If you’re a buyer interested in coastal waterfront property, you may have heard or seen the term “mean low water” or “MLW.” You may also have heard about “mean high water” or “MHW.” These water level indicators are relevant when looking for property along any body of water affected by the ebb and flow of tides. But what do they mean?
What causes fluctuations in MLW?
Mean low water and mean high water are affected by the changing tides, the periodic rise and fall of seawater in relation to a fixed reference. Most of us know this phenomenon is caused by the gravitational pull of the sun and the moon over Earth’s waters. However, many variations can occur based on the actual positions of these celestial bodies in relation to Earth and other environmental factors, like wind and weather. The mean high tide and mean low tide are determined using the average of these levels in a given location over time, known as the National Tidal Datum Epoch — a time span of 19 years.
Why is MLW important to property owners?
The special rules related to property owned adjacent to a standing body of water like an ocean, bay, delta, sea, or lake are known as littoral rights. The rules related to flowing water like streams or rivers are riparian rights.
Rising tides and property lines
The reason for shifting sea levels is up for debate, but there’s no question that these levels are rising, which poses a problem for coastal real estate, like Annapolis waterfront properties. When land is entirely and permanently submerged under tidal waters, homeowners may literally lose ground. Although some homeowners may build structures to protect littoral property from encroaching sea levels, some designs are limited by state and local regulations. Who officially owns the diminishing property can vary significantly between states — and so can their options when it comes to protection.
Know before you buy
Waterfront properties are beautiful, but they have some unique issues for potential home buyers. A well-informed buyer can avoid any surprises by knowing what rules apply to the specific waterfront property they’re like to purchase. In addition to making sure you’re well-versed in local tide levels and littoral rights, some other things to consider when looking at waterfront properties include:
Access—Make sure the property you’re interested in has access rights and the extent of that access.
Environmental restrictions—If the desired property is near tidal waters or wetlands, there may be some restrictions on landscaping or building plans. Be sure to do your research.
Water depth—In addition to knowing where property begins and ends, water depth is also necessary to know for boating options, dock placement, or other shoreline construction.
Flooding—Request a copy of the property owner’s elevation certificate and run it by your insurance company to determine risk and insurance expense.
- Mean low water or MLW: The average water level at low tide
- Mean high water or MHW: The average water level at low tide
- Littoral rights: The special rules that relate to property owned adjacent to static water like an ocean, bay, delta, sea, or lake
- Riparian rights: The special rules that relate to property owned adjacent to flowing water like streams or rivers
- National Tidal Datum Epoch: 19 years (rounded up from 18.6 years) that span the entire celestial course the moon follows in relation to the earth