Lectures 11&12

Coastal hazard management options: a coastal manager should go through these five options in this order

 

Coastal hazard management options: a coastal manager should go through these five options in this order 

1. Do nothing. Allow the infrastructure to bear the full brunt of the hazard

2. Avoid: prevent any development in the zone the hazard affects by creating an excursion zone

3. Accomodate: change the building code, change insurance premiums, change the land use to something less vulnerable

4. retreat

5. Protect with a seawall. This is a band-aid solution, nature always wins in the long run. That’s why this is the last option

 

what is the development-defence-disaster cycle?
The development-defence disaster cycle starts with a natural hazard event that raises concern about vulnerability. To reduce vulnerability, mitigation efforts are put in place. This makes people feel safe, they develop more until the risk is back to where it was, and then another natural hazard event starts the cycle again

Areas of law that coastal managers must take into account (7 areas):

 

7 areas of law that coastal maganers must take into account

1. 1991 resource managent act, or RMA. This includes the New Zealand coastal policy statement, or NZCPS

2. international agreements worked into NZ law

3. Fishery/aquaculture law

4. laws covering mining/petroluem

5 conservation law

6. laws governing transport, waste disposal and pollution

7. Maori Treaties 

2 important parts of the RMA

two important parts of the RMA 

1. The RMA requires sustainable management that works to mitigate environmental destruction resulting from activities on the coast

2. the RMA vies the natural character of the coastal environment as a matter of national importance 

what is the only mandate to come out of the RMA?
the only mandate to come out of the RMA is NZCPS
the NZCPS requires the ministry of conservation to do what?
the NZCPS requires the ministry of conservation to write regional coastal plans
what is the biggest change in the 2010 NZCPS?
the biggest change in the 2010 NZCPS is that local governments must also include how climate change will affect thier beaches and how they are managing resources sustainably
Giving both the regional council and the city/district a role in deciding how to manage coasts acheives what goal?
the goal of the regional council is to protect the coast, and protect people from coastal hazards. The goal of the city/district is to provide services. Letting them both have a say promotes a healthy balance
the the coast is split into what three management zones?

the coast is split into three management zones

1. from the hinterlands to the shore line, the dry land part of the beach, is under the management of the district councils. examples: CCC, MoC

2. from the shoreline to 22.2 km out is the Coastal Marine area, or CMA. This is under the management of regional councils working under the NZCPS

3. from 22.2 to 370+ km is the EEZ, which NZ has a right to exploit and manage under a UN law

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each of those zones is managed by a different body

The zone from 370-22.22 km is NZ’s EEZ. Under UN law, NZ gets to exploit and manage it’s EEZ however it wants

The zone from 22.22km out to the shore is the CMA, coastal marine area. The NZCPS gives regional councils management responsibilities.

The dry land part is managed by district councils 

NZ’s monitoring network looks at these 5 things

 

NZ’s monitoring network looks at

1. waves

2. sea level change

3. Surface sea temperature

4. dissoved CO2

5. water quality 

what are 5 things you need a permit to do on NZ beaches?

5 things you need a permit to do on NZ beaches

1. mine sand

2. build structures like seawalls or artifical reefs

3. make a marine farm

4. introduce exotic plants

5. dump anything 

why does NZ have a weaker coast monitoring program than countries like Korea or Japan?
NZ has a weaker coast monitoring program than countries like Korea or Japan b/c it can’t afford a better one. NZ has a lower GDP per meter of coast than those nations
Westport case study
the Westport case study shows us how rising sea levels will increase the recurrence intervals for floods
where does MGMT option 1: do nothing make the most sense?
MGMT option 1: makes more sense the less development there is
what is one downside of MGMT option 1: do nothing that is human related?
the downside of MGMT option 1: do nothing that is human related is that people will create homemade physical barriers to erosion
coastal excursion zones are what MGMT option?
Coastal excursion zones are MGMT option 2: avoid
what are pros and cons of MGMT option 2?

MGMT option 2 is avoid. Pros: cheap, simple, foolproof. 

Cons: impossible on developed land (that would be retreat). If on eroding land, it’s not fixing the problem, just buying more time 

who opposes coastal excursion zones?
developers who could make money developing the coast
what did Gibbs do?
gibbs make an equation to determine the size of the coastal excursion zone
four parts of Gibbs equation

the Gibbs equation has four parts. 

1. erosion from max storm event

2. long-term propgredation/erosion

3. erosion from SL rise

4. factor of safety for error  

3 problems with Gibbs equation

 

3 problems with the Gibbs equation for predicting coastal setback (long-term erosion) 

1. requires detail record of past beach profile

2. effect of max storm event hard to predict

3. who sets the time span?

3 ways to achieve coastal MGMT option 3 

 

coastal MGMT option 3 is accomodate. there are three ways to go about this

1. minimize the affect of erosion and sea advance on exisitng structures and people. building on stilts, better drainage, better flood warnings

2. better land use plannings

3. acceptance. insurance premiums go up, property values may go down  

three cons of coastal MGMT option 4

two cons of coastal management option 4

1. expensive. use christchurch as an example 

2. not feasible if there is no where to go 

3. much infrastructure can’t be moved

the red zone in CC is an example of what challenge?
the red zone in CC is an example of how politically difficult and expensive it is to move people out of a developed area, which is MGMT option 4: retreat
what is the coastal MGMT option that doesn’t allow coastal processes to run thier course?
the only coastal MGMT option that doesn’t allow coastal processes to run thier due course is option 5: protect.
break down the hard and soft engineering we went over in this class

hard engineering: structures in the water or on the beach or both

soft enginnering: beach nourishment, artificial dunes 

dissapative vs reflective protective beach structures

the dissapative beach structure is revetments

the reflective beach structure is seawalls/embankments 

T-cells/tetrapods
T-cells/tetrapods are man-made blocks that are piled as protective structures. They lock together so storms can’t send them flying at structures
where are embankments preferred?
embankments are preferred near low energy coasts, or next to estuaries prone to flooding. They get destroyed on high energy coasts
what do revetments look like?
revetments look like big piles of rocks
3 kinds of shore parallel protective structures

3 kinds of shore parallel protective structures 

1. seawall

2. revetments

3. embankments 

what process makes seawalls extra expensive to maintain?
the process that makes seawalls extra expensive to maintain is scour at base of seawall
what happens when a seawall extends too far seaward?
when a seawall extends to far seaward it acts as a groyne to trap sediment

3 problems with seawalls 

 

3 problems with seawalls

1. expensive, especially because of scour at base

2. trap water behind seawall, forcing you to pump it out

3. if they poke too far out, they act as groynes and trap sediment 

what is the difference between a breakwater and an artifical reef?
the difference between a breakwater and an artifical reef is artifical reefs are underwater
comparison of price betwee offshore and onshore structures
comparison of price between onshore and offshore structures: offshore structures are generally 3-5x more expensive
functional difference betwen breakwaters and groynes
breakwaters tend to be better and wave sheltering and do less sediment trapping than groynes
any one artifical reef can do one of these two things
any one artifical reef can either lessen erosion or provide a surf break, but not both
this form of coastal MGMT option 5 treats the symptoms of coastal erosion, not the cause
soft engineering is a form of coastal MGMT option 5: protection that treats the symptom of coastal erosion people don’t like, which is beach loss. it doesn’t treat the cause, which is deficeincy in the sediment budget, SL rise
where does beach nourishment make the most sense?
beach nourishment makes the most sense on beaches with high recreational, and thus high economic, value.
when you are choosing sediment to nourish a beach with, what sediment should you choose?
when choosing sediment to nourish a beach with, choose sediment that is coarser, or the same grain size as the sediment on the beach
what is the best way to nourish a beach that will stay nourished for a longer time?
nourishing longer section of beaches means the change stays around for longer
how does one create artifical dunes?
aritifical dunes are made by trapping sand with fences and vegetation
what protection measure is often used with beach nourishment?
artifical dunes are often enacted alongside beach nourishment