water quality.