Description: Optimising 4-D surface change detection: an approach for capturing rockfall magnitude–frequency Jack G. Williams, Nick J. Rosser, Richard J. Hardy, Matthew J. Brain, and Ashraf A. Afana Earth Surf. Dynam., 6, 101-119, https://doi.org/10.5194/esurf-6-101-2018, 2018 We present a method to analyse surface change using 3-D data collected at hourly intervals. This is applied to 9000 surveys of a failing rock slope, acquired over 10 months. A higher proportion and frequency of small rockfall is observed than in less-frequent (e.g. monthly) monitoring. However, quantifying longer-term erosion rates may be more suited to less-frequent data collection, which contains lower accumulative errors due to the number of surveys and the lower proportion of small events.

Description: How to explain variations in sea cliff erosion rates? Insights from a literature synthesis Mélody Prémaillon, Vincent Regard, Thomas J. B. Dewez, and Yves Auda Earth Surf. Dynam. Discuss., https//doi.org/10.5194/esurf-2018-12,2018 Manuscript under review for ESurf (discussion: open, 0 comments) Coastal erosion is of major concern for society, our study focus on rocky coast whose evolution remains poorly understood. We use the increasing number of erosion-related data and compiled it for better understanding how and how much rocky coasts erode. We found that rock resistance explain in first order erosion rates whereas influence of climate and sea is secondary. Weak rock coasts loose in median 23 meters per century, about ten times more than hard rock coasts.

Description: Mechanical State of Gravel Soil in Mobilization of Rainfall-Induced Landslide in Wenchuan seismic area, Sichuan province, China Liping Liao, Yunchuan Yang, Zhiquan Yang, Yingyan Zhu, Jin Hu, and D. H. Steve Zou Earth Surf. Dynam. Discuss., https//doi.org/10.5194/esurf-2018-15,2018 Manuscript under review for ESurf (discussion: open, 0 comments) Although gravel soils generated by seismic shaking in Wenchuan earthquake area have subjected to natural consolidation process for nearly ten years, geological hazards, such as slope failures with ensuing landslides, frequently are haunting the area. In this paper, artificial flume model tests and triaxial tests were used to make close observation on the mechanical state of gravel soil in Wenchuan seismic area. The results showed that: (1) The timing and patterns of landslide initiations were closely related to their initial dry densities, and the initiation processes were accompanied with a variation of dry density and void ratio; (2) Fine particle migration in soil and coarse-fine particle content rearrangement contributed to the internal micro structure reorganization, which was supposed to be the main reason for variation of dry density and void ratio; (3) Gravel soils with unchanged grain compositions, if under the same hydrostatic compression, they approached to an identical critical void ratio to fail; (4) The mechanical state of certain sort of gravel soil can be identified by its relative position between state parameter ( e, p' ) and e c -p' planar critical state line; (5) Gravel soil slope failed and then evolved into landslide under lasting rainfall leaching, while in gravel slope there co-existed soil dilatation and contraction, but the dilatation was dominant. Above research findings not only could be used to interpret landslide initiation but also would provide an insight for landslide warning forecast of gravel slope in seismic area.

Description: Effect of changing vegetation on denudation (part 1): Predicted vegetation composition and cover over the last 21 thousand years along the Coastal Cordillera of Chile Christian Werner, Manuel Schmid, Todd A. Ehlers, Juan Pablo Fuentes-Espoz, Jörg Steinkamp, Matthew Forrest, Johan Liakka, Antonio Maldonado, and Thomas Hickler Earth Surf. Dynam. Discuss., https//doi.org/10.5194/esurf-2018-14,2018 Manuscript under review for ESurf (discussion: open, 0 comments) Vegetation is crucial for modulating rates of denudation and landscape evolution, and is directly influenced by climate conditions and atmospheric CO 2 concentrations. Using transient climate data and a state-of-the-art dynamic vegetation model we simulate the vegetation composition and cover from the Last Glacial Maximum to present along the Coastal Cordillera of Chile. In part 2 we assess the landscape response to transient climate and vegetation cover using a landscape evolution model.

Description: Morphology of bar-built estuaries: relation between planform shape and depth distribution Jasper R. F. W. Leuven, Sanja Selaković, and Maarten G. Kleinhans Earth Surf. Dynam. Discuss., https//doi.org/10.5194/esurf-2018-18,2018 Manuscript under review for ESurf (discussion: open, 0 comments) Fluvial-tidal transitions in estuaries are used as major shipping fairways and are characterised by complex bar and channel patterns with a large biodiversity. Habitat suitability assessment and study of interactions between morphology and ecology therefore require bathymetric data. While imagery offers data of planform estuary dimensions, only for a few natural estuaries bathymetries are available. Here we study the relation between along-channel planform geometry, obtained as the outline from imagery, and hypsometry, which characterises the distribution of along-channel and cross-channel bed-levels. We fitted the original function of Strahler (1952) to bathymetric data along four natural estuaries. Comparison to planform estuary shape shows that hypsometry is concave at narrow sections with large channels, while complex bar morphology results in more convex hypsometry. We found a relation between hypsometric function shape and the degree to which the estuary width deviates from an ideal convergent estuary, which is calculated from river width and mouth width. This implies that the occurring bed level distributions depend on inherited Holocene topography and lithology. Our new empirical function predicts hypsometry and along-channel variation in intertidal and subtidal width. Combination with the tidal amplitude allows an estimate of inundation duration. A validation of the results on available bathymetry shows that predictions of intertidal and subtidal area are accurate within a factor 2 for estuaries of different size and character. Locations with major human influence deviate from the general trends, because dredging, dumping, land reclamation and other engineering measures cause local deviations from the expected bed-level distributions. The bathymetry predictor can be used to characterise and predict estuarine subtidal and intertidal morphology in data-poor environments.

Description: A hydroclimatological approach to predicting regional landslide probability using Landlab Ronda Strauch, Erkan Istanbulluoglu, Sai Siddhartha Nudurupati, Christina Bandaragoda, Nicole M. Gasparini, and Gregory E. Tucker Earth Surf. Dynam., 6, 49-75, https://doi.org/10.5194/esurf-6-49-2018, 2018 We develop a model of annual probability of shallow landslide initiation triggered by soil water from a hydrologic model. Our physically based model accommodates data uncertainty using a Monte Carlo approach. We found elevation-dependent patterns in probability related to the stabilizing effect of forests and soil and slope limitation at high elevations. We demonstrate our model in Washington, USA, but it is designed to run elsewhere with available data for risk planning using the Landlab.

Description: Alluvial cover controlling the width, slope and sinuosity of bedrock channels Jens Martin Turowski Earth Surf. Dynam., 6, 29-48, https://doi.org/10.5194/esurf-6-29-2018, 2018 Bedrock channels are a key component of mountainous landscapes. Here, a new model of the steady-state morphology, including channel width, slope and sinuosity, is derived from process physics considerations. The model compares favourably to observed scaling relations.

Description: How concave are river channels? Simon M. Mudd, Fiona J. Clubb, Boris Gailleton, and Martin D. Hurst Earth Surf. Dynam. Discuss., https//doi.org/10.5194/esurf-2018-7,2018 Manuscript under review for ESurf (discussion: open, 1 comment) Rivers can reveal information about erosion rates, tectonics, and climate. In order to make meaningful inferences about these influences one must be able to compare headwaters to downstream parts of the river network. We describe new methods for normalizing river steepness for drainage area to better understand how rivers record erosion rates in eroding landscapes.

Description: Numerical modelling of landscape and sediment flux response to precipitation rate change John J. Armitage, Alexander C. Whittaker, Mustapha Zakari, and Benjamin Campforts Earth Surf. Dynam., 6, 77-99, https://doi.org/10.5194/esurf-6-77-2018, 2018 We explore how two landscape evolution models respond to a change in climate. The two models are developed from a divergent assumption on the efficiency of sediment transport. Despite the different resulting mathematics, both numerical models display a similar functional response to a change in precipitation. However, if we model sediment transport rather than assume it is instantaneously removed, the model responds more rapidly, with a response time similar to that observed in nature.

Description: Scales of collective entrainment and intermittent transport in collision-driven bed load Dylan B. Lee and Doug Jerolmack Earth Surf. Dynam. Discuss., https//doi.org/10.5194/esurf-2018-8,2018 Manuscript under review for ESurf (discussion: open, 3 comments) The transport of pebbles in a river is smooth and continuous under high flow conditions, but under typical flows becomes erratic and unpredictable. We perform experiments to learn more about the origins of this unpredictable, intermittent behavior. Our results show that this unpredictability is similar to how infrequent avalanches occur in a sandpile. Transport events are similar in size but become more infrequent and erratic as the river transports less and less sediment.