How can cliffs be protected from erosion

This results in the highest level of reliability and confidence that you as our valued client expect and deserve. Coastal erosion occurs when the waves that lap at the coast slowly wear away at the shoreline. As these waves wash over the shore, they carry sand and sediment with them and redistribute it to the ocean floor or to other areas.

Erosion can be worsened by factors such as high winds, wave currents, and tidal currents. Because all of these conditions are common in Florida, beach erosion is a common occurrence in the state. That is why finding ways to stop coastal erosion is even more important to residents of Florida than those of other states. If you live in Florida, you have likely seen the damage that can result from beach erosion.

The process of erosion slowly eats away at the coastline. If the structure itself fails, particularly early during the storm event, then the bank will fail and infrastructure may be threatened or damaged Figure For example, if a property owner wants to protect the shoreline from high water for 10 years, the designer might choose a year design wave condition see Table ; Figure In most cases, the project life is designed for 25 years year design condition , with a 64 percent chance of failure during that time interval.

The following hypothetical example is offered to illustrate how site conditions affect the range of effective erosion control options available to the homeowner. Top of structure is at 2 meters approx. Note significant bank scarping due to Hurricane Isabel when the combination of storm surge and wave runup reached 4 meters approx.

The structure and upper bank face are still intact. A homeowner lives on a ft waterfront parcel on a tidal creek. The shorefront consists of a narrow beach backed by a ft high eroding bank. No buildings are immediately threatened but with every northeaster the homeowner loses about a foot of land. The neighbor on the right Neighbor R , south and downstream of the homeowner, has a wood bulkhead and graded bank.

The neighbor on the north side Neighbor L has a similar shorefront as the homeowner, but with less erosion on the upstream side where the bank is fronted by a marsh fringe see Figure The homeowner decides to investigate options for stemming the erosion of her property and hires a consultant. The consultant analyzes the site conditions and offers the 4 options described below.

The shoreline is on a slight headland that is exposed to the northeast. To the north and southeast, the fetch is less than a mile, but the northeast opens to a sound, about 3. There is a 2-ft tidal range and storm surges of 2 ft or more above normal can be expected every 3 to 5 years. Larger, less frequent storms will cause storm surges of over 5 feet. Bank erosion is associated with storms and associated high water and wave action. Neighbor L has a similar problem that becomes less severe toward the north because the property is more sheltered from the northeast exposure.

The bank face on the opposite side of the lot is fairly stable with heavy vegetation but a significant wave-cut scarp along the base. The marsh fringe on. However, boat-wake impacts may increase as development continues along the creek, causing more erosive damage to the marsh fringe.

Option 1—take no action. Since the house is 75 ft from the bank, infrastructure will not be at risk for many years given an average erosion rate of less than one ft per year.

Loss of property and landscaping notably trees will continue. This will have no direct costs for the homeowner. Option 2a—create marsh fringe vegetation. There are many places along the upper reaches of the creek where just trimming trees and planting the existing substrate could significantly enhance a protective marsh fringe.

In addition, the marsh fringe will require ongoing maintenance. Cost to the homeowner is low, but there will be ongoing maintenance costs. Option 2b—create marsh fringe vegetation with sill. To protect the new marsh from wave exposure a sill will be installed to attenuate wave action. The sill, typically composed of rocks, will run parallel to the shore at a distance to match the desired width of the created marsh.

Sandy fill will be placed behind. T is the return period of a particular extreme wave condition in years. P is the probability of a particular extreme wave condition occurring during design life N years.

The sand fill level will be about 3 ft above MHW at the base of the graded bank. The sand fill will be graded to form a slope to intersect the back of the sill at about mean tide level MTL. This is about the lower limit of tidal marsh. The sill will be about 40 ft creekward of the base of the graded bank. Some of the original marsh will be affected, but the new marsh fringe should compensate for the loss.

Some of the sandy graded bank material will be used for the wetlands terrace but any excess will be hauled offsite. There may be some maintenance required after storm events, especially in the first few years until the marsh becomes established. Native shrubs will be planted on the bank face to create a riparian buffer and minimize the need to fertilize compared to grass , reducing the nutrient input into the creek and state waters.

This option is very expensive for the homeowner who must cover costs of construction, maintenance, and obtaining a permit to place a sill on state-owned creek bottom.

Obtaining a permit may be difficult because of multiple levels or regulatory review. Also, this option will require the cooperation of neighbor L, but it preserves the visual landscape which is a high priority for both neighbor L and the homeowner. Option 3—extend the bulkhead. The life expectancy of the bulkhead should be at least 20 years, possibly more depending on the durability of the bulkhead material.

There is evidence of bank scarping by wave action, but the integrity of the bank slope is intact and is repaired with some minor fill and vegetation. Cost to the homeowner is moderate, no federal permit will be required, and this option is preferable to neighbor R.

The project design life of the bulkhead should be at least 20 years, possibly more depending on the durability of the bulkhead material. Option 4—install a stone revetment. The bank would be graded by cutting the top back and pushing it creekward to create a subgrade. The minimum required bank slope is , but lesser slopes, say , would provide more effective wave attenuation during large storms and reduce bank scarping. Here the revetment would continue along a new subgrade in front of the stable bank face.

Some of the existing marsh would be covered by the structure, potentially requiring some form of compensation for loss of wetland. Cost to the homeowner is moderate to high. Although construction will require a permit, the permitting should be straightforward and unlikely to cause a major delay in the project. The project design life of the rock is 50 years or more and the integrity of the structure depends on quality construction.

In addition to showing how the site conditions affect the suitability of erosion control measures, this hypothetical case indicates some of the choices that face a homeowner with regard to cost, permitting, and potential changes to the landscape. The decision-making context for addressing erosion is further explored in Chapter 5.

Strategies that address erosion, other than land use controls, can have cumulative impacts to sheltered coasts. These include permanent removal of sand from the littoral system, creating oversteepened shore faces, loss of intertidal zones, and habitat loss.

Managing land use has long-term individual and cumulative benefits that extend beyond those produced by other types of erosion control.

These elements may have differing priorities for a given project but all are relevant to achieving optimum costs and benefits. Matching any of the many approaches to the appropriate setting then becomes the fundamental challenge. Many engineers, contractors, and property owners are unaware of the range of options available for controlling erosion. Like ocean beaches, sheltered coastal areas experience land loss from erosion and sea level rise.

In response, property owners often install hard structures such as bulkheads as a way to prevent further erosion, but these structures cause changes in the coastal environment that alter landscapes, reduce public access and recreational opportunities, diminish natural habitats, and harm species that depend on these habitats for shelter and food. Mitigating Shore Erosion Along Sheltered Coasts recommends coastal planning efforts and permitting policies to encourage landowners to use erosion control alternatives that help retain the natural features of coastal shorelines.

Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website. Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book. Switch between the Original Pages , where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

To search the entire text of this book, type in your search term here and press Enter. Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available. Do you enjoy reading reports from the Academies online for free? Sign up for email notifications and we'll let you know about new publications in your areas of interest when they're released.

Get This Book. Visit NAP. Looking for other ways to read this? No thanks. Suggested Citation: "3 Methods for Addressing Erosion. Page 45 Share Cite. Manage Land Use. Page 46 Share Cite. Page 47 Share Cite. Page 48 Share Cite. Page 49 Share Cite. Courtesy of VIMS. Page 50 Share Cite. Page 51 Share Cite. Page 52 Share Cite. Page 53 Share Cite. Courtesy of the New York Sea Grant. Page 54 Share Cite. Page 55 Share Cite. Page 56 Share Cite. Page 57 Share Cite. Page 58 Share Cite. Page 59 Share Cite.

Page 60 Share Cite. Page 61 Share Cite. Page 62 Share Cite. Page 63 Share Cite. Page 64 Share Cite. Page 65 Share Cite. Page 66 Share Cite. Headland Control. Nontraditional and Innovative Methods. Page 67 Share Cite. Page 68 Share Cite. Level of Protection. Page 69 Share Cite. Damage and Risk Assessment. Page 70 Share Cite. Page 71 Share Cite. The global rise in sea level, combined with the increased and often poorly planned development of erosion-prone ocean-front land, and a number of recent damaging hurricanes, has Skip to main content Skip to table of contents.

This service is more advanced with JavaScript available. Environmental Geology Edition. Contents Search. Coastal erosion and protection. Authors Authors and affiliations Gary B. How to cite. This is a preview of subscription content, log in to check access.