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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. One-Line model. Bathymetric change: 2-D. Constant shape: (Dean Profile) . Shoreline change: 1-D (One-Line). One-Line model.

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shoreline model genesis

Shoreline model - GENESIS

Chang HsienKuo

國立交通大學土木工程學系

中華民國102年5月16日

slide2

One-Line model

Bathymetric change:

2-D

Constant shape: (Dean Profile)

Shoreline change:

1-D (One-Line)

slide3

One-Line model

Hanson and Kraus (1989) – Generalized model for simulating shoreline change, GENESIS

Variation of longshore sediment transport

Constant beach profile

slide4

One-Line model

Hanson and Kraus (1989) – Generalized model for simulating shoreline change, GENESIS

D=Db (tidal variation)+Dc (closure depth)=total depth

Q(x) : longshore sediment transport

q : sand source or sink

slide5

GENESIS model

longshore sediment transport

SPM (1984), W:Numerical factor

Ozasa and Bramton, 1980: longshore gradient in wave height

~0.5 >>

breaking waves predicted

slide6

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

slide7

GENESIS model

Example: I-Lan shoreline

slide8

GENESIS model

Specified parameters

Model Calibration

slide9

GENESIS model

Model verification and prediction

slide11

Discussion on GENESIS model

JCR, 1997

Offshore waves: regular wave or observed/calculated waves , H(t), T(t), θ(t)

Engineering Structures and activities

Ex: Beach profile;

Gated boundary of structures

: tip of the structure

slide12

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
slide13

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.
slide14

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.

slide15

Modification on GENESIS model

This paper reviews the 25-plus year history of significant developments of the GENESIS shoreline response model

slide16

Modification on GENESIS model

1. Jetties and groins (sand bypassing and sand transmission)

slide17

Modification on GENESIS model

2. Detached breakwaters and Wave transmission (Kt)

slide18

Modification on GENESIS model

3. Cross-shore variation

Shields Numbers

: Nondimenional falling velocity

slide19

Modification on GENESIS model

4. Sediment transport by tidal (longshore)currents

Bayram et al. (2006)

slide20

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.

slide21

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

slide22

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.

slide23

Recent study - I

Four cross-shore profile models

Ω : non-dimensional falling velocity (H/wT)

slide26

Recent study - I

Impact of temporal sampling (dt:day) < 30days

slide27

Recent study - I

Calibration length vs. model hindcast for seasonally-dominated field

slide28

Recent study - I

  • The design of coastal monitoring program must consider both the type of beach and the resources available.