Presentation by Dano Roelvink (Deltares, IHE Delft) at the XBeach X (10th Year Anniversary) Conference, during Delft Software Days - Edition 2017. Wednesday, 1 November 2017, Delft.
2. 2
There was a time before XBeach...
• FIMP study, Long Island, NY
• Study carried out by Moffatt and Nichol and Delft Hydraulics for
NY District USACE
• Effect of breaching on water levels backbarrier modelled using
Delft3D
• Dune erosion and overwash not yet included properly
• Still, study showed reduced flood levels in back bays if actual
breach growth during flood was taken into account
4. 4
Cross-section Old Inlet
during 1938 storm
• Bloody thing would not
overtop!
• Dune had to be lowered
using SBeach :=(
• Missing:
Infragravity waves
6. 6
Motivation
• 2004 Hurricane season hit Florida coast 4 times
• Congress awarded multi-million project MORPHOS3D to
develop new physics-based model system to assess hurricane
impacts
• Scope: wind-surge-waves-nearshore processes-impacts
• Play ‘what-if?’ games around Corps of Engineers projects
Figure 1 Pre- and post hurricane Ivan, Perdido Key, Florida (source: USGS)
7. 7
Framework
• 3-year R&D Project granted through European Research Office
of ERDC to Delft consortium including UNESCO-IHE, Delft
Hydraulics and Delft University of Technology
• Objective:
‘the further development of MORPHOS3D through the inclusion
of modeling approaches recently developed by a consortium of
Delft institutes.’
8. 8
• no proprietary code used
• all developments public domain (GPL)
• easy to understand and transfer
• focus on physical processes rather than informatics, I/O
• emphasis on robustness
• focus on shallow water, swash, overwashing, breaching
• Swash and overwashing dominated by LF motions
Requirements development
environment
XBeach
9. 9
XBeach - approach
• open source code available for free on internet (xbeach.org)
• easy to use
• Short-wave averaged but long-wave resolving modeling of
waves, flow and morphology change in time-domain
• Swash and overwash motions
• Dune erosion, overwashing, breaching and full inundation
• Domain from outside surfzone to backbarrier
• Driven by boundary conditions from surge and spectral wave
models
13. 13
Institute For Water Education
UNESCO-IHE
WL | delft hydraulics
HF, LF and total Hrms HF, LF and total Urms
Measured (red) vs computed
mean transport
Initial, final measured and
computed profile
17. 17
Code development and documentation styles
if (xmpi_isright .and. s%ny>0) then
! Fy(:,ny+1)=Fy(:,ny) ! only a dummy point in non mpi
s%Fx(:,s%ny+1)=s%Fx(:,s%ny) ! only a dummy point in non mpi
! ! where (Fy(:,ny+1)<0.d0) Fy(:,ny+1)=0.d0;
!Jaap + Bas: Don't do this before calling Dano :-)
endif
! cjaap: replaced par%hmin by par%eps
!s%hh = max(s%hh,par%eps)
! Robert: how is this mass conservative?
!where(wete2d==1)
! s%hh =max(s%hh,par%hmin)
! note: replace with new limiter?
!endwhere
if (xmpi_isright .and. s%ny>0) then
! Fy(:,ny+1)=Fy(:,ny) ! only a dummy point in non mpi
s%Fx(:,s%ny+1)=s%Fx(:,s%ny) ! only a dummy point in non mpi
! ! where (Fy(:,ny+1)<0.d0) Fy(:,ny+1)=0.d0;
!Jaap + Bas: Don't do this before calling Dano :-)
endif
! cjaap: replaced par%hmin by par%eps
!s%hh = max(s%hh,par%eps)
! Robert: how is this mass conservative?
!where(wete2d==1)
! s%hh =max(s%hh,par%hmin)
! note: replace with new limiter?
!endwhere
23. 23
Similar erosion and
deposition patterns:
• erosion of dune
face
• deposition on
island
Overwash case: Santa Rosa Island
McCall et al,
CE 2010
24. 24
18th month meeting – 23-27th Nov. 2009, Montpellier
MICORE.EU Field measurement sites in Europe
25. 25
Some MICORE results..
• Wide application, away
from developers, of
XBeach
• Good results for a
number of cases
• Acceptable but not very
accurate results for
intermediate beaches
• Gravel beaches require
more sophisticated
approach
Oostende
Praia de Faro
27. 27
Meanwhile on the other side of the world...
13/01/2011 06:15
Hi,
my name is Jens Kruger, Oceanographer at the Secretariat of
the Pacific Communities (SPC), a regional organisation
serving 26 members in the Pacific region. I am currently
writing a research proposal in partnership with Susanne
Pohler, Lecturer in Marine Geology, University of the South
Pacific (USP), the primary tertiary institute for the Pacific
region; and also in association with Paul Kench, Associate
Professor, University of Auckland, NZ (hello again Paul!).
I am writing to invite you to go enter into a partnership with
us on this research proposal tentatively entitled “Changing
Waves and Coasts in the Pacific (WACOP Project)”, with
the objective to provide information on wave climate
variability and trends and consequent coastal vulnerability
for informed adaptation and energy security......
28. 28
Extreme sea levels at Pacific islands
Commonly cited cause:
tropical cyclones =
storm surge (+ tides)
Cyclone Mena - Rarotonga
Hydrodynamic modelling of wind- and pressure driven
storm surge from “synthetic” cyclones (Fiji)
1 in 100 year storm tide
McInnes, at al. (in review)
Global and Planetary
Change
29. 29
IG wave modelling at Ningaloo
In collaboration with Univ. of
Western Australia, Ryan Lowe
Recent field studies show
dominance of infragravity wave
motions
Research questions
What is the skill of XBeach on a coral
reef?
What effect do infragravity waves
have on particle motions and
currents?
30. 30
Instrument array and wave data (R. Lowe,
UWA)
swell energy decays rapidly, IG motions pick up and dominate
spectrum
31. 31
Model (red)-data (black) comparison
(swell)
rapid swell wave
height decay from
C1 to C3
swell variance on
reef well
predicted.
very high bed
friction dominates
32. 32
Model (red)-data (black) comparison (IG)
IG wave height
response well
predicted across the
reef.
IG wave heights are
larger than swell
wave heights.
34. 34
Ongoing work (PhD Johan Reyns)
• Implementation/validation of XBeach (and Delft3D) sediment
transport and morphology algorithms in Delft3D-FM
• Application to complex coral reef environments
• Perspective: most of XBeach funtionality available in flexible-
mesh environment soon
39. 39
Runup and overtopping for steep profiles
• Use of nonhydrostatic XBeach validated against lots of lab data
Runup on complex profile Dike overtopping CLASH
40. 40
Bigger, better, faster....
• Improvement of MPI parallellization
• Two instead of one row/column overlap between domains ->
fewer variables to pass
• Much more accurate
• Reasonable scaling up to 128 processors
• Nonhydrostatic model and stationary wave model now also
work with MPI
• Pretty much the default option thanks to Willem Vermin
42. 42
Multi-dir vs single-dir wave propagation
• Multi-dir (standard XBeach):
• Wave refraction resolved as propagation through theta-space
• Leads to excessive reduction of groupiness for directionally spread waves
• Single-dir:
• Solves energy balance along mean wave directions
y w f vx
c A D D DA c A c A
t x y
cos sing g w f vc A c A D D DA
t x y
44. 44
Single vs. multi-direction approach
+
Roughly 3 times faster
Wave group patterns less smoothed out
Likely higher IG waves in 2DH
May solve problems reported in Stockdon et al 2014
-
Will only work where stationary approach works, viz. not too
curved grids
47. 47
Going to longer timescales – coupling Delft3D
and XBeach
• Example development of Wilderness Breach after Hurricane
Sandy
• PhD Maarten van Ormondt (Deltares/IHE)
• Competing effects of tides wind, waves, infragravity waves
• Delft3D for moderate conditions, XBeach for storms
49. 49
Building better berms
• Problem: XBeach does not like steep beaches as are often
present with relatively coarse sediments
• Example: Praia de Faro,
standard settings
50. 50
Approaches
• Improve non-hydrostatic, wave-resolving modeling of
processes in swash zone
• Breaker turbulence
• Sheet flow behaviour
• In/exfiltration
• Vertical velocities... Much fundamental work to do
• See presentation Chris Daley
• Nudge XBeach- surfbeat to given slope in swash zone
• Swash zone narrowly defined as H/h>1
• Add transport term depending on difference between actual and target
slope
• Works like a charm