As described previously, tide tables are merely estimates calculated by averaging the highs and lows for the last ten years and projecting them forward for the coming year(s). During periods of rain, tide tables must be adjusted to higher levels than forecast. Here is a high water level forecasting tool that can help you determine if your parking lot, walkways or other areas are likely to flood.
How to use this Forecasting Tool: first, measure or otherwise determine the water level at which your parking lot starts to flood, i.e. the Flooding Level.
Check the expected high tide for the next day on your tide app or on the interactive tide chart on the right side of the Floating Times. (There are two highs per day, so be sure you have the higher of the two.) Next get the rain forecast for the eight hours before the higher tide. If the hills are dry add about an inch for every expected inch of rain, but if the hills are super saturated, you’ll need to add up to eleven inches for every inch of expected rain, because the drainage area of the surrounding hills is 11 times the area of the Bay.
Examples: Dry Hills (or) Saturated Hills with heavy runoff
Forecast High Tide 6′ 2″ 6′ 2″
Forecast Rainwater 1″ 11″
Rainwater plus Tide = 6′ 3″ 7′ 3″
— Parking Lot Flooding Level XX XX XX XXm
= Amount of Flooding __________ __________
Copy this one to use in real time:
Dry Hills Super Saturated Hills
Forecast High Tide ____________ ____________
Forecast Rainwater ___________ ____________
Rainwater + Tide _____________ ____________
– Parking Lot Flooding Level _________ ____________
= Amount of flooding __________ ____________
The need for additional resurfacing of the parking lots to offset the increasing tide levels is accelerating. Recently the county cut a trench across our parking lot here at Yellow Ferry Harbor to lay a water line: the cut showed that our parking lot asphalt is 12 inches thick! There will be more over-paving to come!
Flash: Super high tides are due again January 10-12 and February 8-9.