Time Series for Storm Indices, Winter 1996 The three lower traces show different indices of rainfall. Note a small storm early in December, and a LARGE one near January 1. The upper trace is a rough indication of the mean water level in Three Mile Slough; note that flooding starting about Dec. 8. The upper red trace is the rms signal strength. It starts to decrease about when the flooding starts. However, this may be due to other effects than absorbtion by suspended sediment.