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It is now widely accepted that rivers modify their erosion rates in response to variable rock uplift rates, resulting in changes in channel slope that propagate upstream through time. Therefore, present-day river morphology may contain a record of tectonic history. The simple stream power incision model can, in principle, be used to quantify past uplift rates over a variety of spatial and temporal scales. Nonetheless, the erosional model's exponents of area and slope (m and n respectively) and 'bedrock erodibility' (k) remain poorly constrained. In this paper, we will use a geologically and geomorphically well constrained Plio-Pleistocene volcanic landscape in central Sardinia, Italy, to calibrate the stream power erosion equation and to investigate the slip rate of faults that have been seismically quiescent in the historic past. By analysing digital elevation models, geological maps and Landsat imagery, we have identified the geomorphic expression of several volcanic features (eruption centres and basaltic lava flows) and three normal faults with 6 to 8 km fault traces within the outcrop. Downstream, river longitudinal profiles show a similar transient response to relative base level fall, probably as a result of relief inversion at the edge of the volcanic outcrop. From measurements of incision, local slope and upstream catchment area across eight different rivers, we calculate n ≈ 1, m = 0.50 ± 0.02 and, using a landscape age from literature of 2.7 Ma, bedrock erodibility k = 0.10 ± 0.04 m(1−2m) Myr−1. There are also knickpoints on rivers upstream of two normal faults, and we used numerical inverse modelling of the longitudinal profiles to predict the slip rate of these faults since 2.7 Ma. The results from the inverse model show that the erosional parameter values derived in this study can produce theoretical longitudinal profiles that closely resemble observed river profiles upstream of the faults. The lowest misfit theoretical longitudinal profiles were generated by a model of temporally discontinuous footwall uplift with consistently low throw rates (<0.1 mm yr−1). The predicted footwall uplift history is similar for the two faults, both showing periods of fault slip and no fault movement since 2.7 Ma. • Faults and transient rivers identified from digital elevation models. • New graphical approaches calibrate stream power erosional model. • Incision rate proportional to channel slope and square root of upstream area • Throw rates of two normal faults predicted using inverse method. • Model predicts periods of Plio-Pleistocene activity for both faults. [ABSTRACT FROM AUTHOR]

Beach and dune morphology are spatially and temporally variable, changing over a broad range of scales simultaneously. Strong wind, waves, and storm surge from Hurricane Harvey substantially eroded the beach and dunes along the Texas coast, causing significant scarps and berms. This paper presents information about how anthropogenic activity, such as driving on the beach, affected the response and recover of a barrier island with regard to the post-storm resiliency along the Texas-Gulf of Mexico coast by comparing two adjacent 7 km stretches of coast: a driving section and a limited-access section. A collection of field photos, aerial imagery, and a September 2016 LiDAR-derived digital elevation model (DEM) dataset provide information on pre-storm morphology, while field photos, taken only 3 days after Hurricane Harvey made landfall, and a structure-from-motion (SfM)-derived DEM and imagery provide qualitative and quantitative information about the post-storm morphology. While beach and dune erosion in the non-driving section was restricted entirely to the beach and incipient dune system, the driving section exhibited complex patterns of erosion and deposition along the beach and the entire foredune profile was altered. Despite the hurricane making landfall north of the study site and closer to the non-driving section, beach-dune erosion and scarping was greatest in the southern section which is accessible to public vehicles. Results demonstrate that human activity affects the response and recovery of the beach-dune system along the Gulf side of the island by decreasing alongshore variability in erosion-deposition and limiting vegetative and geomorphic recovery. Unlabelled Image • Driving on the beach affects beach-dune response to and recovery following a storm. • Non-driving areas show substantial evidence of recovery within 6 months post-storm. • Driving on the beach limits incipient foredune development and recovery. • Limiting low dune recovery can reinforce the effects of framework geology. [ABSTRACT FROM AUTHOR]

This paper documents ranges of streambed and bank erosion observed across suburban northern Kentucky via time-series surveys at 61 stream monitoring sites from the last ~10 yr. Average erosion rates in streams draining undeveloped watersheds (<5% total impervious area, TIA) were nominal: 0.5 cm/yr of incision (range of −5.8 to 11 cm/yr) and 1.0 cm/yr of widening (range of −58 to 20 cm/yr). By contrast, streams draining developed watersheds (>5% TIA) averaged 1.5 cm/yr of incision (range of −9.2 to 36 cm/yr) and 9.4 cm/yr of widening (range of −11 to 61 cm/yr). The suburban streams also followed predictable patterns of evolution consistent with the "classic" Channel Evolution Model (CEM) of Schumm et al. (1984) , with the initial incision period (Stage 2) coinciding with bed coarsening followed by widening (Stage 3). Out of 45 sites draining >5% TIA, only four were in a state of dynamic equilibrium (Stage 1), two of which were attributable to stabilization via stream restoration and another was attributable to an upstream stormwater retrofit that substantially restricted erosive discharges. The other stable suburban site drained a watershed that was only 6.5% TIA and was just upstream of a reach undergoing incision and headcutting, implying that it would likely be experiencing incision (Stage 2) soon. Although the suburban sites spanned a gradient of development age and extent, >90% fell into unstable CEM categories (Stages 2 through 4), with only one site exhibiting features emblematic of potential geomorphic recovery (Stage 4 trending to Stage 5), attributable to an upstream stormwater retrofit. This case study underscores the predictable nature of long-term channel instability in gravel/cobble streams draining conventionally-developed suburban watersheds in support of more mechanistically based stormwater management strategies tailored to prevent the geomorphic degradation commonly associated with the urban stream syndrome. [ABSTRACT FROM AUTHOR]

Examples of partial avulsion and river bifurcation around large stable islands make up a small but locally important portion of the total length of rivers in the Piedmont physiographic province of North Carolina (U.S.). Despite remaining ecologically significant, the partially abandoned (or "abandoning") branches along such reaches have received less attention than the often dominant newly created branches. The existence of perennial flow through abandoning channels may be contingent upon their ability to rapidly adjust their morphologies to declining flows. In this paper we study the response of a partially abandoned channel of the upper Catawba River in North Carolina to major loss of flow following flood-induced partial avulsion in 1977. Human activities have strongly modified the floodplain in this area, assisting the avulsion and possibly influencing the natural erosion and sedimentation processes responsible for subsequent adjustments of the abandoning channel. Using a combination of downstream gaging data, flow estimation functions, channel mapping, and hydraulic geometry analyses, we assess the degree to which channel capacity reduction matches the amount of post-avulsion diminished discharge. Construction of fluvial sediment benches inset within the old single-thread channel has occurred along 83% of the channel's length, and most of these have crest elevations in the 1–2 yr flood stage range. Hydraulic geometry reconstructions indicate that length-weighted mean channel width, depth, and capacity deviate from predicted values by 36%, 18%, and 61%. Thus, channel cross-section dimensions for the abandoning channel appear substantially larger than predicted, a condition that is potentially discordant with a hypothetical necessity of rapid width adjustment for maintaining an open channel, depending on what constitutes a rapid rate of adjustment. Variables such as the morphology of the bifurcation node and load properties also influence the longevity of abandoning channels, and rates of adjustment or infilling can vary widely. Stratigraphic, pedogenic, and vegetative evidence together suggest that channel narrowing via inset bench formation has occurred gradually over at least two or more decades following initial flow loss. Comparisons with channel dimensions predicted from existing Piedmont regional curves show greater agreement, supporting the contention that Piedmont valley characteristics exercise at least as strong an influence on channel morphology as does the higher relief watershed topography and associated flow regime. The presence of perennial flow and active geomorphological processes in the abandoning channel indicates that it remains part of a dynamic and ecologically significant river reach, despite being currently designated as land in county land parcel records. • Partial avulsion of the upper Catawba River (U.S.) occurred in 1977. • The new channel course was influenced by floodplain gravel mining. • Contraction of the abandoning channel has occurred via bench formation. • Hydraulic reconstruction indicates contraction not commensurate with discharge reduction. • Comparison to regional curve predictions indicate the importance of valley setting. [ABSTRACT FROM AUTHOR]

Rillenkarren are small scale, straight, narrow solution channels that head at the crest of a bare rock slope and are extinguished downslope. In this paper the applicability of 3D-photo reconstruction technique of the rock surface is proposed for capturing the rillenkarren morphometry on gypsum. At first, the measurements are used to assess a relationship between the width/depth ratio and the depth of the rillenkarren. The exponent of this power relationship resulted different from the theoretical value - 0.5, confirming that the cross-section profiles of a rillenkarren can have a shape different from parabolic. The analysis developed for the cross-section area, the perimeter and the hydraulic radius established that the formation process is able to deep and enlarge the channel. The proposed model of the measured longitudinal profiles confirmed that the profile shape can be characterized by a flex point which divide the upstream concave part from the downstream convex one. According to previous studies on soil erosion features (rills, ephemeral gullies and gullies) the relationship between the rillenkarren length and its volume was expressed by a power equation. The comparison between rillenkarren and soil erosion features allowed to conclude that a single exponent (equal to 1.1) can be applied while the coefficient is characteristic of the feature and represents the influence of channel depth and width. Finally a model of rillenkarren morphometry, deduced applying the dimensional analysis and self-similarity, was applied to the measurements. This analysis demonstrated that a single dimensionless relationship is applicable to rillenkarren and rills, ephemeral gullies and gullies, assessing that a morphometric similarity exists between these different erosion features. • Rillenkarren morphometry is captured by a 3D-photo reconstruction technique. • The cross-section profile of a rillenkarren can have a shape different from parabolic. • The relationship between rillenkarren length and its volume is a power equation. • Rillenkarren formation is modelled by dimensional analysis and self-similarity. [ABSTRACT FROM AUTHOR]