The Coastal Property Boundary in California: Recommendations to Improve Determination of the Mean High Tide Line in Light of Sea-Level Rise.

• Author: Garlock, Jennifer

Table of Contents Introduction A. Defining the Mean High Tide Line B. Challenges Due to Sea-Level Rise I. Current Methodology for Determining and Locating the MHTL A. Tide Data Used to Determine the MHTL B. Procedure for Locating the MHTL on Land II. Common Law Principles and Statutory Provisions Relevant to a Rising MHTL A. Public Trust Doctrine B. Constitutional Takings Doctrine C. Rule of Accretion D. Public Nuisance E. California Coastal Act III. Challenges With the Current MHTL Determination A. Tidal Datums are Backward-Looking and Outdated B. Sea-Level Rise is Accelerating IV. Compliance With the Law and Sound Coastal Management Policy Requires Determination of the MHTL Using Current Data and Without Regard to Armoring Structures A. The Determination Should be Based on Current Tidal Data B. The MHTL Should Be Located Without Regard to Armoring Structures 1. The Coastal Property Boundary May Not Be Fixed 2. Locating the MHTL Landward of an Armoring Structure Will Not Lead to a Constitutional Takings Claim 3. There is No Absolute Right to Protect One's Property Conclusions and Recommendations Introduction

With a highly developed coastline in California, the matter of where private property ends and State-owned tidelands begin is a critical one. The rate of sea-level rise due to climate change is accelerating, and disputes around the location of this boundary are likely to become more common. (1) Attempts to plan for sea-level rise and mitigate the resulting harm to both coastal properties and public beaches are proving to be highly controversial. The City of Del Mar has opposed the California Coastal Commission by rejecting any incorporation of "managed retreat" in its Local Coastal Program, instead saying the City will rely on sea walls and sand replenishment to protect structures and beaches. (2) The Commission and private property owners are increasingly waging court battles over the continued existence of protective sea walls; the Commission recently voted to require a Laguna Beach property owner to tear down its sea wall and also pay a one million dollar fine. (3) Determinations of whether or how upland owners may develop their property (4) will need to consider sea-level rise, and the location of the property boundary will play an important role in these decisions.

This Comment starts by defining the property boundary and identifying why sea-level rise presents a challenge. Part I explores the nature of how the property boundary is currently determined, while Part II identifies legal principles that apply to this determination. Part III identifies two main technical challenges in locating the property boundary in a world of increasing sea-level rise: the outdated nature of tidal data used to determine the boundary, and how to locate the boundary when an armoring structure is present. (5) Part IV argues that in order to comply with the law and enact sound coastal management policies, the mean high tide line (MHTL) should be determined using up-to-date tidal data and should be located without regard to armoring structures. Finally, the conclusion advances recommendations for developing this more technically and legally sound approach to determining the MHTL.

1. Defining the Mean High Tide Line

   California law provides that the State owns all land below the "ordinary high water mark." (6) The "ordinary high water mark" is to be determined by the average height of all high tides at a given location over a period of 18.6 years. (7) This is referred to as the mean high water mark, or MHTL.

   The MHTL is an ambulatory boundary with two major causes of movement. First, the boundary moves as the shore changes, either due to erosion and accretion (horizontal changes) or due to vertical land movement. (8) Second, the MHTL can move as the elevation of the water changes, as is the case with sea-level rise. (9) The legal boundary is the point at which the MHTL intersects the shore, and can only be approximated, but not legally fixed, when drawn as a meander line on a survey map. (10)

   The public trust doctrine provides that the sovereign holds certain natural resources in "trust" for current and future generations and may not transfer those resources to private parties or allow their injury or destruction. (11) Land below the MHTL (tideland) is held in the public trust, while land above the MHTL (upland) may be privately owned. (12) As the MHTL moves landward, due to subsidence of the land or erosion of the shore, the newly submerged lands below the MHTL belong to the State. (13) Similarly, if the MHTL moves seaward, due to uplift of the land or natural accretion on the shore, those newly uncovered lands belong to the upland property owner. (14) The tension between coastal private property rights and the State's duty to protect tidelands held in the public trust will increase as sea level rises and moves the MHTL landward. The legal obligation caused by this landward migration will clash with the expectations of property owners about the extent of their property and what they may do with it.

2. Challenges Due to Sea-Level Rise

   The coast has always been dynamic, with shorelines subject to change by wave action and storms. However, development has proceeded assuming some amount of stability in the land area. (15) Going forward, the impacts of climate change on the coast will include not only sea-level rise, but also changes in the frequency and strength of storms battering the coast. (16) Changing conditions call into question the expectations of coastal property owners about the extent of their property and its use. (17) Property owners may increasingly attempt to construct coastal armoring structures to protect their property from sea-level rise, increased erosion, and more frequent flooding. (18)

   Tide stations in central and southern California have observed sea-level rise of 1-2 millimeters per year, (19) with projected rates increasing. (20) For context, on a relatively flat beach, one centimeter of sea-level rise will result in a forty-centimeter horizontal landward movement of the ocean/beach interface. (21)

   Even under conservative estimates (assuming drastic reductions in global greenhouse gas emissions), sea-level rise and the resulting impacts on coastal property will be significant in the decades to come. (22)

   California courts have not directly applied the principle of an ambulatory boundary to changes in the MHTL due to sea-level rise, but the matter has been contemplated in dicta. In Littoral Development Co. v. San Francisco Bay Conservation and Development Commission, the court noted that if sea level does rise due to global warming, so will the MHTL, and with it, the jurisdiction of the local planning commission. (23) Such a finding would be a "logical extension" of the well-established principle that the boundary is ambulatory. (24)

   1. Current Methodology for Determining and Locating the MHTL

   The National Oceanic and Atmospheric Administration (NOAA) provides the underlying data for the MHTL calculation from tidal stations on the Atlantic, Gulf, and Pacific coasts. While the data provided by NOAA is nationally uniform, procedures for identifying the MHTL boundary may vary by jurisdiction. This Comment is only representative of California's procedures.

1. Tide Data Used to Determine the MHTL

   NOAA provides tidal datums for each of the twelve active tide stations along the coast of California. (25) Tidal datums represent a sea level elevation calculated from tidal data over a nineteen-year period, and include the MHTL, Mean Sea Level, and Mean Low Water. (26) The tidal datums provided by NOAA are based on a vertical datum and tide measurements taken over the National Tidal Datum Epoch (NTDE) period. The same NTDE is used at tide stations throughout the United States for uniformity. (27)

   The current vertical datum, a reference point for elevations, is the North American Vertical Datum of 1988 (NAVD88). (28) The fixed base-elevation for a tide station is called the "station datum," and all other tidal datums are measured from this point. (29) The station datum using NAVD88 is based on surveys representative of elevations in 1988. Thus, NAVD88 does not account for any changes in land elevations due to uplift or subsidence since that time.

   The NTDE is published by NOaA's National Ocean Service (NOS) and is based on tidal measurements over a nineteen-year time period, currently 1983-2001. (30) A nineteen-year time period is used to cover an 18.6-year astronomical cycle, which includes all significant variations in the tides based on the relative locations of the moon and sun to earth. (31) Collectively, the tidal measurements over this period and the station datum provide the data necessary to calculate the tidal datums used in locating onshore boundaries, such as the MHTL.

   The NTDE is updated every twenty to twenty-five years to capture changes in mean sea level (MSL) and vertical land movement. (32) The basis for this frequency of NTDE update is to limit changes in MSL between nineteen-year epochs to 0.03 to 0.05 meters (approximately 0.10 to 0.16 feet) at most stations. (33) NOAA notes that, given predictions of accelerating rates of sea-level rise, updates more frequently than twenty to twenty-five years may be required. (34)

2. Procedure for Locating the MHTL on Land

   The MHTL is not a fixed geographic or physical location, and the point at which the plane of the MHTL intersects the land can only be approximated by surveying. (35) It is important to recall, however, that this surveyed meander line cannot fix the property boundary, and the "true property boundary remains the watercourse." (36) The point at which the MHTL elevation intersects the shore depends on the slope and elevation of the beach and will vary by season. (37) Therefore, a survey of the MHTL location represents only a snapshot in time.

   The State Lands Commission (SLC) has exclusive jurisdiction over tidal and submerged lands...