Orewa readies itself in case of Tsunami
But Seawall will cause opposite to desired results
While Orewa gets itself Tsunami ready in the event that one does ever occur its quest to build a sea wall to stop erosion they will find will have the exact opposite effects they were looking for.
From Auckland Council:
Orewa follows the Tsunami signs and blue lines
Auckland Council will be installing tsunami signs in Orewa next week as part of a community-led initiative to increase the coastal town’s tsunami preparedness.
Six information signs will be erected at the facilities on the Arundel Reserve and Western Reserve, Orewa Reserve, Orewa library, community centre and Orewa Top 10 Holiday Park.
Evacuation signs will be installed to indicate major evacuation routes, and blue lines will also be drawn on the ground to mark the ‘safe zones’ for a tsunami practice walk taking place this month (25 May). It will involve local schools, residents and businesses identifying and walking the evacuation route nearest them.
Although the likelihood is low the consequences of a tsunami could be devastating says Auckland Council’s Head of Emergency Management and Operations, Aaron Davis.
“Low lying areas like Orewa are particularly vulnerable to tsunamis so it’s important to be as prepared as possible. These signs will facilitate an evacuation and direct people to higher ground in the event of a tsunami,” says Mr Davis.
Auckland Council’s CDEM team has partnered with Orewa Rotary to effectively engage residents and businesses, says chair of the Civil Defence and Emergency Management (CDEM) Committee, Councillor Sharon Stewart.
“The groundswell of community support for this initiative in Orewa has made it the perfect pilot area for the new signage and mass tsunami walk,” says Councillor Stewart.
“Disaster preparedness is a long-term community need and a key priority for Rotary,” President Elect of Orewa Rotary, Billy Beggs says.
“Rotary has set up a special foundation called CHIP-In to work with communities on this issue. We’re delighted to be working with the Auckland Council CDEM team on the tsunami walk which is the start of our disaster preparedness work in the Orewa community,” he says.
For more information on tsunami preparedness or how to join in the tsunami walk please visit aucklandcivildefence.org.nz
- Since 1840, 16 tsunamis have been recorded on Auckland coasts with wave heights up to 2.9 metres.
- Most tsunamis are caused by earthquakes along tectonic fault lines.
- If you feel a strong or long earthquake, see the tide suddenly go in or out, or you hear a strange roaring from the sea, immediately evacuate.
- While you may not be caught in a tsunami, emergencies can happen, so it is important to be prepared.
Here are a few key tips in case of an emergency:
- o Learn about disasters and how to keep safe
- o Create and practice a household emergency plan
- o Assemble and maintain emergency survival items
- o Have a getaway kit in case you have to leave in a hurry
- For basic tips on how to prepare for an emergency visit aucklandcivildefence.org.nz
Orewa Seawall – There Goes the Beach
There has been quite a bit of movement to get a seawall built along the Orewa beach front in order to stop erosion going back to “valuable” properties situated there. Except rather having the sea wall to protect properties that should have never been placed there in the first place the community should be looking at what is called soft-engineering solutions. That is rather than a seawall they should build natural sand dunes and plant them out.
Because the hydraulic action caused by wave reflections off hard seawalls actually lower the beach floor until sea level comes right up to the wall permanently – aka no more beach for Orewa. Where as soft engineering solutions like sand dunes acts as both as brakes/shields and a home to native coastal wildlife without the lowering of the beach floor you see with seawalls.
Seawalls are vertical or near vertical shore-parallel structures designed to prevent upland erosion and storm surge flooding. Seawalls are generally massive concrete structures emplaced along a considerable stretch of shoreline at urban beaches. The term “sea wall” is commonly used to describe a variety of shoreline armoring structures including revetments.
For as long as humans have lived along coastlines, they have made attempts to mitigate the effects of erosion and tame or defend against the natural elements to improve the safety of their homes and other buildings. The history of seawalls dates back thousands of years. Shorelines provide many advantages to cultures and societies, serving as abundant food sources with fish, crab, clams and other sea creatures, as well as providing access to transportation and shipping to and from distant lands via the natural highways which are the world’s oceans.
Impacts of Seawalls on Beaches
Building a seawall on a beach has several inevitable impacts and additional potential impacts.
- Passive erosion – Wherever a hard structure is built along a shoreline undergoing long-term net erosion, the shoreline will eventually migrate landward to (and potentially beyond) the structure. The effect of this migration will be the gradual loss of beach in front of the seawall or revetment as the water deepens and the shoreface moves landward. While private structures may be temporarily saved, the public beach is lost. This process of passive erosion is a generally agreed-upon result of fixing the position of the shoreline on an otherwise eroding stretch of coast, and is independent of the type of seawall constructed. Passive erosion will eventually destroy the recreational beach area unless this area is continually replenished. Excessive passive erosion may impact the beach profile such that shallow areas required to create breaking waves for surfing are lost.
- Placement loss – Seawalls are placed on the beach. In many cases, construction of seawalls is on public property (beach), which is then lost. An example is in Solana Beach, California, where most land for seawalls is leased free of charge to the property owners. This is a taking of extremely valuable public property.
- Active Erosion – Refers to the interrelationship between wall and beach whereby due to wave reflection, wave scouring, “end effects” and other coastal processes the wall may actually increase the rate of loss of beach. This is site-specific and dependent on sand input, wave climate and other local factors.
- Public access impacts – these can be a result of passive erosion, placement loss or active erosion. Seawalls built on eroding beaches will lead to the loss of access.
- Visual/aesthetic impacts – Seawalls are generally not attractive and can detract from a natural beach experience.
- Economic issues – local, state or federal subsidies or construction to protect private property, or insurance coverage. Construction is performed on State or Municipal land. The public is typically not compensated for this loss of valuable property.
- Loss of sand supplied by eroding bluffs that are armored. A minimal fee for this sand is collected from property owners for the sand that would provide beach material. Additionally, the eroded area would create a beach. Generally, there in minimal or no compensation to the public for the loss of sand and beach.
- Ecological impacts – scientific studies have documented a loss of ecosystem services, loss of habitat and reduction in biodiversitywhen seawall-impacted beaches were compared to natural beaches. Also see here and additional references below.
The most important thing to remember is that a seawall is never built to protect the beach. Rather, it is built to protect property, structures or a cliff from erosion.
And from Wiki on Soft Engineering:
Unlike hard engineering where typically has no habitat value for fish or wildlife, soft engineering incorporates habitat for fish and wildlife. The Detroit River is one of the most biologically diverse areas in the Great Lakes Basin. In 1998, the U.S.–Canada State of the Lakes Ecosystem Conference (SOLEC) identified the Detroit River–Lake St. Clair ecosystem as one of 20 Biodiversity Investment Areas in the entire Great Lakes Basin ecosystem with exceptional diversity of plants, fish, and birds, and the requisite habitats to support them. The State of the Lakes Ecosystem Conference went on to call for special efforts to protect these unique ecological features. Many people who appreciate the outdoors know that the Detroit River supports a nationally renowned sport fishery. For example, the City of Trenton, located on the Trenton Channel at the lower end of the Detroit River, hosted a major walleye fishing tournament called “Walleye Week” in 1999. “Walleye Week” attracted people from all over North America to compete in the In-Fisherman Professional Walleye Tournament, the Team Walleye Tournament, and the Michigan Walleye Tournament offering $240,000 in prize money. It is estimated that walleye fishing alone brings in $1,000,000 to the economy of communities along the lower Detroit River each spring.
Another reason why soft engineering practices should be encouraged is because it is well recognized that there is limited public access to the Detroit River, particularly on the United States side. Use of multiple-objective soft engineering of shorelines will increase public access to the river.
There are also economic benefits associated with use of soft engineering. In general, soft engineering of shorelines is typically less expensive than hard engineering of shorelines. Additionally, long-term maintenance costs of soft engineering are generally lower because soft engineering uses living structures, which tend to mature and stabilize with time.
Soft engineering in my opinion as a Geographer would be the way to go for Owera.