نطق چهارم

Listen to part of a lecture in an environmental science class

Before we get started, I want to tell you a little story.I guess it was about 10 years ago, I decided, with my family, I decided it was time to buy a house and my two kids really wanted a house near the ocean, as close to the beach as possible. Well, I tried to explain all the reasons that building near the ocean just didn’t make sense environmentally, but the kids still wanted a house near the ocean. So, my wife and I looked at a few houses and they were beautiful. There was one we saw that I still call our family’s dream house. But we were lucky, and I’ll tell you why in a moment, when we realized that we just couldn’t afford any of those houses.

So I said building near the ocean doesn’t make sens e environmentally, but what is it about the coastal environment that makes most of the land there unsuitable as a building site? Let me explain coastal zones first.

Imagine standing at the water’s edge and moving away from the ocean.We come across different coastal zones.Going in order they are: the beach, which I’m sure you’re all familiar with, second is the primary dune, which is the most fragile zone.Next is the trough. That’s trough, T-R-O-U-G-H.After the trough is the secondary dune and finally you come to what’s called the back dune.

So, the beach, if I say it’s not advisable to build houses on the beach, right on the shoreline, I don’t think you’d find it difficult to imagine why. You got the sand, which is not very supportive for building and you got daily tidal fluctuations.Keep ) in mind too that the sands are always shifting and the shoreline is moving.

Right near here you got Sandy Peninsula and you can walk out on that peninsula almost a mile, to Sandy Point, but it wasn’t that long ago, I think back when my grandfather was a boy, that Sandy Point was an island and you couldn’t walk there from the main land right?

The sands shift and the shorelines move.Before we continue this imaginary walk, I want you to think for a minute. Why are these coastal zones important? Well, environmentally, their role is protecting the inshore areas from being flooded with salt water, from being damaged during storms and they allow vegetations to grow further inland by providing sort of a buffer zone, to protect against wind and salt spray.

Alright, let’s go back to our walk on the beach.Okay, after the beach I said you’ve got the primary dune. Now, you shouldn’t build on the beach but it’s okay for recreation.That’s good. But the primary dune really cannot support building or recreation. It’s more sensitive than the beach.

If you think of a sand dune as just a windblown pile of sand, that’s wrong. Sand dunes can support vegetation and the primary dune is where vegetation first begins to take hold, but it’s fragile and easily disturbed.And what happens when the vegetation is disturbed is that the sand dunes from the beach can migrate inland leaving less sand on the beach, and less sand on the beach, well that’s beach erosion. You’ve probably seen beaches which used to be very wide that seem to be shrinking. Beach erosion is often caused by destroying the primary dune. After the primary dune we come to the trough.

Now, the trough is tolerant of limited recreational use and some building. The vegetation is thicker and the ground more stable. Care should be taken to preserve the quality of the ground water, but in general it’s ok to build here. After the trough is the secondary dune.

This is sort of the final defense against the sea and like the primary dune, no building should take place here.The last zone we’ll look at is the back dune. It’s further inland and more suitable for development than any of the other zones. So, the first two zones we looked at, the beach and the primary dune, are probably the worst places for building and where do people most want to build? Exactly! The beach and the primary dune.We’re talking about very valuable real estate, right on the ocean!

I mean to build on the beach, today you may be a hundred meters from the water’s edge and in a few years the water’s edge may be right in your living room. And that’s what happened to our dream house. A storm brought the water’s edge right up to the house.Afterwards, the water receded but the action of the waves removed so much sand that the house was now unstable. It was now impossible to live in this beautiful and very expensive house.