Community Conversations

Coastal Erosion in a Changing Climate

Prepared for the Pratt Museum by Dr. Deland S. Anderson
In Conjunction with the Community Conversation of April 17 2008

Wherever the settlement of Homer has pushed up against the ocean bluff, erosion is a chronic problem to property owners. Naturally some properties, because of their location in the topography are more exposed than others, and consequently undergo more erosion and suffer more damage than their neighbors. Naturally, too, in a volatile and dynamic coastal zone as we have here, the topography shifts—sometimes gradual and sometimes cataclysmic—and so points of greater exposure shift from one property to another. Furthermore, when one property owner takes measures to mitigate erosion of his/her property, it sometimes results in making the problem worse for neighbors.

The settlement of Homer meanders along the shore of Kachemak Bay for approximately 20 miles (from Bluff Point to Miller's Landing, including the length of the Spit). This is but a fragment of a distinct type of coastline that stretches from Knik Arm north of Anchorage all the way to the head of Kachemak Bay. A visit to any segment of this coastline in Cook Inlet (with the exception of Turnagain Arm, which is of a different type, will reveal evidence of massive and long-term erosion. If one takes the long view, one sees ample evidence everywhere of glaciation and tectonic upthrusts or subsidence that have worked truly remarkable changes upon the landforms. In the near term, one finds superimposed upon that canvas more recent changes, such as might be caused by a heavy rain or big storms. Repeat visits to the same areas over the course of years will show how dramatic and swift this erosion can be. Huge boulders will tumble out of the bluff, land on the beach, and be covered and uncovered in succession as loads of sand and gravel and silt migrate along the strand. The forces of wind-born waves, tides, and ice pack provide the energy for such beach sculpting. Changing groundwater tables, migrating springs, freeze and thaw cycles, wind, earthquakes, and plain old gravity also reshape the overhanging bluffs.

In the Homer region, more than 200 feet of bluff have disappeared into the ocean in certain areas since the 1964 earthquake. Homes and other developments are not uniformly scattered throughout this zone, and so not all have been impacted by the receding bluff or subsidence. But an interesting coincidence can be noted—where there is denser settlement, there are more extreme erosion problems. One is led to wonder whether this is the case just because erosion is both more apparent and better documented in more heavily populated areas or alternatively because the development itself exacerbates an ongoing process of coastal erosion. (It is somewhat repugnant to believe—as some clearly do—that certain people just flock to unstable bluffs and build there.) Particular zones within this stretch of beach have undergone rip-rapping and other processes to slow the effects of erosion. Some attempts have been more successful than others, but most are in a constant state of failure. The following is a miscellany of efforts. Army Corps of Engineers’ rip-rapping of the Homer Spit at the cost of many millions of dollars still allows significant erosion of the roadbed. A boardwalk, built on pilings high above the gravel strand, was swept off the Spit late this winter near Eco Beach. The Fishing Hole (a man-made lagoon on the inside of the Spit) is repaired intermittently due to damage caused by fall storms. This is true as well for the barge basin just to the northwest. The walking path that lines the Spit on the inside has had to be repaired more than once due to the asphalt surface being undermined by storm waves. In other areas, where the beach is topped by bluffs ranging from over a thousand feet high to a mere six feet high, numerous houses have been moved or have been lost over the bluff due to sudden and significant events. At the bottom of West Hill Road a large section of the beach bluff sloughed off and plummeted more than a hundred feet to the beach below, taking with it the front deck of local resident Joe Lawlor. Houses just East of Bidarka Creek have been moved back because the soft clay bluff is slumping into the bay. The peat-packed section of bluff along Ocean Drive at the base of the Spit has receded rapidly in recent years, taking at least one building with it. A much-contested seawall has been erected to mitigate the erosion, but it has failed on more than one occasion, and has required reconstruction. The mouth of Beluga Slough has been dredged and redirected a number of times in recent years in order to lessen erosion of properties on Munson Point. The section of beach from Mud Bay to Miller's Landing has undergone significant erosion, resulting in the loss of real estate and some improvements. Homeowners along this stretch make due as best they can with homemade remedies. Several of them attended the Pratt Museum’s Community Conversation on Coastal Erosion in a Changing Climate

A lively and well-informed group of local residents gathered amidst the museum’s provocative Concerning Climate Change art exhibit to express frustration, fear of erosion, loss of property, as well as to share valuable baseline data and techniques for erosion mitigation. One resident provided numerous photographs documenting changes in recent years to the section of bluff that stretches from the Spit to Miller's Landing. Special focus was placed on erosion and flooding to this area that resulted after changes made to Kachemak Drive a couple of years ago. Last February brought significant flooding and erosion following an unusual winter rainstorm.

Participants discussed an array of techniques, technologies, and trademarks. Culverts, sump pumps, landscaping fabrics, rip rap, seawalls, and log berms were assessed for their merits in dealing with too much water—whether from the ocean, the sky, the ground, or the City of Homer waterline extension. Slope angle, slope toe, and ground cover were also discussed. After a great deal of analysis, a good deal of finger-pointing, a modicum of optimistic planning, one participant, rather caustically it seems, asked—What are you going to do besides just sit back and watch it slide into the bay?

This remark seems to be based on the sentiment alluded to above—some people are fools, and some of those fools build on the bluff. But this sort of finger pointing is disingenuous in a town like Homer. Consider that those of us who do not live on the beach bluff likely live on steep slopes, along creeks, in the bottoms of canyons, or in wetlands. Indeed, as one old timer stated with regard to Homer, it’s all on the move. True, there are a few fortunate or wise residents who enjoy raised, gently sloped, home sites atop firm and dry soils. But they are rare exceptions in this area. And they are not above criticism, as these sites are all several miles uphill from the town center and it’s in the commute where the problem lies, as will become apparent in the sequel.

The facilitator encouraged the group to consider how local causes contribute to global climate change, and how, in turn, global climate changes might be contributing to local erosion problems. Here is one example of how the complex loop might be completed. Longer commutes generally result in more automobile emissions. Automobile emissions are a major contributor to greenhouse gas increases. Increases in greenhouse gases have led to a warming trend in the earth’s atmosphere. This, in turn, has led to more extreme storms. Such massive storms in the Pacific have impacted Alaska with torrential rains, hurricane-force winds, storm surge, and above average surf. This has led to direct and obvious erosion to our beach bluff.

One participant offered another way to complete the loop. Logging operations in Kachemak Bay have released sequestered CO2 into the atmosphere. This increase in CO2 in the atmosphere contributes to global warming. Global warming has resulted in local climate change, including warmer summers in Southcentral Alaska. These warmer summers enabled the spruce bark beetle to achieve epidemic populations on the Kenai Peninsula. The epidemic effectively killed off millions of acres of spruce in the region, including almost every mature tree in Homer. The loss of this forest has resulted in increased bluff erosion due to increases in the water table, more rapid surface water runoff, and the release of soils formerly held in place by the spruces’ root masses.

Numerous other connections were considered. Global warming may be responsible for numerous factors that ultimately affect the erosion rate of our beach bluff. Warmer winters lead to more runoff; when precipitation falls as snow it is ultimately less erosive than when it falls as rain. (The effects of heavy rain storms in winter when the ground is frozen was noted above.) Warm winters can be ominous in this area. One participant mentioned a sort of prayer offered by some bluff residents—Please, just freeze! This is because frozen ground is less liable to erosion than is sodden ground. Additionally, more violent storms associated with global warming lead to a more extreme sea state (the height and frequency of waves), and Homer’s beach lies at the receiving end of the longest fetch for waves in the world! One participant noted the effect of wind-born waves on the bluff at Miller’s Landing. Winds funneling down off Grewingk Glacier across the bay to the East drive waves straight into Miller’s Landing on the Western shore. Any increase in the severity of these winds will result in more destructive waves. An unusual phenomenon mentioned by another participant may be the result of huge storms, vast fetch for waves to build, and the narrow opening of the mouth of Cook Inlet. Last winter, residents of Nanwalek, on the south shore of Kachemak Bay, witnessed a tide that went out when it was supposed to be coming in. For this community, that has witnessed tsunamis in living memory, this was an ominous sign. As it turned out, it was not a tsumani wave, but a seiche. A seiche (pronounced saysh) is like the water that sloshes in the bathtub. A storm generates a surge that pushes a wall of water toward the edges of a body of water, often in one direction. The storm surge pushes unusually far onto the beach, then recedes, creating the appearance of an outgoing tide. This sloshing motion can be repeated several times before the seiche dissipates. Just as with a tsunami, if the occurrence of a seiche is timed with a large tide, significant erosion would be the likely result. Note, too, that global warming is creating not just larger storms but more frequent large storms. The erosive effects on the coastline are increased with greater rainfall, increased with greater storm surge, increased with greater surf action, increased with greater siltation. There is even a little loop here. The more heavy rain in this area, the more runoff we have. The more runoff, the more siltation we have in the creeks and the bay. The more siltation there is, the more powerful the effects of the water—water moves faster and hits harder when it is silt-laden. And what this fast-moving, hard-hitting water does best is create more siltation through erosion. Participants discussed ice as well. Ice dams culverts, causing overflow to erode around and beneath the culvert. Photographs were shown to demonstrate this in one instance along Kachemak Drive. Ice lenses were also discussed. These are pockets of ice trapped in the ground between layers of soil. When they melt, the soils fail, and increased erosion results. Finally, sea ice came into play. One of the old timers offered that in 1947 Kachemak Bay had frozen all the way from Homer to Seldovia. But this is memorable only because it is exceptional. Kachemak Bay is generally ice-free throughout the winter. Yet it does produce significant pancake and shore ice most years. And such ice significantly reduces wave action on the beach and at the foot of the bluff. One could speculate, then, that if a warming climate has led to less ice in the bay, it has likely increased the rate of erosion.

To bring the conversation full circle, the facilitator prompted the group to again consider the obvious local causes of erosion. Given the effects of global warming and climate change mentioned above, we may reasonably expect that the rate and extent of coastal erosion will increase. Numerous cases around the world indicate as much. Certainly the woes of Kivilina and Shishmaref, among other coastal Alaskan communities, provide a close corollary to Homer. While Homer will not be relocated root and branch as these villages undoubtedly will, still there is enough former real estate that is now underwater in this area for us to heed the warning of our more northern brothers and sisters. In any case, increasing erosion demands better planning, mitigation, and stewardship. Clearly some practices are more effective and desirable than others are. As a community, there is a need to establish what measures are acceptable. Should there be a moratorium on all new development on the bluff? The City of Homer is presently drafting a steep slope ordinance, which may or may not impact bluff development. Should there be a mandate for cooperative efforts, as with the seawall along Ocean Drive, so one neighbor’s good intentions do not adversely affect another’s property? Should the City of Homer recognize that the entire settlement it anchors contributes in multifarious ways to the problem of erosion, whether through hard surface development and the associated runoff, or through the eradication of trees in rights of way? Finally should we take this crisis as an opportunity to reflect on the wisdom of our daily practices, the vision of our future, and the plight of others in similar situations around the world? Manifestly so.