Study On Impact Of Human Activities For Flood Forecast And Flood Protection Operation

In China flood disaster happens continually and it often results enormous losses. However,water resource absence is one of outstanding problems in our country.Because the exploitation of flood resource can promote human and the nature harmoniously,utilizing hydraulic engineering fully(especially reservoir) is the important measure of lessening flood disaster and solving water resource crisis under the premise that the safety of flood control is insured.This paper combines the flood protection and disaster mitigation research projects of author affiliation.In this paper,firstly the hydrological effects with human activities are studied,and it is included in flood combined forecasting method which improves the precision of flood forecasting.Then the variational characteristic of flood protection ability of reservoir downstream river course is introduced to establish flood protection forecast operation,which result is more useful and rational.Finally the variable fuzzy optimization model is adopted to optimize the flood protection engineering schemes and the dynamic flood control limited water level schemes,which provides decision-making proofs for flood control of some basins and real-time operation of reservoirs.(1) With the increasing impact of human activities on the basin's hydrologic cycle,it is necessary to quantitatively analyze the influence of hydrological forecasting by human activities.Firstly the impact of human activities on Biliuhe reservoir basin and Fengman reservoir basin are analyzed respectively and the result is gained that the impact of human activities on Biliuhe reservoir basin is much smaller than Fengman reservoir basin.Then the change-point of the impact of human activities on basin's hydrologic cycle is gained with the analysis of basin's underlaying surface changes and hydraulic projects running conditions,and it is validated by analysis on rainfall runoff trend.And hydrological effects with human activities are stressed based on data mining method.Then the reservoir storage scales inference model is established based on decision tree with Fengman reservoir basin for example which has remarkable human activities impact and lacks for reservoir operation data.Finally the established inference model is validated by T-S fuzzy inference method and the results of both inference methods are coincident.It is verified that the precision of the established inference model is comparative high,the corrected effect of the flood volume forecasting results using the established model is good comparatively and the model is applied to practically supervise flood forecasting. (2) Bayesian probability forecast method is introduced which takes human activities impact into account.The method calculates reservoirs storage scales and storage process on the basis of the established hydrological effect inference model,and the primary forecasting scheme is modified in real time by the storage process.Bayesian probability forecast method converts the prediction results of the primary forecasting scheme by the posteriori distribution function,and Gibbs sample is processed for high dimensional distribution function by MCMC. Then the eigenvalue and expectation of the distributed function are found by iterative operation,and the expectation is the result of probability forecast.The minimum,maximum and optimum real time emendation function of human activities impact is considered respectively in the sampling process.Finally the precision of the Bayesian probability forecast method is validated by taking the Fengman reservoir basin for instance.The result indicates the method is feasible and practical,and its precision overwhelms the primary forecasting scheme.The flood peak forecasting has a great impact on hydrological effect of human activities,and forecasting of the time flood peak appearing has a lesser impact on hydrological effect of human activities.(3) Taking the downstream river course of Biliuhe reservoir,protected area(Chengzitan Town) for instance,according to the situation of practical flux data absence for downstream river course of the reservoir,the one-dimensional river network model(MIKE11) is introduced to simulate its flood protection ability by controlling variables under various project-situation(such as different rough rate coefficients of riverbed,tide) and it is validated by HydroInfo hydraulic software.The impacts of rough rate coefficients of riverbed and tide for the flood protection ability,are analyzed respectively,and the conclusion is that the rough rate coefficients of riverbed is sensitive for the flood protection ability of all river course and the tide is sensitive for the flood protection ability of the entrance of the sea.Then the one-dimensional river network model(MIKE11) and the two-dimensional river network model(MIKE21) are introduced to calculate and analyze the flood inundation status for the downstream river town of the reservoir,and the flood inundation status are evaluated by zonal flood loss evaluation method which can offer the support data to risk management of reservoir in flood season.Finally the flood protection information system for downstream river course of reservoir is designed on the basis of B/S mode.which can provide decision-making proofs for joint operation system.(4) To some reservoirs with the task of flood control and while near by the entrance of the sea,the flood protection ability of downstream river course shows great uncertainty, which varies with the following factors,bed roughness,tide,sea-wind and so on.However, the actual flood protection forecast operation modes are established by taking it into account as an invariant.If so,while the flood protection ability of downstream river course is lower, maybe we get losses if we undergo flood operation taking the old modes,whereas,we will bear economic loss because of releasing floodwater ahead of schedule.Aimed at those situations,with the background of Biliuhe reservoir,this paper develop a new flood protection forecast operation mode,which based on the classification of the flood protection ability of downstream river course.To further attest its feasibility,the new mode is adopted in operating three floods.The results show that the mode is useful and rational.(5) Taking the Biliuhe reservoir and its downstream fiver course,protected area (Chengzitan Town) for instance,the variable fuzzy optimization model is adopted to optimize the flood protection engineering schemes and the dynamic flood control limited water level schemes.Proceed from the submerging state,society,economy and ecology angles,the submerging ares the deepest submerging depth,economic loss of flood disaster,the schema construction cost,social harmonious degree and ecological environment influence coefficient have been as optimization indices.The optimization results show that the schema "Reinforcing the dangerous banks and dredging some watercourses of lower flood standard and enhancing standard to 18-year flood" is suited for the local actual situation.Based on the analysis of the factors influencing the dynamic flood control limited water level of a reservoir, the evaluation index system on optimizing dynamic limited water level schemes is established. The flood disaster losses of Chengzitan town at the lower of the reservoir,the flood control risk of a reservoir,the mean annual generated energy,the utilization rate of water resource and the reliability of water-supply guaranteed rate after running up the limited water level are calculated.The satisfying schema obtained will provide an important reference and basis for dynamically controlling limited water level during real-time operation of a reservoir.Finally,the conclusions are draw and the problems to be further studied are discussed.