Coastal protection in future climate Per Sørensen, Head of coastal research, Coauthors Holger Toxvig Madsen, Søren B. Knudsen, Matthew Earnshaw, Radu Ciocan, Thorsten Piontkowitz, Marianne Skov and Peter F. Klagenberg
Outline Introduction Flood protection and erosion protection Erosion protection, focus Erosion atlas Erosion protection Flood protection Guidelines for climate adaptation Dessimination COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 2
Main threath s Erosion Flooding COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 3
Passive erosion protection COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 4
Active erosion protection, nourishment methods Fællesaftale 2004-08 2.6 mio. m³ pr. år COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 5
Erosion atlas and 10 analyzed sand nourishments COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 6
Beach nourishments COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 7
Fjaltring Beach nourishment 1992
Nourtec 1, beach nourishment 200.000 m 3 9
15 Morphodynamics, the bar system
16 The design parameters
17 The nourished section design parameters
18 The upstream section design parameters
19 The downstream section design parameters
Conclusions After ¾ year the nourishment has been moved probaly migrated downstream A stronger bar system has developed For the whole monitored area: 1 m 3 nourishment sand substitutes 1 m 3 eroded sand COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 20
Julebæk Beach nourishment 2010
Julebæk beach nourishment COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 22
Surveys and nourishments COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 23
Decay of beach nourishment COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 25
Sediment transport pattern Sediment redistributes mainly crosshore A minor downstream sedimentransport COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 26
Blåvand Beach nourishment 2010
Blåvand Location: northern part of the Danish Wadden Sea, Blåvandshuk Skallingen. Sandy beach (60-100 m wide) Dune up to 6 m elevation Exposed to north sea waves Coastal protection in form present in the form of groynes Nourishment type: Beach Quantity: 125.000 m 3 Monitored using bathymetric surveys COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 28
Volume changes COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 29
Krogen Beach nourishment 2012
Krogen, beach nourishment Location: West Coast of Jutland. Exposed sandy beach (67 m) Narrow dune (<40 m) Continuous sandbar Nourishment type: Beach Quantity: 660.000 m 3 Monitored using bathymetric surveys and LiDAR scans over 20 months Exposed to two seasons of severe weather COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 31
Monitoring programme Segment Width [m] Total [m 3 ] Per length [m 3 /m] North 700 116900 167 Middle 1100 378400 344 South 600 165000 275 Total 2400 660300 275 COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 32
Volume changes 790 690 590 1000 m 3 490 390 290 190 90 Measured development Natural erosion Dean -10 04/2012 10/2012 05/2013 11/2013 06/2014 COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 33
Duneface: Change in design parametres advances 30 m due to the nourishment retreats every year after nourishment one can see the tendency of nature to straighten out artificial undulations Duneface position Shoreline: moves outwards due to nourishment retreats in periods with rough weather advances again in mild weather Shoreline position Profile: most notable changes in 2014.01 and 2014.02 Profile position COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 34
Shoreface nourishments COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 35
Fjaltring Shoreface nourishment 1992
37 Nourtec 1, shoreface nourishment
42 Morphodynamics, the bar system
43 The design parameters
44 The nourished section design parameters
45 The upstream section design parameters
46 The downstream section design parameters
Conclusions The volume in the nourishment box increases to 1.5 times the nourished volume and stays at this level Positive effect on the coastline and the dune face inside Accretion upstream on the beach and in the bar zone. The effect could be influenzed by the beach nourishment upstream The volume increases downstream in the beach and bar zone For the 3.5 km section around the shoreface nourishment the volume has increased by 490,000 m 3 from the start to the end of the monitoring period. It means that the shoreface nourishment has more than counteracted the autonomous erosion The outer bar has become continuous downstream. The inner bar has not become continuous but the segments have become longer COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 47
Fjaltring Shoreface nourishment 1997-98
49 Nourtec 2 shoreface noursihment
57 The bar system, 1997-2001
59 The bar index
60 The design parameters
61 The nourished section
62 The upstream section
63 The downstream section
65 The average effect on the profile after 4 years
Nourtec 2/shoreface summary/conclusion The volume in the nourishment box increases to 86 % of the nourishment volume. After 4 years 58 % is still there The bar trough inside becomes deeper and the coastline advances In the boxes upstream the volume decreases except for the box at the bar where there is accretion Downstream the volume decreases on the beach and in the bar trough. On the bar and just outside the bar there is a small volume increase The average number of bars in the measured profiles has been doubled and both bars become more coherent Compared to the autonomous retreat the coastline advances 58 m behind the nourishment. Advance is also seen downstream Outside the +1 m contour the average profile advances with 15-50 m compared to the autonomous retreat 66
Husby Shoreface nourishment 2007
Husby, 3 shoreface nourishments The aim of the study is to analyze the effects of dividing one long massive bar nourishment into three smaller spaced Am harum nourishments unt dolor sum, tectem delestio eos arunt ut volorem Necerio moloratur Di omnim aut prorum Bus dellicae ea cupis quis dignam susci reptatem re plibus sequi il COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 68
Central nourishment COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 69
Nourishment north COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 70
Space North COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 71
Space South COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 72
Summary and conclusion Short bar nourishments ~ 750 m with 400 m 3 /m gathers sand the first 3 years. Short bar nourishments cause lee side erosion. Short bar nourishments advance the dune foot, the coastline and the profile. It is assumed, that short bar nourishments reduce erosion along the entire section the first years, because the strong bars disturb the long shore transport It is recommended that the gap between the bar nourishments is increased to 3000 m at future nourishments COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 73
Sdr. Holmland tange Shoreface nourishment 2012
Sdr Holmsland tange shoreface nourishment COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 75
Volume change in 1000 m3 Northern nourishment 400 300 200 Entier profile 700-1700 Shoreline zone 900-1100 Inner bar zone 1100-1300 Outer bar zone 1300-1700 Nourishment 2011 100 Nourishment 2010 0-100 01-01-2005 01-01-2006 01-01-2007 01-01-2008 31-12-2008 01-01-2010 01-01-2011 01-01-2012 31-12-2012 31-12-2013 01-01-2015-200 -300-400 Date COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 76
Volume changes in 1000 m3 South of the northern nourishment 400 300 200 100 Entire profile 700-1700 Shoreline zone 900-1100 Inner sand bar 1100-1300 Outer sand bar 1300-1700 Nourishment 2011 Nourishment 2010 0-100 1-1 2005 1-1 2006 1-1 2007 1-1 2008 31-12 2008 31-12 2009 31-12 2010 31-12 2011 30-12 2012 30-12 2013 30-12 2014-200 -300-400 date COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 77
Deposit in 1000m3 Southern nourishment 400 300 200 100 Entire profile 700-1700 Shoreline zone 900-1100 Inner sand bar 1100-1300 Outer sand bar 1300-1700 Nourishment 2011 Nourishment 2010 0-100 01-01-2005 01-01-2006 01-01-2007 01-01-2008 31-12-2008 31-12-2009 31-12-2010 31-12-2011 30-12-2012 30-12-2013 30-12-2014-200 -300-400 Date COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 78
Deposition in 1000 m3 South of the southern nourishment 400 300 200 100 Entire profile 700-1700 Shoreline zone 900-1100 Outer sand bar 1300-1700 Inner sand bar 1100-1300 Nourishment 2010 Nourishment 2011 0-100 1-1 2005 1-1 2006 1-1 2007 1-1 2008 31-12 2008 31-12 2009 31-12 2010 31-12 2011 30-12 2012 30-12 2013 30-12 2014-200 -300-400 Date COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 79
Sand bar movement Sand bar movment offshore =positive 0,5 0,4 0,3 0,2 0,1 0 2010,01 2010,02 2011,01 2011,02 2012,01 2013,01 2014,01-0,1-0,2-0,3-0,4-0,5 Survey COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 80
Numbers of sandbars Total number of sand bars 110 105 100 95 90 85 80 75 70 65 60 2010,01 2010,02 2011,01 2011,02 2012,01 2013,01 2014,01 Survey COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 81
Conclusions Coastal retreat is on average reduced after the nourishment. The number of sand bars increases after the nourishment then continues a declining trend again. The outer sand bar moves in towards the coast as the nourishment sand redistributes itself. There remains is a traceable coastline undulation in the southern part of the study area throughout the nourishment period, however this is the only visible pattern that is carried over from the pre nourishment phase. The nourishment to the north caused an increased in volume in the inner bar zone, which met the design aim. The effect last longer than the last survey i.e. longer than 3 years. An increase in shoreline volumes south of the nourishment is also apparent. The nourishment to the south shows a rapid distribution of half of the nourishment volume to south again fulfilling the design aim. The effect of the nourishment is again longer than 3 years. COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 82
Design recommendations for sandnourishment Knowledge on variability of the coast are crucial Nourishment volume = profile erosion Shoreface nourishment when in due time (cheapest) Beach nourishment when not in due time (disaster management) Shoreface nourishment can disturb coastal system Beach nourishment distribution slower than Dean More R&D is needed COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 83
Adapting coastal flood protection in Denmark
Coastal flood protection in a changing climate Denmark has about 1,100 km of dike line; the reliability of the defences is often unknown Function of sea dikes is essential, as they are protecting high values Hydrodynamic forces on sea dikes will change due to climate change This implies: an improvement of reliability assessments of flood defences to avoid dikes breaches a broader understanding of the importance of sea defence maintenance new thinking of flood protection in the coastal zone COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 85
Reliability assessment of sea dikes Understanding of changing hydrodynamic forces due to climate change Time-dependent aspects such as the frequency and the retention period of hydraulic loading conditions on dikes Consideration of other dike failure modes than wave overtopping Consideration of active wave energy disipatation COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 86
Maintenance of sea dikes Erosion of grass cover layers has been investigated in EroGRASS Aggregate erosion and block erosion is dependent on the frequency of wave loading events Erosion develops sooner at weak locations such as dead plants or bare spots At well rooted locations mostly no erosion, however weak spots in the vicinity have negative effect EroGRASS showed high erosion resistance of wellmaintained grass cover layers Conclusion: Performance of a grass cover layer depends on its management COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 87
Adapting coastal flood protection Degree and pattern of land use and activity are important when designing coastal flood protection Hinterland comprising e.g.: settled towns and villages industrial facilities and sites for hazardous substances e.g. chemical plants conservation areas, biotopes or catchment areas for drinking water abstraction high cultural values Vulnerability of the hinterland defines adaptation of coastal flood protection Not only considerations of a defence line, but more than a defence zone COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 88
Urban areas COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 89
The Danish Dike Manual Guidance on the design and reliability assessment of coastal flood defences, including climate adaptation Focus on sea dikes and vertical seawalls Guidance to good practice in design, construction, maintenance and management Target towards engineers and planners who are familiar with coastal processes and coastal engineering Provides information to support decision making COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 90
When to adapt coastal protection to climate change Guidelines Use of planning lines Use of action lines COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 91
Overall conclusions Coastal protection can be adapted to futures climate Requires more sustainable thinking i Denmark Planning and understanding of coastal processen and their variability is crucial. Multifunctional coastal protection proposed. Socioeconomical approach suggested. COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 92
Højbovej 1 7620 Lemvig Tlf: 99 63 63 63 E-mail: kdi@kyst.dk www.kyst.dk COADAPT, WP2 Coastal protection, Dancore seminar december 3rd 2014 SIDE 93