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The disasters of encounter of extreme rainstorm and high tide level will aggravate the flood in coastal cities.In order to explore the impact of the encounter of rainstorm and tide on flood control and drainage in coastal cities,based on the annual maximum 1 day rainfall and its corresponding tide level data of Chiwan Station in Shenzhen from 1967 to 2018,the Copula function is used to construct a joint distribution model of annual maximum 1 day rainfall and its corresponding tide level,and the co-occurrence risk,the flood control risk,the condition risk and the combination risk of rain and tide in Shenzhen are calculated and analyzed.The results show that the risk of the encounter of rain and tide in Shenzhen is small,and the co-occurrence and combination risk probability of rainfall whose return period greater than 100 years and tidal level whose return period greater than 200 years are only 0.12% and 0.09%.The probability of the occurrence of rainfall or tide exceeding the standard magnitude is 1.09%,and its return period is less than 100 years.When the rainfall exceeds the standard magnitude,the probability of encountering an over-standard tide level is greater,with a probability of 12.33%.At the same time,with the increase of rainfall,the risk will also increase.Therefore,in the planning and design of flood and tide prevention and drainage in cities,the focus should be on attention and prevention.

With the rapid development of social economy, there is an interactive coupling andcooperative competition between regional water resources system and socio-economic system. TakingGuangdong Province as a case study, this paper studies the coordination degree of the socio-economic and water resources system from 1980 to 2017 in the region by combining the relativedispersion coefficient method and the coupling function method. The following conclusions aredrawn: ① Based on the conception of coupling function, the degree of coupling coordinationbetween the two systems is accurately quantified by calculating the relative distance between thesocio-economic system and the water resource system; ② During the study period, the coordinationdegree of the combined system shows an overall increasing trend. In the early period of 1980—2005, the combined system was at a moderate level of coordination. While in the later period of2005—2017, the coordination between two systems was at a high level.

The river and lake system is the carrier of water circulation and water resources inriver Basin. The pattern of river and lake system interconnection will have a major impact onregional water demand, such as flood control and drainage, water resource utilization andecological environment protection. Taking the Xijiang River and Beijiang River Delta as theresearch object, and taking into full account the information of natural geography, hydrology andhydraulic engineering, this paper analyzes the structure of the river network in delta,establishes the natural nodes and artificial control nodes of the river network, and on such abasis, hierarchically divides the river network in delta according to the water system,embankments, area and creeks., and constructs the regional and hierarchical scheduling structurefor the sluice pump group in the river network area based on the distribution of water resources,water environment, node and important water diversion and drainage channels.

The river basin cascade development has prominent influence on water ecology for breeding of four major Chinese carps, and the determination of ecological operation objectives is an important basic work to carry out the ecological operation. This study determines the main control indexes of reservoir operation by analysing the relationships between larval population of Xijiang Dongta spawning ground and impact indexes like water temperature, flood process and flow velocity. Taking peak flow, initial discharge, flow rising range, daily increasing rate of flow and duration of water level rising of the spawning ground as the control indexes, the target flow process of reservoir ecological operation can be determined. Furthermore, the drifting velocity of fish eggs is used as the test index to control the section flow in the scheduling river reach. The proposed method is applied to the ecological operation of Dongta spawning ground, and the target flow processes of ecological operation under low, medium and high flow levels are obtained.