California Coastal Commission

Report on In-Lieu Fee Beach Sand Mitigation Program:
San Diego County

January 1997
(revised September 1997)

principal author sherilyn sarb
with technical assistance by lesley ewing
in consultation with amy roach, staff counsel
 
prepared under the direction of charles damm

FINANCIAL ASSISTANCE FOR THE PREPARATION OF THIS DOCUMENT WAS PROVIDED BY THE COASTAL ZONE MANAGEMENT ACT OF 1972 — AS AMENDED — ADMINISTERED BY THE OFFICE OF OCEAN AND COASTAL RESOURCE MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION.


 

Table of Contents

I. PURPOSE OF THIS REPORT

II. MITIGATION OF IMPACTS TO SAND SUPPLY

III. THE BEACH SAND MITIGATION PROGRAM — SAN DIEGO COUNTY

A. INITIAL APPLICATION

B. METHODOLOGY TO QUANTIFY IMPACTS AND CALCULATE FEE

C. METHODOLOGY BASED ON SCIENCE

D. APPLICATION OF MITIGATION PROGRAM IN SAN DIEGO COUNTY

IV. RECOMMENDATIONS FOR USE OF THE MITIGATION PROGRAM IN OTHER LOCATIONS

V. REFERENCES

VI. ATTACHMENTS

ATTACHMENT 1: IMPACT ANALYSIS FOR SHORELINE PROTECTIVE DEVICES

ATTACHMENT 2: MEMORANDUM OF AGREEMENT BETWEEN SAN DIEGO ASSOCIATION OF GOVERNMENTS AND THE CALIFORNIA COASTAL COMMISSION

ATTACHMENT 3: BEACH SAND MITIGATION FUND


I. PURPOSE OF THIS REPORT

The Commission’s Regional Cumulative Assessment Project (ReCAP) in its December, 1994, "Preliminary Findings and Recommendations" documented that large sections of the pilot Monterey Bay shoreline were being armored through emergency and regular permits for individual site protection. The ReCAP findings and other staff work contributed to a growing body of evidence that armoring a bluff, in addition to encroaching onto the beach and preventing its further landward migration, will reduce the amount of sand and gravel entering the littoral cell, and will cause the narrowing of an eroding beach over time and reduction in the area of sand available for recreational use.

This report is initiated through a Project of Special Merit which was implemented in San Diego County and funded through a Federal grant from the Office of Coastal Resource Management (OCRM). The objective of the Project of Special Merit is to lay the foundation for a comprehensive regional approach to regulating shoreline development, which takes into consideration the cumulative adverse impacts of shoreline armoring on the long-term availability of sandy beach areas for public recreational use. This report is a product of the San Diego project, along with two procedural guidance documents to be used in evaluating proposals for shoreline protection.

Used in conjunction with the Procedural Guidance Documents on Review of Permit Applications for Shoreline Protective Devices and on Monitoring, this report will help provide a framework for Commission staff to assess the adverse and cumulative impacts of shoreline protective devices on shoreline sand supply, and therefore, on public access and recreational opportunities. The contents of this report is technical as it contains a methodology which can be utilized to quantify the adverse effects of shoreline armoring. In addition, all of the above referenced documents identify potential measures which can be implemented to mitigate such identified effects.

The specific purpose of this report, pursuant to the requirements of Task 1.3.B of the Commission’s FY 95 federal grant, is to identify the components of the in-lieu fee beach sand mitigation program which has been implemented in portions of San Diego County through the Coastal Commission’s approval of coastal development permits for seawalls in the City of Encinitas and Solana Beach. The report is to analyze the application of the in-lieu fee as a condition of approval of other projects in different shoreline situations. The objective is to develop a complete program for implementation within San Diego County and to identify the constraints or limitations to implementation in other shoreline areas along the California coast.

II. MITIGATION OF IMPACTS TO SAND SUPPLY

Section 30235 of the Coastal Act requires the Commission to approve seawalls, revetments, cliff retaining walls and other such construction that alters natural shoreline processes to protect existing structures, public beaches and coastal development uses in danger from erosion and when designed to eliminate or mitigate the adverse impacts on shoreline sand supply. The Coastal Act does not contain a specific definition for mitigation. The California Environmental Quality Act (CEQA) guidelines provide a definition of mitigation for purposes of CEQA. Section 15370 of the CEQA guidelines define mitigation as:

1) Avoiding the impact altogether by not taking a certain action or parts of an action.

2) Minimizing impact by limiting the degree or magnitude of the action and its implementation.

3) Rectifying the impact by repairing, rehabilitating, or restoring the impacted environment.

4) Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action.

5) Compensating for the impact by replacing or providing substitute resources or environments.

This definition provides several alternative forms of mitigation. In mitigation by avoidance, adverse impacts are avoided altogether through alteration of project location, design, or other related aspects. Commission staff typically recommends mitigation by avoidance, if feasible, since it is the best way to prevent direct adverse impacts to public access and sand supply in association with a shoreline protective device. However, if the Commission is required to approve a shoreline altering device to protect an existing structure in danger from erosion, minimizing, rectifying or reducing project impacts are forms of mitigation that diminish the severity of the project related impacts and are required under Section 30235. Although these forms of mitigation can result in alterations to the project design, the overall integrity of the project can be preserved.

Compensation includes mitigation undertaken to replace public access or sand which is lost or adversely impacted, with access or beach of equal or greater value or size. This report is examining the use of a fee, instead of placing sand on the beach, to compensate for the impacts of seawalls on natural shoreline processes and sand supply in San Diego County. The analyst should refer to the Procedural Guidance Document on Review of Permit Applications for Shoreline Protective Devices to identify other forms of mitigation which may be appropriate when recommending approval of shoreline altering devices. As further addressed in the above referenced document, mitigation can take a variety of forms depending on various factors, including the nature of the impact, the amount of beach available, the ability to revise the proposed project and ownership of the land.

III. THE BEACH SAND MITIGATION PROGRAM — SAN DIEGO COUNTY

A. Initial Application

The Coastal Commission initiated the in-lieu fee mitigation program in response to two coastal development permit applications for lower bluff protection in the City of Encinitas in San Diego County. One application involved the construction of 9-ft high shotcrete seawalls, with tiebacks, on public property fronting six non-contiguous lots to protect existing private residential blufftop development (CDP #6-93-85 Auerbach et al). The second application was for similarly designed seawalls in the nearby section of shoreline on 8 contiguous properties (CDP #6-93-131 Richards et al). The projects represented the first proposals for armoring along a section of coastline backed by 100 foot high, very scenic coastal bluffs, where the vertical portion of the bluffs are owned by the City of Encinitas.

These public coastal resources, i.e., the bluffs, had not been altered by stairways, retaining walls, seawalls or other forms of protective devices which exist along other segments of the Encinitas shoreline. The requests were being made to stop the natural process of undercutting in order to prevent massive block falls. Some of the properties had experienced sloughage of the upper bluff which had precipitated the initial concern and prompted the permit applications. Additionally, landowners of five properties requested permits for installation of a below-ground, upper bluff retention systems, to secure the residences in the event the upper bluff should continue to erode to the point of threatening the foundation of the structures.

Pursuant to Section 30235, the Commission is required to approve a protective device which alters natural shoreline processes, such as the proposed seawalls, when there is an existing structure in danger from erosion and a seawall is required to protect it; and, when the protection is designed to eliminate or mitigate adverse impacts on shoreline sand supply. In the Encinitas examples, it was determined that protection was necessary; therefore, some form of mitigation was required, if the structures were approved, to offset the significant effects of the armoring on the adjacent public resources, including beach sand supply, and, therefore, public access and recreational opportunities. The in-lieu fee program was derived as the means to mitigate the impacts of the shoreline protective devices on beach sand supply, to be paid by the applicants in-lieu of placing sand on the beach. The payment of the fee was required as a condition of approval of the coastal development permits for the shoreline protective devices in accordance with Section 30235 of the Coastal Act.

The amount of the fee was derived through a methodology developed by the Commission staff coastal engineer to quantify the amount of sand that would replace the lost beach area and replace the amount of sand denied to the littoral cell over the life of the structure. That volume of sand is then multiplied by the cost of transporting and depositing sand on the beach in the project vicinity to determine the fee to be paid in-lieu of placing sand on the beach to mitigate for the lost beach area and material.

At this time, the condition is specific to permits in San Diego County, because there is a regional agency, the San Diego Association of Governments (SANDAG) that has agreed to collect the fees and administer the fund. SANDAG has adopted a Shoreline Preservation Strategy for the San Diego County shoreline which acknowledges the value of beaches to recreation and tourism and, thus, to the State and regional economy, and encourages beach replenishment to protect property and maintain beaches for public recreational use over the long-term.

As mentioned, the in-lieu fee mitigation program was developed in San Diego County as a result of proposals for shoreline armoring which covered many contiguous properties and are located in areas where the bluff and the beach are in public ownership and without existing armoring. The Commission found the fee to be appropriate for several reasons including, the proposed protective devices were located on beaches used by the public; they were necessary to protect private development in danger from erosion; they would result in adverse impacts to State tidelands; there were no design modifications that would lessen or eliminate the impact; mitigation in the form of a fee would allow beach nourishment to occur in a comprehensive rather than piecemeal manner; and the fee would offset the long-term effects of the armoring on the public beach. The amount of fees required through conditions of approval of permits which have been approved by the Commission to date are shown on Attachment 3.

B. Methodology to Quantify Impacts and Calculate Fee

The methodology used to quantify the impacts and calculate the fee amount for the projects which have already been approved by the Coastal Commission was detailed in the staff reports for those projects. As part of the Project of Special Merit implemented in the San Diego office, Commission staff has considered how the methodology can be used to quantify the impacts of shoreline protective devices in other shoreline situations, and in other locations along the California coast. As a result, the staff engineer has revised the description of the methodology and referenced figures to provide an explanation of the science which is more understandable to the layman; however the equations are the same as those used to calculate the fee for the already approved projects. The revised description and figures are contained below and a revised impact analysis worksheet is attached as Attachment 1. The following methodology can be used to quantify some of the effects of a proposed shoreline protective device on sand supply and natural shoreline processes, and to help identify and support the appropriate measures to mitigate those impacts.

As stated, Commission staff has found that some of the effects which a structure may have on natural shoreline processes can be quantified. By quantifying these effects, an analyst can have a better understanding of the impacts of a proposed project and have a way to compare different project designs. Also, this quantification can provide support for any recommended mitigation conditions. Three of the effects from a shoreline protective device which can be quantified are 1) loss of the beach area on which the structure is located; 2) the long-term loss of beach which will result when the back beach location is fixed on an eroding shoreline; and 3) the amount of material which would have been supplied to the beach if the back beach or bluff were to erode naturally.

Loss of beach area on which the structure is located

Shoreline protective devices such as seawalls, revetments, gunnite facings, groins, etc. all are physical structures which occupy space. When a shoreline protective device is placed on a beach area, the underlying beach area cannot be used as beach. If the underlying beach area is public beach, the public will not be able to use the area the way it had prior to placement of the structure. This area will be altered from the time the protective device is constructed and the extent or area occupied by the device will remain the same over time, until the structure is removed or is moved from its initial location. (The only exception to this would be a structure which can spread or move seaward over time, such as a revetment.) The beach area located beneath a shoreline protective device, referred to as encroachment area, is the area of the structure’s footprint (Figure 4-2).

The encroachment area (Ae) is equal to the width of the properties which are being protected (W) times the seaward encroachment of the protection (E). This can be expressed by the following equation:

Ae = W x E

Long-term loss of beach if the back beach location is fixed.

Seawalls, revetments, gunnite facings, etc. protect the landward or backbeach property by being more resistant to wave action than the natural beach or bluff material. Because of this greater resistance to wave attack, these structures remain where they are placed. On an eroding unprotected shoreline, the natural back beach or bluff migrates landward. A shoreline protective device will halt this landward migration and "fix" the location of the back beach or bluff. If the erosion has been caused by the landward movement of waves and general landward migration of the front beach and wet beach area, the fixed position of the back beach will result in a narrowing of the useable beach. When the back beach location on an eroding beach is fixed, the beach will narrow over time shrinking to a smaller and smaller corridor between the ocean waves and the shoreline protective device. Eventually, the dry beach will disappear and waves will hit the shoreline protective device during all but the most extreme low tide events. This loss of beach occurs because the natural balance between landward movements of the fore beach and back beach or bluff has been changed by the construction of a more resistant back beach structure, preventing the landward migration of the back beach or bluff. In some cases, beach lost will be entirely public beach, i.e., the beach seaward of the mean high tide line is held in the public trust, or the beach landward of the mean high tide line is owned by a local government or other public agency such as State Parks and Recreation. In other cases, the beach lost will be both private and public, i.e., the beach seaward of the mean high tide line is held in the public trust and the beach landward of the mean high tide line is private. In all cases, as the beach narrows, there is a loss of beach sand both seaward and landward of the mean high tide line.

The actual long-term loss is equal to the actual long-term erosion times the width of property which has been fixed by a resistant shoreline protective device (See Figure 4-3). Since the actual amount of long-term erosion cannot be predicted, erosion is approximated by the long-term average annual erosion rate times the number of years that the back beach or bluff will be fixed. The width of the property which has been fixed can be determined from the project design. Since one of the key tests of Section 30235 is whether there is an existing structure in danger from erosion, the long-term average annual erosion rate should be provided by the applicant as information to help the analyst determine whether there is any danger from erosion and whether the shoreline protective device is needed. The same long-term average annual erosion rate which is used to determine whether there is any danger from erosion would be used to determine the approximate amount of beach area which would be lost if the landward erosion of the forebeach is not balanced by the landward erosion of the back beach or bluff.

The area of beach lost due to long-term erosion (Aw) is equal to the long-term average annual erosion rate (R) times the number of years that the back beach or bluff will be fixed (L) times the width of the property that will be protected (W). This can be expressed by the following equation:

Aw = R x L x W

Loss of material from natural back beach or bluff erosion.

Beach material comes to the shoreline from inland areas, carried by rivers and streams; from offshore deposits, carried by waves; and from coastal dunes and bluffs, becoming beach material when the bluffs or dunes lose material due to wave attack, landslides, surface erosion, gullying, etc. Coastal dunes are almost entirely beach sand and wind and wave action often provide an on-going mix and exchange of material between beaches and dunes. Many coastal bluffs are marine terraces — ancient beaches which formed when land and sea levels differed from current conditions. Since the marine terraces were once beaches, much of the material in the terraces is beach quality sand or cobble, and a valuable contribution to the littoral system when it is added to the beach. While beaches can become marine terraces over geologic time, the normal exchange of material between beaches and bluffs is for bluff erosion to provide beach material. When the back beach or bluff is protected by a shoreline protective device, the natural exchange of material either between the beach and dune or from the bluff to the beach will be interrupted and, if the shoreline is eroding, there will be a measurable loss of material to the beach. Since sand and larger grain material is the most important component of most beaches, only the sand portion of the bluff or dune material is quantified as beach material.

A seawall, gunnite facing, or revetment will prevent the material directly landward of it from eroding and becoming beach material. A seawall, gunnite facing or revetment will probably prevent some of the material above it from becoming beach material; however, some upper bluff retreat may continue unless the shoreline protective device extends the entire height of the bluff. Figure 4-4 shows several possible configurations of the bluff face, with a protective structure. The solid line shows the likely future bluff face location with shoreline protection and the dotted line shows the likely future bluff location without shoreline protection. The volume of total material which would have gone into the littoral system over the lifetime of the shoreline protective device would be the volume of material between the solid line and the dotted line, along the width of protected property. The actual erosion cannot be predicted, so the total erosion of the bluff must be approximated by the average annual long-term erosion of the bluff multiplied by the number of years that the structure will be in place. Finally, since the main concern is with the sand component of this material, the total material will be multiplied by the percentage of bluff material which is sand, giving the total amount of sand which would have been supplied to the littoral system if the proposed device were not installed.

Volume of sand denied the beach by the protective device (Vb) is equal to the percentage of sand in the bluff material (S) times the total width of the protected property (W) times the area between the solid and dotted lines in Figure 4-4 directly landward of the device[R x hs], plus the area between the solid and dotted area above the device [1/2hu x (R + (Rcu - Rcs))]. Since the dimensions and retreat rates are usually given in feet and volume of sand is usually given in cubic yards, the total volume of sand must be divided by 27 to provide this volume in cubic yards, rather than cubic feet. This can be expressed by the following equation:

Vb = (S x W x L) x [ (R x hs) + (1/2hu x ( R + (Rcu - Rcs)))]/27

In most cases, the quantified analysis of impacts to sand supply will stop with these calculations of lost beach area (the encroachment loss plus the long term loss of beach area with a fixed back beach) and the lost volume of beach sand. If there is an existing local or regional beach nourishment program in the area where the shoreline protective devices are being proposed, the areas of beach loss could be converted to the volume of sand needed to rebuild this same area of beach in the general area of the protective device. As mitigation for loss of beach area and beach sand, the analyst could prepare a condition which would require the applicant to contribute to the local or regional beach nourishment effort for a volume of sand equivalent to the volume of sand needed to rebuild the total amount of lost beach area plus the amount of material which would be kept from the littoral system.

To convert between area of beach and volume of sand to rebuild an area of beach, coastal engineers use a conversion value, v, which is in units of cubic yards per square foot of beach. The value is based on regional characteristics and is often assumed to be between 1 and 1.5, when there is not regional data to help quantify this value better. The value of v is based on the regional beach and nearshore profiles. To build a beach seaward one foot, there must be enough sand to provide a one foot wedge of sand through the entire region of onshore - offshore transport. If the range of reversible sediment movement is from -30 feet msl to +10 feet msl, then a one foot beach addition must be added for the full range from -30 to +10 feet, or 40 feet total. This 40 foot by 1 foot square parallelogram could be built with 1.5 cubic yards of sand (40 cubic feet divided by 27 cubic feet per cubic yard). If the range of reversible sediment transport is less than 40 feet, it will take less than 1.5 cubic yards of sand to rebuild one square foot of beach and if the range of reversible sediment transport is larger than 40 feet it will take more than 1.5 cubic yards of sand to rebuild one square foot of beach.

The volume of sand to rebuild the area of beach lost due to encroachment (Ve) is equal to the encroachment area (Ae) times the area to volume conversion (v). This can be expressed by the following equation:

Ve = Ae x v

The volume of sand to rebuild the area of beach lost due to long-term erosion (Vw) is equal to the area of beach lost due to long-term erosion (Aw) times the area to volume conversion (v). This can be expressed by the following equation:

Vw = Aw x v

Finally, if the condition will require that the applicant pay a fee for sand rather than provide the actual volume, the fee can be established as the total volume of sand (Ve + Vw + Vb) multiplied by the cost of transporting a cubic yard of sand (C) to the shoreline in the project vicinity.

C. Methodology Based on Science

The premise behind the sand mitigation program is that structural solutions to shoreline erosion, such as seawalls, revetments, cliff retaining walls, etc., alter natural shoreline processes. The shoreline processes which are affected by such shoreline protective devices include the formation and retention of sandy beaches and bluff retreat which adds bluff material to the shoreline. Shoreline armoring impedes these natural processes by fixing the back of the beach and preventing the landward migration of the beach profile, and by preventing bluff erosion from contributing to the sand supply.

Simply stated, the methodology which has been developed as part of the mitigation program is designed to calculate the beach area displaced and the amount of bluff material which does not reach the beach, as a result of a seawall; and to calculate the amount of sand which would be required to replace that lost beach area in the project vicinity. This amount of material is converted to a fee by multiplying the amount of material times the cost of transporting that material to the beach. The methodology quantifies some of the impact caused by the proposed armoring in terms of area of beach and volume of sand. To derive these amounts, the methodology utilizes the information specific to the proposed protective device, such as the design life, and to the project site, such as height of bluff, width of property, etc., and the predicted rate of erosion that was used to determine the need for protection of the existing structure.

The predicted rate of erosion is based upon historic trends and past shoreline responses. The erosion rate is predicted using the same methodology that is used to predict an erosion rate for purposes of concluding that an existing structure is threatened by erosion. Thus, the methodology uses site specific information and a scientifically sound prediction of erosion rates to quantify the amount of sand that will be lost as a result of the shoreline protective device. The fee is the money needed to buy an amount of sand equal to the sand lost as a result of the protective device. Since the amount of sand lost is quantified, the fee is directly related in extent to the impact of the project. Because the mitigation fee is used for beach replenishment in the same littoral cell where the impact occurs, the fee is also related to the type of impact of the project.

D. Application of Mitigation Program in San Diego County

As stated previously, the in-lieu fee has been required by the Coastal Commission through conditions of approval of coastal development permits for seawalls in the City of Encinitas and Solana Beach as mitigation for the impacts of the approved seawalls. This report is examining the use of a fee to be deposited in a mitigation fund in-lieu of placing sand on the beach to mitigate for the impacts of seawalls on natural shoreline processes in San Diego County. The shoreline in San Diego County is eroding. The concerns associated with the County’s eroding beaches have been addressed in the Shoreline Preservation Strategy adopted by the San Diego Association of Governments (SANDAG). The SANDAG Shoreline Erosion Committee has agreed to administer the fund and help identify beach replenishment projects which could be funded by the mitigation fees.

The Shoreline Erosion Committee of SANDAG is made up of representatives from each of the local coastal jurisdictions, the Port and the Navy with the representatives from the Coastal Commission, State Department of Boating and Waterways and the Department of Fish and Game serving as advisory members. One of the committee’s functions is to identify sources of beach quality material for purposes of replenishing the County’s eroding shoreline. Additionally, the committee is working on a Long Term Beach Replenishment Strategy. There are currently several sources of significant quantities of beach quality material identified, including the Navy Homeporting Project and the Sand for Trash project, which could augment the County’s beaches and provide an ongoing source for beach replenishment in the future. Also, there are opportunistic sources of beach sand reported at every committee meeting, many of which require funding to get the material transported to and deposited on the beach. It is these kinds of beach replenishment efforts which will be funded by the Beach Sand Mitigation Fund established through approvals of shoreline armoring in San Diego County. The Memorandum of Understanding approved by the Executive Director of the Coastal Commission and by the SANDAG Board establishing a process for the administration of the Beach Sand Mitigation Fund is attached as Attachment 2.

The situation is critical in San Diego and may be as critical in other areas along California’s coast. Because most of the County beaches are disappearing, there is no longer an adequate buffer between the waves and shorefront or blufftop development. As the buffer disappears, homeowners are likely to seek permission to build seawalls. If a fee to provide for beach replenishment is not pursued on a regional basis, this situation will likely result in an increased amount of shoreline armoring with no remaining sandy beach. This is why there is currently an increased amount of attention being focused on the need for beach replenishment in San Diego County by SANDAG and other Federal, State and local entities.

Therefore, in review of future proposals for shoreline armoring, the Commission staff in the San Diego District office will consider the site and project specific circumstances of each proposal for shoreline altering devices, determine what the impacts are and whether they can be quantified using the developed methodology. The staff will then consider whether payment of a fee in-lieu of placing sand on the beach is an appropriate mitigation for the long-term impacts to sand supply. Even when an impact is identified through application of the methodology, there may be other reasons why an in-lieu fee is not the best means to mitigate impacts to sand supply and/or access opportunities and other mitigation measures should be pursued. Additionally, there may be some instances when payment of a fee alone is not adequate mitigation and it should be coupled with additional measures, such as project redesign and/or a lateral access offer to dedicate, to address all the adverse impacts resulting from the proposed armoring. The analysts must use their judgment and project analyses to determine whether or not to recommend payment of the mitigation fee as a condition of approval.

The following are examples of several projects which have been reviewed by the Commission since the in-lieu fee beach sand mitigation fund was established, and were approved without a condition requiring payment of a mitigation fee. In one case, the staff did not recommend mitigation in the form of a in-lieu fee on a public seawall project in Carlsbad because adverse impacts to public access and recreational opportunities were being offset by project design, including public access improvements. In another case involving a private residential structure, the fee was not required and a lateral access dedication was determined to be sufficient mitigation. In that particular case, there was private sandy beach located seaward of the structure and the project was infill development. In a third case, the project was replacement of a previously approved seawall in La Jolla, where the original Commission approval did not require a mitigation fee; however, the project was required to be located as far inland as possible and a lateral access dedication was required as mitigation. And in a fourth case, the Commission required redesign from a revetment to a vertical seawall and the applicant was required to construct a public stairway providing vertical access as a condition of approval of the City-issued coastal development permit. Thus, staff determined adequate mitigation was being provided to offset the impacts of the seawall on public access. Also, because the bluffs are mostly rocky headlands, they do not make a significant contribution of beach material in the project location.

In summary, the proposed methodology uses the site specific conditions and the proposed project design as factors to determine some of the impacts to sand supply resulting from any proposal for a shoreline protective device. The impacts are quantified in terms of area of beach and volume of sand lost as a result of the seawall. The component of the methodology which addresses the contribution to sand supply from coastal bluffs would obviously not be applicable to armoring on beaches not backed by such bluffs; however, the impacts to sand supply resulting from direct beach encroachment and fixing the inland extent of the beach can still be determined.

The decision to convert the quantified impacts to a dollar amount, and require payment of a fee in-lieu of placing sand on the beach to mitigate the identified impacts, will be based on a variety of other factors, including but not limited to, the degree of impact; the availability of design modifications to eliminate or lessen the impact; whether or not actual beach replenishment could serve as mitigation; the availability of other forms of mitigation; the ownership of the beach and bluffs; and age and type of shoreline protection on surrounding properties. In some cases, it may be difficult to support payment of a fee in an area that has been historically armored and/or the bluffs have not contributed to sand supply for years. However, because the impacts to the long-term beach width are ongoing, it may be appropriate to quantify the impacts from fixing the back of the beach for the remaining life of the proposed structure. The appropriateness of the in-lieu fee as mitigation should be assessed on a project by project basis using past Commission action, consultation with staff legal counsel and the Procedural Guidance Document on Review of Permit Applications for Shoreline Protective Devices as guidance.

IV. RECOMMENDATIONS FOR USE OF THE MITIGATION PROGRAM IN OTHER LOCATIONS

As discussed in the preceding sections, the methodology utilized in the San Diego County Beach Sand Mitigation Program provides a means to quantify some of the impacts to sand supply caused by construction of shoreline protective devices. The methodology is also contained in the Procedural Guidance Document on Review of Permit Applications for Shoreline Protective Devices and can be used with any proposal involving a shoreline protective device as long as the information is available. Factors which will affect the degree of impact identified through the methodology include, but are not limited to, whether or not the project is proposed on an eroding shoreline; the availability of beach sand seaward of the protective device; the predicted erosion rate; and the percentage of sand in the bluff material. On beaches which are not backed by coastal bluffs, the impacts to sand supply resulting from direct beach encroachment and fixing the inland extent of the beach can still be determined. Impacts of shoreline protective devices located on wide, sandy beaches will be less; however, properties fronted by such beaches are also not likely to require a seawall to protect endangered development.

Recommendations

  1. When a shoreline protective device is required to protect existing structures in danger from erosion, assure mitigation for impacts to public beaches and long-term public recreational opportunity is adequately addressed.

The results of the ReCAP study showed that the Commission has not historically addressed the cumulative impacts of shoreline armoring in its review of coastal development permit applications for seawalls and revetments. The typical mitigation measure applied to seawall projects has been a condition of approval requiring the applicant to offer to dedicate a lateral access easement to cover the privately-owned sandy beach seaward of the approved protective device. This practice does not insure mitigation of impacts to sand supply and could result in significant cumulative and adverse effects on shoreline sand supply if adequate mitigation is not required with future armoring. The quantification of impacts discussed in this report can be used to support a variety of mitigation measures which will reduce or eliminate the effects of the project on shoreline sand supply.

  1. Utilize the Procedural Guidance Document on Review of Permit Applications for Shoreline Protective Devices to determine mitigation measures to address impacts on sand supply and public access.

The above referenced document contains an analytical process and sample conditions of approval which can be utilized by the permit analyst to develop the staff recommendation on projects involving shoreline protective devices. Examples of other forms of mitigation which can reduce or eliminate impacts to sand supply and access contained in that document include, but are not limited to, redesign from a revetment to a vertical seawall, relocation or realignment further inland, provision of lateral access in the design, offer to dedicate a lateral access easement seaward of the structure, deposition of beach material, and an in-lieu fee or user fee to compensate for encroachment on public beach. Support for alternative forms of mitigation can result from utilizing the methodology to quantify impacts and determine the significance of the impact and, thus, the appropriate mitigation.

  1. Work with Local Governments and Public Beach Property Owners to Develop Mitigation Programs Designed to Protect Public Beaches and Recreational Opportunity

The primary constraint to using the in-lieu fee as mitigation in locations other than San Diego County is the absence in other areas of an established program and a public entity, such as SANDAG, which has agreed to collect the fees and spend the funds on beach replenishment projects. However, when a shoreline protective device encroaches directly on State tidelands or publicly-owned beach, the permit analyst could coordinate with the public property owner, such as the local government, State Lands Commission or State Department of Parks and Recreation. The public agency, as property owner, may be interested in establishing a fund to compensate for the use of the public property and mitigate the impacts of the protective device on public beach. This idea has not been widely used in the past, but may be an appropriate response today given that some public beach areas are disappearing. The fee in this case could be a user or rental fee and should be roughly-proportional to the value of beach area lost as a result of the approved shoreline protective device. The fee should be used for projects within the same local or State jurisdiction or littoral cell, on projects involving public access improvements or for beach nourishment or maintenance. The methodology discussed in this report could be suggested as a means to quantify the amount of sand necessary to replace the beach area and bluff material lost as a result of the protective device and to derive an appropriate mitigation fee to offset the loss of public beach.

Another option would be for a local government to incorporate into their Local Coastal Program (LCP), measures to encourage beach replenishment and to mitigate the effects of armoring on sand supply. The LCP could contain a beach replenishment program which is financed, in part, by fees from property protection which encroaches on publicly-owned beach or otherwise adversely affects public beaches. The District staff should investigate the potential for working with local governments and State Parks to encourage those agencies to seek compensation for occupation of publicly-owned beach by seawalls. If the fees are then used for beach replenishment or access improvements, they are mitigation for impacts to public access and sand supply in accordance with Section 30235 and the public access and recreation policies of the Coastal Act.

V. REFERENCES

Everts, Craig, Memo by Dr. Everts dated 3/14/94 re: Review of Methodology for Quantifying Impacts to Sand Supply from Bluff Armoring

Kraus, Nicholas C. and Pilkey, Orrin H., "The Effects of Seawalls on the Beach", Journal of Coastal Research, Autumn, 1988

San Diego Association of Governments, Shoreline Preservation Strategy for the San Diego Region with Appendices, July, 1993


 

VI. ATTACHMENTS

IMPACT ANALYSIS FOR SHORELINE PROTECTIVE DEVICES

[Site Address]

Ve =

Volume of sand to rebuild the area of beach lost due to encroachment by the seawall; based on the seawall design and beach and nearshore profiles (cubic yards)

Ve = Ae x v

 

Ae =

The encroachment area which is equal to the width of the properties which are being protected (W) times the seaward encroachment of the protection (E)

 

Ae = W x E

 

W = Width of property to be armored (ft.)
E = Encroachment by seawall, measured from the toe of the bluff or back beach to the seaward limit of the protection (ft.)

v =

Volume of material required, per unit width of beach, to replace or reestablish one foot of beach seaward of the seawall; based on the vertical distance from the top of the beach berm to the seaward limit of reversible sediment movement (cubic yards/ft of width and ft. of retreat). The value of v is often taken to be 1 cubic yard per square foot of beach. If a vertical distance of 40 feet is used for the range of reversible sediment movement, v would have a value of 1.5 cubic yards/square foot (40 feet x 1 foot x 1 foot / 27 cubic feet per cubic yard). If the vertical distance for reversible sand movement is less than 40 feet, the value of v would be less than 1.5 cubic yards per square foot. The value of v will vary from one coastal region to another, but should not vary from lot to lot.[1]

Vw =

Volume of sand to rebuild the area of beach lost due to long-term erosion (Vw) of the beach and near-shore, resulting from stabilization of the bluff face and prevention of landward migration of the beach profile; based on the long-term regional bluff retreat rate, and beach and nearshore profiles (cubic yards).

Vw = Aw x v

 

Aw =

The area of beach lost due to long-term erosion is equal to the long-term average annual erosion rate (R) times the number of years that the back beach or bluff will be fixed (L) times the width of the property that will be protected (W) rate (ft./yr.).

 

Aw = R x L x W

 

R = The retreat rate which must be based on historic erosion, erosion trends, aerial photographs, land surveys, or other accepted techniques and documented by the applicant. The retreat rate should be the same as the predicted retreat rate used to estimate the need for shoreline armoring.

L = The length of time the back beach or bluff will be fixed or the design life of armoring without maintenance (yr.) For repair and maintenance projects, the design life should be an estimate of the additional length of time the proposed maintenance will allow the seawall to remain without further repair or replacement.

Vb =

Volume of sand denied the beach by the protective device is equal to the percentage of sand in the bluff material (S) times the total width of the protected property (W) times the years the structure will be in place (L) times the area between the solid and dotted lines in Figure 4-4 directly landward of the device[R x hs], plus the area between the solid and dotted area above the device [1/2hu x (R + (Rcu - Rcs))]. Since the dimensions and retreat rates are usually given in units of feet and volume of sand is usually given in cubic yards, the total volume of sand must be divided by 27 to provide this volume in cubic yards, rather than cubic feet. This can be expressed by the following equation:

Vb = (S x W x L) x [ (R x hs) + (1/2hu x ( R + (Rcu - Rcs)))]/27

S =

Fraction of beach quality material in the bluff material, based on analysis of bluff material to be provided by the applicant

hs =

Height of the seawall from the base to the top (ft)

hu =

Height of the unprotected upper bluff, from the top of the seawall to the crest of the bluff (ft)

Rcu =

Predicted rate of retreat of the crest of the bluff, during the period that the seawall would be in place, assuming no seawall were installed (ft/yr). This value can be assumed to be the same as R unless the applicant provides site specific geotechnical information supporting a different value.

Rcs =

Predicted rate of retreat of the crest of the bluff, during the period that the seawall would be in place, assuming the seawall has been installed (ft/yr). This value will be assumed to be zero unless the applicant provides site specific geotechnical information supporting a different value.

Vt =

Total volume of sand required to replace losses due to the structure, through reduction in material from the bluff, reduction in nearshore area and loss of available beach area (cubic yards). Derived from calculations provided above.

Vt = Vb + Vw + Ve

M= Vt x C

 

C =

Cost, per cubic yard of sand, of purchasing and transporting beach quality material to the project vicinity ($ per cubic yard). Derived from the average of three written estimates from sand supply companies within the project vicinity that would be capable of transporting beach quality material to the subject beach, and placing it on the beach or in the near shore area.


ATTACHMENT 2

 

Memorandum of Agreement Between the San Diego Association of Governments (SANDAG) and the California Coastal Commission (herein referred to as the Commission)
Establishing a Process for the Administration of the
Beach Sand Mitigation Fund

WHEREAS, the Beach Sand Mitigation Fund consists of fees collected by the California Coastal Commission through its coastal development permit process pursuant to special conditions of various permits, as mitigation for the adverse impacts of shoreline protective structures, such as seawalls and revetments, on the beaches within San Diego County;

WHEREAS, the mitigation fees are deposited in an interest bearing account created at SANDAG, with all interest earned payable to the account for purposes stated below;

WHEREAS, the purpose of the account is to establish a beach sand mitigation fund to aid local governments, working cooperatively through SANDAG, in the restoration of the beaches within San Diego County;

WHEREAS, the funds shall be solely used to implement projects which provide sand to the region’s beaches, not to fund operation, research, maintenance or planning studies;

WHEREAS, the funds shall be allocated as provided for in this memorandum of agreement (MOA) between SANDAG and the Commission, setting forth terms and conditions to assure that the mitigation fees will be expended in the manner intended by the Commission; NOW, THEREFORE

BE IT RESOLVED that it is the intent of the Coastal Commission and SANDAG to participate in the administration of the Beach Sand Mitigation Fund as follows:

1. Fund Administration

The Commission and SANDAG agree, that the mitigation fees will be held by SANDAG in a trust fund maintained and operated by SANDAG as one fund; however, SANDAG agrees to establish a separate accounting for monies within the fund for each coastal jurisdiction in the San Diego region. Mitigation fees from approved shoreline protection projects within each coastal jurisdiction shall be accounted for by jurisdiction;

Money from a coastal jurisdiction’s account cannot be spent without that jurisdiction’s formal approval through resolution by City Council or Board of Supervisors;

The money in the fund will be invested by SANDAG in accordance with applicable law. Income and/or interest will be credited to each coastal jurisdiction’s account on a pro-rated basis. A copy of the annual accounting review shall be submitted, upon completion, to the Executive Director of the Commission.

2. Fund Allocation

The Commission and SANDAG agree, that the region’s coastal jurisdictions, working together through the Shoreline Erosion Committee, will evaluate proposed beach replenishment projects, and determine how much, if any, money from the fund should be allocated to a project, and how much of the total allocation should come from each jurisdiction’s account. No funds shall be allocated from a jurisdiction’s account without that jurisdiction’s formal approval through resolution by City Council or Board of Supervisors;

The Commission and SANDAG agree that, prior to allocation of any funds, the recommendation of the Shoreline Erosion Committee, after adoption by SANDAG, must be submitted to the Executive Director of the Commission for review and approval. The Executive Director must provide written concurrence with each allocation, before any allocation occurs;

The Commission and SANDAG agree that each disbursement will be made to the recipient with conditions that guarantee that the fees are used as intended by the Shoreline Erosion Committee, SANDAG and the Executive Director. Any unused funds shall be returned to the contributing coastal jurisdictions’ account(s) on a pro-rated basis.

3. Eligible Projects

Only projects which meet all of the following will be considered by the Shoreline Erosion Committee and SANDAG for funding:

a. Only projects that are recommended to the Shoreline Erosion Committee after formal action by a local coastal jurisdiction will be considered for funding. Projects may be carried out by the local jurisdictions themselves; by other agencies, including, but not limited to, the Corps of Engineers, the U.S. Navy, the California Coastal Conservancy or the State Department of Boating and Waterways; or by private parties and/or non-profit organizations;

b. Only projects that involve sand replenishment for beaches in San Diego County will be considered for funding. Since the fees that will go into the fund are intended to mitigate adverse impacts of shoreline protective structures on beach sand supply, only projects that add sand to the region’s beaches shall be supported by the fund; and

c. Only capital projects will be considered for funding. Mitigation fees cannot be used for operations, research, maintenance or planning studies. The Committee may recommend that funds should be allocated to engineering or permitting (e.g. environmental documentation) costs directly related to the implementation of a capital project, under extraordinary circumstances only.

Sand projects like those listed in the "Update on Opportunistic Sand Projects" which appear on the Shoreline Erosion Committee’s agenda each meeting may be considered for funding. These projects typically have sand available but require additional funds to move the sand to the beach;

Any project considered for funding must obtain a coastal development permit, waiver or exemption from the local government having jurisdiction, or the Commission, prior to initiation of construction.

4. Project Funding Criteria

The Commission and SANDAG agree the objectives, policies and recommendations contained in the Shoreline Preservation Strategy dated July 1993, and the guiding principles adopted in 1995 by the Shoreline Erosion Committee, should be used by the coastal jurisdictions in deciding how to allocate the fund to projects. SANDAG staff will provide an evaluation of how a particular project meets these criteria. The Shoreline Erosion Committee shall use this evaluation as a basis for their discussions and decisions on funding allocation.

The Commission and SANDAG agree that funds generated within a coastal jurisdiction from a specific littoral cell shall be used only for projects affecting that same littoral cell.

BE IT FURTHER RESOLVED that it is the intent of this Memorandum of Agreement to assure consistency in the administration and allocation of mitigation fees from the Beach Sand Mitigation Fund.

BE IT FURTHER RESOLVED that this Memorandum of Agreement may be altered, changed or amended by mutual consent of the parties hereto. Either party may terminate this MOA by providing written notification 30 days prior to termination.

BE IT FURTHER RESOLVED that in the event of termination of this Memorandum of Agreement by either party, any and all remaining funds shall be transferred by SANDAG to the Commission or a Commission-approved alternate entity.

SAN DIEGO ASSOCIATION OF GOVERNMENT

 

CALIFORNIA COASTAL COMMISSION

_______________________________________   _______________________________________

Executive Director

 

Executive Director

_______________________________________   _______________________________________

Date

 

Date


ATTACHMENT 3

 

Beach Sand Mitigation Fund

Applicant's Name

Address

Mitigation Fee Total

Amount Paid

Amount Due

Permit Number

Date Next Payment

   

$

$

$

   

Evleth

312 Neptune, Encinitas

$2,918

$2,918

$-

6-93-85

 

Pierce

370 Neptune, Encinitas

2,876

2,876

-

6-93-85

 

Rose

378 Neptune, Encinitas

3,004

360

2,644

6-93-85

9/1/1996

Auerbach

396 Neptune, Encinitas

2,982

2,982

-

6-93-85

 

Frickman

402 Neptune, Encinitas

3,004

3,004

-

6-93-85

 

Milis (Farmer)

470 Neptune, Encinitas

5,406

5,406

-

6-93-131

 

Knotts

478 Neptune, Encinitas

3,862

3,862

-

6-93-131

 

Harlow

492 Neptune, Encinitas

6,178

6,178

-

6-93-131

 

Oakley

498 Neptune, Encinitas

3,089

3,089

-

6-93-131

 

Klinck

502 Neptune, Encinitas

3,089

3,089

-

6-93-131

 

Sbordone

510 Neptune, Encinitas

3,089

3,089

-

6-93-131

 

Sbordone

518 Neptune, Encinitas

4,634

4,634

-

6-93-131

 

Richards(Barshick)

522 Neptune, Encinitas

7,990

7,990

-

6-93-131

 

Favero

452 Neptune, Encinitas

7,776

7,776

-

6-93-136

 

Hann

386 Neptune, Encinitas

3,069

3,069

-

6-95-66

 

Coleman

680 Neptune, Encinitas

4,051

4,051

-

6-90-100

 

Clayton

638 Neptune, Encinitas

4,881

4,881

-

6-93-36-G

 

Wood

521 Pacific, Solana Bch

5,770

5,770

-

6-92-212

 
 

TOTAL

$77,666

$75,023

$2,644

   
             

City of Encinitas *

N. El Portal (Low Est.)

$2,000

$-

$2,000

6-94-88

Jan-95

City of Encinitas *

N. El Portal (High Est.)

$10,979

$-

$10,979

6-94-88

Jan-95

             

*The City of Encinitas has not yet submitted figures to calculate the exact mitigation fee due. Thus, they have not been included.


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