The lowering of water level along a coast when offshore winds push water seaward, the reverse of wind setup. It is also called negative surge and appears as a negative residual. Set-down can leave less water than charted at low tide, a hazard for deep-draught ships, and in shallow bays it exposes large areas of bottom. The same storm often brings setup on one side of a bay and set-down on the other.
Set-down of 0.6 with this northwester, so the predicted low will go well below chart datum.
Also heard as
- setdown
- negative surge
- wind setdown
Related terms
Storm surge
A rise of water above the predicted tide caused by a storm's winds and low pressure.
Blowout tide
An extreme low water caused by strong offshore winds pushing water out of a bay or sound.
Residual
The observed water level minus the predicted tide, showing the effect of weather, rivers and other non-tidal causes.
Minus tide
A low tide predicted to fall below the chart datum zero, shown as a negative number in the tide table.