Topography is a reflection of the tectonic and geodynamic processes that act to uplift the Earth's surface and the erosional processes that work to return it to base level. Numerous studies have shown that topography is a sensitive recorder of tectonic signals. A quasi-physical understanding of the relationship between river incision and rock uplift has made the analysis of fluvial topography a popular technique for deciphering relative, and some argue absolute, histories of rock uplift. Here we present results from a study of the fluvial topography from south-central Crete, demonstrating that river longitudinal profiles indeed record the relative history of uplift, but several other processes make it difficult to recover quantitative uplift histories. Prior research demonstrates that the south-central coastline of Crete is bound by a large ( ∼ 100 km long) E–W striking composite normal fault system. Marine terraces reveal that it is uplifting between 0.1 and 1.0 mm yr⁻¹. These studies suggest that two normal fault systems, the offshore Ptolemy and onshore South-Central Crete faults, linked together in the recent geologic past (ca. 0.4–1 My BP). Fault mechanics predict that when adjacent faults link into a single fault the uplift rate in footwalls of the linkage zone will increase rapidly. We use this natural experiment to assess the response of river profiles to a temporal jump in uplift rate and to assess the applicability of the stream power incision model to this setting. Using river profile analysis we show that rivers in south-central Crete record the relative uplift history of fault growth and linkage as theory predicts that they should. Calibration of the commonly used stream power incision model shows that the slope exponent, n, is ∼ 0.5, contrary to most studies that find n ≥ 1. Analysis of fluvial knickpoints shows that migration distances are not proportional to upstream contributing drainage area, as predicted by the stream power incision model. Maps of the transformed stream distance variable, χ, indicate that drainage basin instability, drainage divide migration, and river capture events complicate river profile analysis in south-central Crete. Waterfalls are observed in southern Crete and appear to operate under less efficient and different incision mechanics than assumed by the stream power incision model. Drainage area exchange and waterfall formation are argued to obscure linkages between empirically derived metrics and quasi-physical descriptions of river incision, making it difficult to quantitatively interpret rock uplift histories from river profiles in this setting. Karst hydrology, break down of assumed drainage area discharge scaling, and chemical weathering might also contribute to the failure of the stream power incision model to adequately predict the behavior of the fluvial system in south-central Crete.

The ;400 km2 Clearwater River basin, located on the Pacific flank of the actively uplifting Olympic Mountains of western Washington State, contains a well-pre- served flight of Holocene fluvial terraces. We have collected a large data set of nu- meric ages from these terraces that is used to elucidate the geomorphic, fluvial, active tectonic, and climatic processes that oper- ate at Holocene spatial and temporal scales. Detailed field mapping reveals three prom- inent Holocene straths and their overlying terrace deposits. Terrace ages fall into three broad ranges: ca. 9000-11 000 yr B.P. (Qt4), 4000-8000 yr B.P. (Qt5), and 0-3000 yr B.P. (Qt6). Terrace deposit stratigraphy, sedimentology, and age distributions allow us to consider two alternative models for their genesis. The favored model states that the terrace ages are coincident with lateral incision of the Clearwater channel, em- placement of the terrace alluvium, and the carving of the straths. Vertical incision of the Clearwater channel was primarily rel- egated to the brief (;1000 yr) intervals when we have no record of terraces. Alter- natively, the straths were carved as the channel incised vertically during the brief time periods between dated terrace depos- its, and the terrace ages record a subse- quent long time of alluviation atop the straths and concomitant termination of ver- tical incision. In both models, we envision a Clearwater River channel at or near ca- pacity with a temporally variable rate of both lateral and vertical incision. Small de- viations from this at-capacity condition are driven by variations in the liberation and delivery of hillslope sediment to the chan- nel. We consider several causes for variable hillslope sediment flux in this tectonically active setting including Holocene climate change and ground accelerations related to earthquakes. Holocene rates of vertical in- cision are reconstructed along nearly the entire Clearwater Valley from the wide dis- tribution of dated terraces. Incision rates clearly increase upstream, mimicking a pat- tern documented for Pleistocene terraces in the same basin; however, the rates are 2-3 times those determined for the Pleistocene terraces. The faster Holocene incision rates may be interpreted in terms of an increase in the rates of rock uplift. However, we fa- vor an alternative explanation in which the Holocene rates represent a channel rapidly reacquiring its stable, graded concavity fol- lowing protracted periods of time in the Pleistocene when it could not accomplish any vertical incision into tectonically uplift- ed bedrock because the channel was raised above the bedrock valley bottom by climat- ically induced alluviation. These results il- lustrate how, even in tectonically active set- tings, representative rates of rock uplift inferred from studies of river incision should be integrated over at least one gla- cial-interglacial cycle.

Modern satellite networks with rapid image acquisition cycles allow for near-real-time imaging of areas impacted by natural hazards such as mass wasting, flooding, and volcanic eruptions. Publicly accessible multi-spectral datasets (e.g., Landsat, Sentinel-2) are particularly helpful in analyzing the spatial extent of disturbances, however, the datasets are large and require intensive processing on high-powered computers by trained analysts. HazMapper is an open-access hazard mapping application developed in Google Earth Engine that allows users to derive map and GIS-based products from Sentinel or Landsat datasets without the time- and cost-intensive resources required for traditional analysis. The first iteration of HazMapper relies on a vegetation-based metric, the relative difference in the normalized difference vegetation index (rdNDVI), to identify areas on the landscape where vegetation was removed following a natural disaster. Because of the vegetation-based metric, the tool is typically not suitable for use in desert or polar regions. HazMapper is not a semi-automated routine but makes rapid and repeatable analysis and visualization feasible for both recent and historical natural disasters. Case studies are included for the identification of landslides and debris flows, wildfires, pyroclastic flows, and lava flow inundation. HazMapper is intended for use by both scientists and non-scientists, such as emergency managers and public safety decision-makers.