This project is designed to reduce the risk of levee failure by about an order of magnitude from the 10-year to the 100-year level.
10-year versus 100-year levels
The 10 and 100-year tidal water surface elevations are statistical. Every year has a 1% chance of experiencing a 100-year event and a 10% chance of experiencing a 10-year event. Over the next 30 years, a 10-year flood has a 95.8% chance of occurring and a 100-year flood has a 26% chance of occurring.
According to FEMA’s water surface elevation analyses and United States Army Corps of Engineers’ depth-damage functions:
- A 10-year flood would cause over $13 million in damage to Santa Venetia
- 100-year flood would bring that cost to over $32 million
FEMA’s benefit-cost analysis system uses an algorithm that considers these damages and probabilities. According to that system, the proposed Santa Venetia levee upgrade project would result in a damage savings of $27 million over a 30-year period. The project is estimated to cost $6 million.
This presents a benefit-cost ratio of approximately 5:1.
This damage estimate does not take into account further sea level rise, which is expected to also increase frequency and damage due to flooding events.
FEMA and the National Flood Insurance Program estimate that 1 inch of water in your house can cause $25,000 of damage. Use the elevation map and damage estimator to see what a 10-foot tide could cost you.