台湾沿岸短周期水位讯号之现象分析.pptx

,按一下以編輯母片標題樣式,按一下以編輯母片文字樣式,第二層,第三層,第四層,第五層,研究生 李明憲,#,Shoreline model-GENESIS,Chang Hsien Kuo,國立交通大學土木工程學系,中華民國,102,年,5,月,16,日,2,One-Line model,Shoreline change:,1-D(One-Line),Constant shape:(Dean Profile),Bathymetric change:,2-D,3,One-Line model,Hanson and Kraus(1989)Generalized model for simulating shoreline change,GENESIS,Variation of longshore sediment transport,Constant beach profile,4,One-Line model,Hanson and Kraus(1989)Generalized model for simulating shoreline change,GENESIS,Q(x):longshore sediment transport,q :sand source or sink,D=Db(tidal variation)+Dc(closure depth)=total depth,5,GENESIS model,longshore sediment,transport,SPM(1984),W:Numerical factor,Ozasa and Bramton,1980:longshore gradient in wave height,0.5,breaking waves predicted,6,GENESIS model,Flow chart,Positions of some shorelines of different years,Setting parameters required,Model Calibration for K1 and K2,Prediction of futhure shoreline change,7,GENESIS model,Example:I-Lan shoreline,8,GENESIS model,Specified,parameters,Model Calibration,9,GENESIS model,Model verification and prediction,10,Scales of modeling approach and users of GENESIS,More than 1000,11,Discussion on GENESIS model,JCR,1997,Offshore waves:regular wave or observed/calculated waves,H(t),T(t),(t,),Engineering Structures and activities,Ex:Beach profile;,Gated boundary of structures,:tip of the structure,12,Discussion on GENESIS model,Limitations:,Inadequacy of data:waves,Closure depth,Permeability factor,transmission factors for detached breakwaters,Boundary,conditions:later BC or end BC,Rigorous calibration and verifications:numbers of shorelines,13,Discussion on GENESIS model,Restrictions,Predictive reliability,Not applicable to simulating randomly fluctuating beach(e.g.Strom-induced cross-shore sediment),Experience(trained individuals):complexity of beach processes.,Potential,errors also are involved in the hindcast of incident,waves,Tools,that can be misused and incorrect results are,misinterpreted,.,14,Discussion on GENESIS model,Advices for users,It should be kept in mind that the assumptions are idealizations of complex processes and therefore have limitations,In light of profound variability of coastal processes,it is clear that a single answer obtained with a deterministic simulation model must be viewed as a represnetative result that has smoothed over a large number of unknown and highly variable conditions.,15,Modification on GENESIS model,This paper reviews the 25-plus year history of significant developments of the GENESIS shoreline response model,16,Modification on GENESIS model,1.Jetties and groins(sand bypassing and sand transmission),17,Modification on GENESIS model,2.Detached breakwaters and Wave transmission(Kt),Modification on GENESIS model,3.Cross-shore variation,Shields Numbers,:Nondimenional falling velocity,19,Modification on GENESIS model,4.Sediment transport by tidal(longshore)currents,Bayram et al.(2006),20,Modification on GENESIS model,5.Regional depth contour,an open coast without structure or sources or sinks of,sediment,will evolve to a straight line if a standard shoreline response model is run a sufficiently long time.This limitation can be remedied by specifying a fixed representative contour which is appended to the feed-back contour associated with local changes in the shoreline.,21,Modification on GENESIS model,6.Interaction between beach berm and dune,Davidson-Arnott et al.(2005):sand transport to the dune is related to the width of the berm up to some distance over which equlibrium conditions have developed between the wind and the sand surface.,Larson(2004):The erosion rate due to dune impacted by waves run-up,22,Recent study-I,The ability to robustly predict future shoreline position under the influence of changing waves and sea-level rise is a key challenge to scientists and engineers alike.This contribution outlines from 1 to 10 years at wo distinct beach types:a storm-dominant site and the second exhibiting a large seasonal variability.,23,Recent study-I,Four cross-shore profile models,:non-dimensional falling velocity(H/wT),24,Recent study-I,25,Recent study-I,26,Recent study-I,Impact of temporal sampling(dt:day)30days,27,Recent study-I,Calibration length vs.model hindcast for seasonally-dominated field,28,Recent study-I,The design of coastal monitoring program must consider both the type of beach and the resources available.,