IN 2005 the last of the concrete was poured for Lismore's $18,900,000 flood levee.

It is a 3km long wall, up to 11.56m high in parts and designed to protect the central business district from flooding.

"If the wall was there 60 years ago, there would have been about five floods that made it into the CBD,"  Rous Water general manager Paul Muldoon said at the time.

Then Lismore mayor Merv King said it was the 1989 flood that finally led to considering a century-old idea and the city saying 'enough is enough, let's build a levee'.

The flood levels peaked at 11.2m that year. A major flood but it still not as major as the 1954 and 1974 floods when flood levels reached 12.11m.

Lismore City Council

"It's not designed to flood proof Lismore, it's designed to protect it from what we call the one-in-10-year flood," Mr Muldoon had said.

He also said no one would know for certain how well the levee would work until the next flood.

"It will be a nervous time to see exactly what happens and how it works. But in any type of flood there will now be a certain level of protection."

And it did.

In 2009 flood levels reached 10.4m. But thanks to the levee, the CBD was safe. And for eight years it has remained uncompremised.

Until now.

Lismore is officially seeing its highest flood since 1974, reaching 11.53m just after 9am this morning, and still rising.

At 4.15am, a siren sounded for the first time in 12 years as water spilled over the levee and inundated the CBD.

Residents were told to evacuate immediately.

Lismore City Council

In 2005, Mr Muldoon said if water does rise above the levee, its first entry point will be near the Lismore Police Station in Molesworth Street.

It would then flow down the Browns Creek floodway, along the back of Woodlark Street and settle in the Lismore 'basin', in the Dawson Street area.

The Lismore levee has successfully directed water into the CBD via a pre-planned route down Browns Creek to Dawson St, which is now completely underwater.

Excess floodwater has travelled down Molesworth St and turned left at Woodlark St, continuing down to Dawson St.

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