NEW ORLEANS (AP) — Waves crashed high against flood walls Monday and New Orleans' rebuilt levee system survived its first hurricane in three years, but Gustav exposed weaknesses the Army Corps of Engineers won't plug any time soon.

Gustav was no Katrina. It was smaller, and the worst rain and wind missed New Orleans. Its storm surge — between 10 and 15 feet lower than Katrina's — entered New Orleans through navigation channels in the east and washed over the Industrial Canal.

The Industrial Canal has been characterized as the Achilles heel in the system, and the corps is spending $700 million on a barrier at its mouth to stop surges. But the barrier won't be in place until at least 2011. On Monday, water overtopped parts of the canal's flood wall causing minor flooding.

Another major weakness in the flood protection system is in the area known as the West Bank, where about 250,000 live. Work on the West Bank is far from complete. The corps has repeatedly said it may be the city's weakest flank.