Incision Patterns Research Articles

Climate and local geomorphic interactions drive patterns of riparian forest decline along a Mediterranean Basin river

Dynamic fluvial processes strongly influence ecological communities and ecosystem health in riverine and riparian ecosystems, particularly in drought-prone regions. In these systems, there is a need to develop tools to measure impacts from local and regional hydrogeomorphic changes on the key biological and physical processes that sustain riparian ecosystem health and potential recovery. We used dendrochronology of Populus nigra, a riparian tree that is vulnerable to changes in local hydrology, to analyze ecosystem response following channel incision due to gravel mining along the Drôme River, a Mediterranean Basin stream in southern France. We cored 55 trees at seven floodplain sites, measured ring widths, and calculated basal area growth to compare the severity and timing of local growth decline along the river. Current basal area increment (BAI) growth per tree ranged almost 10-fold among sites (7.7±1.3 to 63.9±15.2cm2year−1, mean±SE) and these differences were significant. Mean BAI was correlated positively with the proportion of healthy trees at a site, and negatively with proportion of dead canopy area. Regime shift analysis of the tree-ring series indicates that tree growth declined significantly at four sites since 1978, coincident with documented channel incision. In addition, patterns of low growth and crown dieback are consistent with stress due to reduced water supply. The most impaired sites were not directly adjacent to local mining pits visible on aerial photographs, nor did the sequence of growth regime shifts suggest a pattern of channel incision progressing from these areas. The initiation of site growth declines was most typically associated with drought years, and the most impaired sites were spatially distributed to suggest the influence of local bedrock controls on soil depth. Climate in the Drôme basin and in the Mediterranean region is trending significantly toward hotter growing seasons with a decrease in summer river discharge, and this will increase both chronic and acute water shortage for riparian trees. This study shows that drought-prone riparian forests are vulnerable to hydrogeomorphological changes, but the severity of impacts is conditioned by interactions between drivers at different scales, including regional climate variability, reach-based geomorphic alteration, and local lithological controls.

The effects of precipitation gradients on river profile evolution on the Big Island of Hawai'i

To better understand how climate affects bedrock river incision and long-term landscape evolution in the absence of tectonic forcing, we quantify differences in the longitudinal profiles of eroding bedrock channels across the Kohala peninsula on the northern tip of the Big Island of Hawai’i. An orographic rainfall gradient causes mean annual precipitation rates to vary by over an order of magnitude, from greater than 4000 mm/yr on the wet side to less than 250 mm/yr on the dry side of the peninsula. Channels on the wet side are relatively deeply incised into the surrounding landscape and have developed profiles in which slope increases downstream in upstream reaches (convex form) and decreases downstream in downstream reaches (concave form). Wet-side river channels have relatively large (10–30 m) vertical steps, or knickpoints, in the convex zone. In contrast, channels on the dry side of the peninsula are more shallowly incised, have developed nearly straight longitudinal profiles in which channel slope does not significantly change from upstream to downstream, and have smaller knickpoints. Channel profile form changes from straight to convex-concave at a watershed-averaged mean annual precipitation rate of between ∼1300 and 1750 mm/yr, suggesting a climatic threshold in this landscape, above which bedrock incision rates are enhanced. Valley depth (used as a proxy for the magnitude of channel incision) increases with increasing mean annual precipitation and is consistent with a similar fluvial-incision threshold. While the lithology is entirely basalt, incision patterns also appear to be affected by spatial differences in bedrock weathering due to both local climate and basalt flow age. The older and more weathered Pololū basalts (260–450 ka) are capped by the younger Hawī basalt series (120–260 ka), and we interpret that heterogeneous weathering of these units influences channel form, relief, sediment production, and knickpoint development.

Precise Identification of Filtration Openings on the Scleral Flap by Three-Dimensional Anterior Segment Optical Coherence Tomography

To elucidate the potential of three-dimensional anterior segment optical coherence tomography (3D AS-OCT) for identifying filtration openings where aqueous humor flows from the sclera into the subconjunctival space. We used 3D AS-OCT and custom software to identify filtration openings, which were defined by pits and/or troughs in fluid-filled cavities in both horizontal and vertical rasters and corresponding C-scan images of scleral flap margin in the blebs. We measured bleb parameters, and at least three different reviewers surveyed the complete 3D images of the internal structure of the filtration blebs and associated findings. We identified filtration openings in 118 (95%) of 124 eyes. Among these 118 eyes, we found only a single filtration opening in 90 eyes (76%) and two or more filtration openings in the remaining 28 eyes (24%). Filtration openings were located in the middle third of the scleral flap margins in 57 eyes (63%) of the 90 eyes. The pattern of incision and sutures used for closure of the conjunctival flap affected the location of the openings, but additional laser suture lysis did not. In 6 (5%) of the 124 eyes, filtration openings could not be identified because of high reflectivity and/or elevated bleb wall (2 eyes), and no fluid-filled cavities because a sponge-like structure masked the filtration openings just above the scleral flap (4 eyes). 3D AS-OCT allows, in most cases, detailed evaluation of internal morphology of filtration blebs and precise identification of filtration openings on the scleral flap margins after trabeculectomy.

Abrupt landscape change post–6 Ma on the central Great Plains, USA

The principal control on landscape evolution in the central Great Plains of the United States over the past 10 m.y. is a contentious subject. New sedimentary data collected from Late Miocene Ogallala Group and Pliocene Broadwater Formation of the Nebraskan Great Plains demonstrates a twofold increase in the median grain size (from 20 mm to >40 mm) exported from the Rocky Mountains across the Miocene-Pliocene boundary. Paleoslope reconstructions derived from these data support the tilting of the Miocene Ogallala Group after 6 Ma, but demonstrate that the transport slope of the lower part of the unconformably overlying Pliocene succession is identical to the present-day slope. These data allow us to constrain the timing of differential uplift in the Great Plains to between 6 and 3.7 m.y.; the wavelength and short duration of this tilting are best explained by the initiation of localized dynamic topography. Our results also suggest a threefold to fourfold increase in specific stream power at this time, meaning that Pliocene rivers draining the central Rockies were considerably more competent than their Miocene predecessors. Incision during this period was not continuous. A significant episode of aggradation from 3.7 to 2.5 Ma is best explained by high rates of sediment supply relating to the warm, wet mid-Pliocene climate optimum. The modern pattern of incision on the Great Plains occurred from 2.5 Ma, and not from the end of the Miocene as is sometimes supposed, reflecting the onset of major Northern Hemisphere glaciation.

Interaction between the controls on fluvial system development: tectonics, climate, base level and river capture – Rio Alias, Southeast Spain

ABSTRACTFluvial systems in uplifting terrain respond to tectonic, climatic, eustatic and local base‐level controls modified by specific local factors, such as river capture. The Rio Alias in southeast Spain is an ephemeral, transverse‐to‐structure fluvial system. The river drains two interconnected Neogene sedimentary basins, the Sorbas and Almeria basins, and crosses two major geological structures, the Sierras de Alhamilla/Cabrera and the Carboneras Fault Zone. Regional epeirogenic uplift resulted in sustained fluvial incision during the Quaternary, punctuated by major climatically driven periods of aggradation and dissection, which created a suite of five river terraces. The river terrace sequence was radically modified in the late Pleistocene by a major river capture (itself a response to regional tectonics), localized tectonic activity and eustatic base‐level change. The Rio Alias is defined by four reaches; within each the climatically‐generated, region‐wide, fluvial response was modified by tectonics, base‐level change or river capture to varying degrees. In the upper part of the basin (Lucainena reach), climate was the dominant control on river development, with limited modification of the sequence by uplift of the Sierra Alhamilla and local drainage reorganization by a local river capture. Downstream of the Sierra Alhamilla in the Polopus reach, the climatic signal is dominant, but its expression is radically modified by the response to a major river capture whereby the Alias system lost up to 70% of its pre‐capture drainage area. In the reach adjacent to the Carboneras Fault Zone (Argamason reach), modification of the terrace sequence by local tectonic activity and a resultant local base‐level fall led to a major local incisional event (propagating c. 3–4 km upstream from the area of tectonic disturbance). At the seaward end of the system (El Saltador reach) Quaternary sea‐level changes modified the patterns of erosion and incision and have resulted in steep incisional terrace profiles. The signals generated by regional tectonics and the Quaternary climate change can be identified throughout the basin but those generated by ongoing local tectonics, river capture and sea‐level change are spatially restricted and define the four reaches. The connectivity of the system from the headwaters to the coast decreased through time as incision progressed, resulting in changes in local coupling characteristics. Copyright © 2012 John Wiley & Sons, Ltd.

The river it goes right on: Post-glacial landscape evolution in the upper Waipaoa River basin, eastern North Island, New Zealand

Post-glacial incision created 50 to 120m of relief in the headwaters of the Waipaoa River basin, but it is not known how the signal of incision propagated along the trunk streams. We addressed this issue by imposing previously determined long-term rates of rock uplift, that vary between 0.6 and 4mmyear−1, on the preaggradation longitudinal profile. Acting over the past 27.1±2cal.kaBP, these rates are sufficient to passively elevate the Waipaoa-1 terrace to its present level. But during the Last Glacial Maximum, rates of vertical incision failed to match those of the uplifting rocks. Thus, by the time favorable conditions for incision were reestablished after the Antarctic Cold/New Zealand Late Glacial reversal we estimate that the channel would have been elevated ≤55m above the datum the river should otherwise have maintained. The channel incised rapidly after the transition from glacial to interglacial conditions and reacquired its steady-state form in the mid-Holocene (5.5±2cal.kaBP). Thereafter, we suggest rates of incision matched rates of uplift. No knickpoints are found on the upper Waipaoa and Mangatu Rivers because incision commenced simultaneously along the entire length of the trunk streams, and the pattern of incision is consistent with the downstream decline in the rate of rock uplift. We also used hypsometric analysis to show how post-glacial incision affected the surface morphology of low order (0.1–4.3km2) drainages in the headwaters of the Waipaoa River basin. Values of the hypsometric integral are higher for proximal basins, which the incision signal did not permeate, than for low-order basins bordering the upper Waipaoa River and the lower reaches of tributaries that possessed enough erosive capacity to keep pace with incision along the mainstem. Hillslope adjustments were focused on the lower and mid-sections of these basins so that the most pronounced changes to the hypsometric curve occur in the vicinity of the toe, whereas the entire form of the hypsometric curve changes once mass wasting processes encroach onto hillslopes in the middle and upper sections of a basin.

XPB helicase regulates DNA incision by the Thermoplasma acidophilum endonuclease Bax1

Bax1 has recently been identified as a novel binding partner for the archaeal helicase XPB. We previously characterized Bax1 from Thermoplasma acidophilum as a Mg2+-dependent structure-specific endonuclease. Here we directly compare the endonuclease activity of Bax1 alone or in combination with XPB. Using several biochemical and biophysical approaches, we demonstrate regulation of Bax1 endonuclease activity by XPB. Interestingly, incision assays with Bax1 and XPB/Bax1 clearly demonstrate that Bax1 produces different incision patterns depending on the presence or absence of XPB. Using atomic force microscopy (AFM), we directly visualize and compare binding of Bax1 and XPB/Bax1 to different DNA substrates. Our AFM data support enhanced DNA binding affinity of Bax1 in the presence of XPB. Taken together, the DNA incision and binding results suggest that XPB is able to load and position Bax1 on the scissile DNA substrate, thus increasing the DNA substrate range of Bax1.

Oncoplastic Breast Reduction: Maximizing Aesthetics and Surgical Margins

Oncoplastic breast reduction combines oncologically sound concepts of cancer removal with aesthetically maximized approaches for breast reduction. Numerous incision patterns and types of pedicles can be used for purposes of oncoplastic reduction, each tailored for size and location of tumor. A team approach between reconstructive and breast surgeons produces positive long-term oncologic results as well as satisfactory cosmetic and functional outcomes, rendering oncoplastic breast reduction a favorable treatment option for certain patients with breast cancer.

Körperstraffungen

Indications for most forms of abdominoplasty are slight weight fluctuations or pregnancy. The steadily increasing number of patients with greater weight loss as well as the growing number of bariatric operations subsequently leads to a significant increase in body contouring procedures and places new challenges on plastic surgeons. After major weight loss patients present with extremely variable deformities in the lower and upper trunk as well as the extremities, which have to be treated individually with an appropriate procedure. The restoration of the lower trunk presents the first stage of the entire reconstruction process. The various modifications of abdominoplasty procedures with their various incision patterns and scar courses and the circumferential lower trunk dermatolipectomy represent advanced operations for every individual case. Plastic surgeons should be fully aware of differences and indications of every available procedure in the area of the lower trunk and should have the ability to offer the entire repertory for each individual deformity. A high postoperative patient satisfaction results from a customized procedure selection, the optimal implementation with a correspondingly low rate of complications and above-average patient care.

Kinematic implications of consequent channels on growing folds

[1] As soon as a fold begins to grow above base level, it becomes subject to erosion. A numerical model of simultaneous fold growth and river erosion captures the early stages of channel formation and delineates the evolution of longitudinal channel profiles. This numerical exploration suggests that the patterns of channel incision into growing folds can be used to guide kinematic interpretations of fold growth. Four types of fold limb growth are modeled: limb lengthening through (1) the fold crest or (2) the fold toe, (3) limb rotation, and (4) curved fold limbs due to trishear folding. Initially, the pattern of channel incision is sensitive to the kinematics of surface deformation. Subsequently, more mature streams evolve toward similar incision patterns with deepest incision near the midpoint of the longitudinal channel profile. We compare these model predictions to Rough Ridge on New Zealand's South Island, where high-resolution topographic data reveal the multitude of channels incised into the flanks of these folds. Because the opposing limbs of these folds have followed distinct deformation pathways, the early sensitivity of channel incision to deformation pathway can be examined. Furthermore, the lateral propagation of the fold through time allows for an approximate space-for-time substitution, such that the evolution of these incision patterns can be examined from early through more mature stages. This analysis indicates that the west limb of Rough Ridge has grown by limb lengthening through the toe and the east limb has grown primarily by lengthening through the crest.

Does climate change create distinctive patterns of landscape incision?

Incised fluvial systems are typically interpreted as recording geologically recent changes in either climate or tectonics. However, few diagnostic tools exist to evaluate whether particular incised landscapes primarily reflect climatic or tectonic perturbation. Here we summarize the results of a simple fluvial sediment transport model that allows us to contrast patterns of fluvial incision driven by changes in hydrology and sediment flux (“climate”) with those driven by changes in rock uplift patterns relative to sea level (“tectonics”). Our modeling suggests that there may be diagnostic differences between the spatial and temporal patterns of incision caused by these different processes. In particular, incision driven by climate change is most commonly accompanied by downstream migrating waves of incision and decreases in channel gradient, while under most circumstances incision driven by tectonics will be accompanied by upstream migrating incision and increases in channel gradient. We apply our modeling to a case study of the North American High Plains, where regionally elevated surfaces east of the Rockies have been incised up to 500 m by the fluvial systems draining the core of the range. Although this incision has been interpreted as reflecting a tectonic rejuvenation of the High Plains, our analysis suggests that climate change is at least as plausible an explanation to explain the incision of this landscape. Diagnostic differences between the climate and tectonic end‐member scenarios might be obtained via detailed study of the spatial and temporal patterns of terrace abandonment, providing a potentially fruitful target for field investigation.

River incision, circulation, and wind regime of Pleistocene Lake Bonneville, USA

Pleistocene Lake Bonneville of the western U.S. and its associated alluvial systems present a unique opportunity to understand the relationship between prevailing winds of the time, lake circulation, and river incision. The lake underwent a catastrophic flooding event ∼ 18,300 yr B.P. resulting in the incision of streams entering the lake along its eastern border. Incision patterns of twelve streams and rivers suggest that they were influenced by the prevailing circulation in the lake at the time. In order to match patterns of river incisions, simulations of lake circulation were performed with a state-of-the-art numerical model for the maximum transgressive (Bonneville) lake elevation. Simulations were conducted using the forcing of westerly and easterly prevailing winds. Simulated circulation can be described in terms of simple geostrophic balances in which the currents are generally cyclonic (counter clockwise) for westerly winds and anti-cyclonic (clockwise) for easterly winds. Irregularities in lake shorelines and bathymetry cause localized variation of this general pattern. Comparison of model output with the deflected stream incision patterns suggest that prevailing winds during the Pleistocene in the Great Basin of North America were westerly and that, unlike the interior of North America, the continental ice sheet did not exert significant influence on the climatological wind patterns of the Great Basin.

Skin-Reducing Mastectomy With Immediate Implant Reconstruction as an Indispensable Tool in the Provision of Oncoplastic Breast Services

Skin-reducing mastectomy (SRM) is a method of immediate breast reconstruction derived from a Wise breast reduction incision pattern that enables immediate subpectoral implant placement after mastectomy. Its virtue lies in the manner it provides for adequate implant coverage using muscle and a deepithelialized dermal flap, thus reducing the risk of implant extrusion and providing good inframammary contour. Our experience with this technique is elaborated. Data was collected from a prospective database in our unit from January 2006 to August 2009. Information was analyzed on indications, complications, cosmetic outcomes, and recurrence rates. A total of 89 SRMs were performed in 72 patients during the study period. This included 65 SRMs for invasive breast cancer, 7 for in-situ disease, and 17 for risk reduction. Median patient age was 44 years, and follow-up ranged from 5 to 42 months. Complications included capsular contracture in 14 patients, 2 implant infections, and 1 hematoma requiring surgical evacuation. Cosmetic outcomes were graded by patients as good to excellent in 66 (92%). No local recurrences have been detected to date. Our observations support the use of this technique as a safe, valid, and useful tool in an oncoplastic breast service.

Regional incision of the eastern margin of the Tibetan Plateau

New (U-Th)/He analyses from three elevation transects collected within river gorges that dissect the eastern margin of the Tibetan Plateau provide constraints on the rates and timing of accelerated river incision into the high-elevation, low-relief topography of the region. Apatite He data from the easternmost transect (Dadu River), ∼120 km from the plateau margin adjacent to the Sichuan Basin, indicate that rapid river incision of ∼0.33 ± 0.04 km/m.y. began at ca. 10 Ma and has continued to the present. Apatite He and zircon He data from the middle transect (Yalong River), collected ∼225 km SSW of the Dadu data, indicate that rapid river incision of ∼0.34 ± 0.02 km/m.y. began prior to ca. 14 Ma and continued until the early Quaternary, when it increased, likely in response to local uplift and erosion associated with active faults nearby. Apatite He and zircon He data from the westernmost transect (Yangtze River), ∼210 km W of the Yalong data, indicate that rapid river incision of ∼0.38 ± 0.04 km/m.y. began at or prior to ca. 10 Ma, though likely not prior to ca. 15 Ma, and has continued to the present. The regional consistency of these data indicates that the entire eastern margin of the Tibetan Plateau was being dissected by 10 Ma and that incision has been relatively constant and uniform in the region since that time; this pattern is consistent with an erosional response to broad regional uplift at or before 10 Ma. The larger amount, and earlier onset, of exhumation observed in the Yalong River gorge shows that certain areas on the eastern margin deviate from a simple regional pattern of epeirogenic uplift and subsequent river incision and probably reflect the superposition of local upper-crustal deformation and uplift on the broad regional pattern.

Field mapping and GIS visualisation of Quaternary river terrace landforms: an example from the Río Almanzora, SE Spain

Please click here to download the map associated with this article. This paper presents the mapping results of a Quaternary river terrace staircase associated with the evolution of the Río Almanzora in SE Spain. Prior to map compilation a formal landform stratigraphy was constructed from remote sensing and field reconnaissance using standard allostratigraphic procedures as outlined by the North American Stratigraphic Commission. The stratigraphic framework comprised five allomembers of the Río Almanzora Alloformation corresponding to an inset sequence of river terrace levels that document > 150 m of Quaternary fluvial incision by the Río Almanzora. The terrace stratigraphy was mapped in the field using a hand held GPS to construct control points that tracked breaks and changes in slope associated with terrace stratigraphic boundaries. The field map and survey data were compiled in a GIS geodatabase and overlaid onto a DEM and geological map data for analysis and visualisation purposes. The stratigraphic and mapping procedure outlined here follows a standard methodology for investigations of Quaternary river terrace sequences, which have traditionally been mapped by geological surveys as undifferentiated Quaternary sediments. Ultimately, map compilation was undertaken in order to facilitate reconstruction of the Quaternary fluvial history of the Río Almanzora in order to identify the key environmental controlling mechanisms (tectonics, eustacy, climate change) for driving river terrace aggradation and incision patterns. The identification of five major river terrace landform levels and integration with luminescence age data suggests a climatic control on landform development with river aggradation occurring during glacial and transition periods between glacials and interglacials. River downcutting is attributed to base-level changes linked to a long term uplift trend and climate related sea-level fluctuations.

Comparison of Penetrating Keratoplasty Performed with a Femtosecond Laser Zig-Zag Incision versus Conventional Blade Trephination

To evaluate visual outcomes and astigmatism in patients who underwent penetrating keratoplasty (PK) with 2 different incision techniques. Retrospective comparison of a consecutive surgical series. Fifty-seven consecutive patients who underwent PK at the University of California, Irvine, academic referral practice. A comparison of 49 eyes of 43 patients that underwent femtosecond laser zig-zag incision pattern PK versus 17 eyes of 14 patients that underwent conventional Barron suction trephination PK performed contemporaneously. All PKs were closed with an identical, 24-bite running nylon suture technique. Topographically determined astigmatism, best spectacle-corrected visual acuity (BSCVA), and recovery of full visual potential. The postoperative follow-up ranged from 1 to 12 months. There was a significant difference in average astigmatism between the groups at postoperative month 1 (P = 0.013) and 3 (P = 0.018). By month 3, the average astigmatism was 3 diopters (D) in the zig-zag group and 4.46 D in the conventional group. Of the patients with normal macular and optic nerve function (n(ZZ) = 32; n(con) = 14), a significant difference in BSCVA was seen at month 1 (P = 0.0003) and month 3 (P = 0.006) with 81% of the zig-zag group versus 45% of the conventional group achieving BSCVA of > or =20/40 by month 3 (P = 0.03). The femtosecond laser generated zig-zag-shaped incision results in a more rapid recovery of BSCVA and induces less astigmatism compared with conventional blade trephination PK. Proprietary commercial disclosure may be found after the references.

Spatial and Temporal Patterns of Stream Channel Incision in the Loess Region of the Missouri River

Stream channel incision is severe in the loess-dominated region of western Iowa and eastern Nebraska, with recent incision related to sediment capture by reservoirs on the Missouri River. This study confirms that the temporal pattern of incision follows the rate law proposed by Graf (1977) with half-lives ranging from two to nine years and stream channels throughout the affected watersheds approaching a new dynamic equilibrium in one to three decades. The resulting spatial pattern of incision on tributaries is demonstrated to follow a simple rule of base-level lowering at the outlet multiplied by a flow-length ratio (R 2 = 0.71). This rule is used to estimate depth of channel incision along all tributary streams of the Nebraska reach of the Missouri River and confirms that Missouri River degradation, along with other local disturbances such as channelization, is an important cause of tributary stream incision in the study area. Using the flow-length ratio rule, a spatial model of stream channel incision is developed that accounts for influences of channelization, grade controls, the erodability of geologic materials, and time.

Climate control on Quaternary coal fires and landscape evolution, Powder River basin, Wyoming and Montana

Late Cenozoic stream incision and basin excavation have strongly influenced the modern Rocky Mountain landscape, but constraints on the timing and rates of erosion are limited. The geology of the Powder River basin provides an unusually good opportunity to address spatial and temporal patterns of stream incision. Numerous coal seams in the Paleocene Fort Union and Eocene Wasatch Formations within the basin have burned during late Cenozoic incision, as coal was exposed to dry and oxygen-rich near-surface conditions. The topography of this region is dominated by hills capped with clinker, sedimentary rocks metamorphosed by burning of underlying coal beds. We use (U-Th)/He ages of clinker to determine times of relatively rapid erosion, with the assumption that coal must be near Earth's surface to burn. Ages of 55 in situ samples range from 0.007 to 1.1 Ma. Clinker preferentially formed during times in which eccentricity of the Earth's orbit was high, times that typically but not always correlate with interglacial periods. Our data therefore suggest that rates of landscape evolution in this region are affected by climate fluctuations. Because the clinker ages correlate better with eccentricity time series than with an oxygen isotope record of global ice volume, we hypothesize thatmore » variations in solar insolation modulated by eccentricity have a larger impact on rates of landscape evolution in this region than do glacial-interglacial cycles.« less

Rapid headward erosion of marsh creeks in response to relative sea level rise

Tidal creeks in Cape Romain, South Carolina, are extending rapidly onto the established marsh platform producing an unusual morphology, which remains self‐similar in time. A time‐series of aerial photographs establishes that these channels are headward eroding at an approximate rate of 1.9 m/yr. The rapid rate of headward erosion suggests that the marsh platform is in disequilibrium and unable to keep pace with high local relative sea level rise (RSLR >3.2mm/yr) through accretionary processes. Biological feedbacks play a strong role in the morphological development of the creeks. Dieback of vegetation coupled with intense burrowing by crabs produces a bare and topographically depressed region beyond the channel head toward which the channel head extends. We examine the mechanisms producing this headward extension and pinnate channel morphology, and report a new pattern of creek incision in a regime of rapid RSLR.

Safety of incomplete incision patterns in femtosecond laser–assisted penetrating keratoplasty

To evaluate the wound integrity of incomplete contoured corneal incisions created with a femtosecond laser at a refractive surgery center followed by subsequent patient transfer to a separate surgical facility for penetrating keratoplasty (PKP). Private tertiary referral center, Indianapolis, Indiana, USA. This retrospective consecutive interventional case series comprised 46 eyes that had femtosecond laser PKP. Incomplete contoured incisions were created in the recipient cornea at a refractive surgery center. Patients were then transferred to an ambulatory surgical center for PKP. The indications for PKP included keratoconus, corneal scarring, bullous keratopathy, corneal dystrophy, and failed graft. Three incision contours were used: top hat (n=26), mushroom (n=13), and zigzag (n=7). The incomplete portion of the incision was 70.0 to 300.0 microm in length. Leaving 150.0 to 300.0 microm of the lamellar ring cut incomplete did not ensure wound stability, whereas leaving 70.0 to 75.0 microm of the anterior side cut or posterior side cut incomplete provided excellent wound stability. In all eyes, the partial-thickness incisions enabled safe transport of the patient to the operating room without wound rupture, even with subsequent placement of a retrobulbar injection and a Honan balloon. Incomplete femtosecond laser incision patterns that left some collagen lamellae intact maintained sufficient corneal strength to allow safe movement of the patient to a surgical facility for PKP.