People who have resided in North Wildwood for their entire lives generally know what to expect when a Coastal Flood Advisory is issued and how to protect their vehicles and property. In this post, we will cover flooding, both tidal and from the rain. To understand why we flood we first have to cover some basic facts about our location. North Wildwood is built on a barrier island; as an island, some areas are higher than others. In North Wildwood the elevation of the ground surface heading west starts at sea level at the beach to a higher area on Surf and Atlantic Avenues and then the elevation goes downward back to sea level at the back bay. There is another high area in the north end around the Beach Colony area. When looking down a street the elevation change is hardly noticeable but based on some of the water levels on Delaware Avenue the rise is more than 3 feet. A good illustration of the elevation difference is new construction. All new construction has to be at 10 plus one feet above the base flood elevation. This elevation is figured using the Datum NAVD88 which is different from the Datum MLLW used for tides so don’t confuse this elevation with the tide heights we post. Nonetheless, in new homes on Delaware Avenue, the first floors are over four feet above ground; in the same new homes on Surf Avenue, the first floor can be one foot above ground. To learn how to figure the tide height compared to your home’s first floor height we created a document explaining it. It’s available in the links on the left-hand side if you are reading this online, if you are reading this as an email click HERE to download the document.
Flooding from Rain – In 2023 flooding from rain caused the city to send a Code Red Message 30 times. Why does rain cause flooding? The main reason is that the rain comes down faster than the water can drain off or be absorbed into the ground. When it rains continuously the ground becomes saturated and the rain has nowhere to go but down your driveway to the gutter in front of your house. The water in the gutter using gravity travels to the lowest point and in most cases is Westward until it reaches a cross-street. At the cross-street, the water goes down the storm drain under the roadway and up to the storm drain on the west side of the cross-street. This is called the “bubbler system” where the water that goes down the storm drain comes up the other side and will try to rise to the height of the water on the east side. As the west side is lower than the east side the water runs down the gutter westward until it reaches the next cross-street and the process happens over again until the water reaches the last storm drain and instead of coming up the next storm drain the water drains out a back bay outfall pipe. On the end of the outfall pipe is a flapper valve also known as a duckbill valve. This valve is a one-way valve allowing water to exit out but not come in. This is why rain runoff drains slower during high tide as the tidewater pushes against the flapper keeping it closed or at least a reduced flow. We have had situations where after a rain storm stopped an hour earlier there was flooding on the west side caused by rain runoff that continued to Delaware Avenue and was not able to exit the outfall pipes due to high tide. We sometimes get flooding from rain on the East side of New Jersey Avenue after heavy rainfall, this is caused when the amount of water trying to travel through the storm drain exceeds the volume that can be pushed through the storm drain by gravity.
Tidal Flooding – Twice a month during the full moon and new moon (14 days apart) we get the highest tides. Generally, none of the full moon or new moon tides will cause flooding on its own. However, when we get persistent Northeast winds, that hold the tide back, which will cause a compounding of tides, where the tide doesn’t go all the way down and the next tide rises on top it even higher we can get minor tidal flooding. When it’s combined with a coastal storm with winds and rain we get even higher tides. From our experience when the tide reached 6.2 feet above MLLW (Mean Low Low Water) we started to see water around the storm drains on Delaware Avenue, sometimes on North Delaware, and even some storm drains on New York Around 3rd Avenue. It is not always the same every time the tide reaches a certain height as the winds are different in speed and direction and there have been occasions when debris gets stuck in an outfall pipe flapper valve or the flapper valve is damaged which will allow water to come in. When the National Weather Service issues a Coastal Flood Advisory it means the tides could be anywhere from 6.0 to 6.9 feet (Minor Flooding). For Moderate and Major tidal flooding they will issue first a Watch and then a Warning. The Coastal Flood Advisories will have the “Departure from Normal” for Cape May and Ocean City which will show how many feet the prevailing weather will cause the tide to reach above the predicted tide that is posted annually. They do not post a departure from normal for every town in the county so to get an idea of what we can expect we do the following – Check the departure from normal for Cape May and Ocean City. As we are somewhere in the middle we look to see whether Ocean City is trending higher or lower than Cape May. Most times Ocean City is lower than Cape May so we then take the Departure from Normal for Cape May and add it to the predicted tide for our area. Not always accurate but it gives us an idea of what to expect so we can be prepared.
Flood warnings – The first notice of possible tidal flooding comes from the National Weather Service in the form of a Coastal Flood Advisory. Many times we will give advance notice on our Facebook Page. If we have a Coastal Flood Warning (Moderate or Major) we will send a specific Code Red Message to alert residents of the upcoming tides. When the North Wildwood Police Department observes water in the gutters exceeding the curb height (six inches) in two locations in different areas of town (not in the same block) they will send a Code Red Message for either Street Flooding from the Rain or Tidal Flooding. On some occasions when the town is crowded and many people may not get the Code Red Messages on their phones the Flood Warning Siren is sounded. Also sometimes due to heavy rain at high tide a message for tidal flooding is sent when it should have been a message for Flooding from Rain. To educate the public on our Facebook Page after we send a Code Red Message for flooding, we post either the rainfall amount or tide height so that residents can familiarize themselves with what to expect when they hear a prediction of a certain amount of rain or predicted tide heights. North Wildwood has a Tide Gauge and Weather Station that can be viewed by clicking on a link located in the left-hand column of this website. There are also other helpful weather links on this page. If you are reading this as an email the website is HTTP:/ready.northwildwood.com.