Assessing the impact of urbanization on storm runoff in a peri-urban catchment using historical change in impervious cover

his paper investigates changes in storm runoff resulting from the transformation of previously rural landscapes into peri-urban areas. Two adjacent catchments (∼5 km2) located within the town of Swindon in the United Kingdom were monitored during 2011 and 2012 providing continuous records of rainfall, runoff and actual evaporation. One catchment is highly urbanized and the other is a recently developed peri-urban area containing two distinct areas of drainage: one with mixed natural and storm drainage pathways, the other entirely storm drainage. Comparison of observed storm hydrographs showed that the degree of area serviced by storm drainage was a stronger determinant of storm runoff response than either impervious area or development type and that little distinction in hydrological response exists between urban and peri-urban developments of similar impervious cover when no significant hydraulic alteration is present. Historical levels of urbanization and impervious cover were mapped from the 1960s to the 2010s based on digitized historical topographic maps and were combined with a hydrological model to enable backcasting of the present day storm runoff response to that of the catchments in their earlier states. Results from the peri-urban catchment showed an increase in impervious cover from 11% in the 1960s to 44% in 2010s, and introduction of a large-scale storm drainage system in the early 2000s, was accompanied by a 50% reduction in the Muskingum routing parameter k, reducing the characteristic flood duration by over 50% while increasing peak flow by over 400%. Comparisons with changes in storm runoff response in the more urban area suggest that the relative increase in peak flows and reduction in flood duration and response time of a catchment is greatest at low levels of urbanization and that the introduction of storm water conveyance systems significantly increases the flashiness of storm runoff above that attributed to impervious area alone. This study demonstrates that careful consideration is required when using impervious cover data within hydrological models and when designing flood mitigation measures, particularly in peri-urban areas where a widespread loss in pervious surfaces and alteration of drainage pathways can significantly alter the storm runoff response. Recommendations include utilizing more refined urban land use typologies that can better represent physical alteration of hydrological pathways

Transient Storage as a Function of Geomorphology, Discharge, and Permafrost Active Layer Conditions in Arctic Tundra Streams

Transient storage of solutes in hyporheic zones or other slow-moving stream waters plays an important role in the biogeochemical processes of streams. While numerous studies have reported a wide range of parameter values from simulations of transient storage, little field work has been done to investigate the correlations between these parameters and shifts in surface and subsurface flow conditions. In this investigation we use the stream properties of the Arctic (namely, highly varied discharges, channel morphologies, and subchannel permafrost conditions) to isolate the effects of discharge, channel morphology, and potential size of the hyporheic zone on transient storage. We repeated stream tracer experiments in five morphologically diverse tundra streams in Arctic Alaska during the thaw season (May–August) of 2004 to assess transient storage and hydrologic characteristics. We compared transient storage model parameters to discharge (Q), the Darcy-Weisbach friction factor (f), and unit stream power (ω). Across all studied streams, permafrost active layer depths (i.e., the potential extent of the hyporheic zone) increased throughout the thaw season, and discharges and velocities varied dramatically with minimum ranges of eight-fold and four-fold, respectively. In all reaches the mean storage residence time (tstor) decreased exponentially with increasing Q, but did not clearly relate to permafrost active layer depths. Furthermore, we found that modeled transient storage metrics (i.e., tstor, storage zone exchange rate (αOTIS), and hydraulic retention (Rh)) correlated better with channel hydraulic descriptors such as f and ω than they did with Q or channel slope. Our results indicate that Q is the first-order control on transient storage dynamics of these streams, and that f and ω are two relatively simple measures of channel hydraulics that may be important metrics for predicting the response of transient storage to perturbations in discharge and morphology in a given stream

The Interdomain Linker of AAV-2 Rep68 Is an Integral Part of Its Oligomerization Domain: Role of a Conserved SF3 Helicase Residue in Oligomerization

The four Rep proteins of adeno-associated virus (AAV) orchestrate all aspects of its viral life cycle, including transcription regulation, DNA replication, virus assembly, and site-specific integration of the viral genome into the human chromosome 19. All Rep proteins share a central SF3 superfamily helicase domain. In other SF3 members this domain is sufficient to induce oligomerization. However, the helicase domain in AAV Rep proteins (i.e. Rep40/Rep52) as shown by its monomeric characteristic, is not able to mediate stable oligomerization. This observation led us to hypothesize the existence of an as yet undefined structural determinant that regulates Rep oligomerization. In this document, we described a detailed structural comparison between the helicase domains of AAV-2 Rep proteins and those of the other SF3 members. This analysis shows a major structural difference residing in the small oligomerization sub-domain (OD) of Rep helicase domain. In addition, secondary structure prediction of the linker connecting the helicase domain to the origin-binding domain (OBD) indicates the potential to form α-helices. We demonstrate that mutant Rep40 constructs containing different lengths of the linker are able to form dimers, and in the presence of ATP/ADP, larger oligomers. We further identified an aromatic linker residue (Y224) that is critical for oligomerization, establishing it as a conserved signature motif in SF3 helicases. Mutation of this residue critically affects oligomerization as well as completely abolishes the ability to produce infectious virus. Taken together, our data support a model where the linker residues preceding the helicase domain fold into an α-helix that becomes an integral part of the helicase domain and is critical for the oligomerization and function of Rep68/78 proteins through cooperative interaction with the OBD and helicase domains

Advancing river corridor science beyond disciplinary boundaries with an inductive approach to catalyze hypothesis generation

A unified conceptual framework for river corridors requires synthesis of diverse site-, method- and discipline-specific findings. The river research community has developed a substantial body of observations and process-specific interpretations, but we are still lacking a comprehensive model to distill this knowledge into fundamental transferable concepts. We confront the challenge of how a discipline classically organized around the deductive model of systematically collecting of site-, scale-, and mechanism-specific observations begins the process of synthesis. Machine learning is particularly well-suited to inductive generation of hypotheses. In this study, we prototype an inductive approach to holistic synthesis of river corridor observations, using support vector machine regression to identify potential couplings or feedbacks that would not necessarily arise from classical approaches. This approach generated 672 relationships linking a suite of 157 variables each measured at 62 locations in a 5th order river network. Eighty four percent of these relationships have not been previously investigated, and representing potential (hypothetical) process connections. We document relationships consistent with current understanding including hydrologic exchange processes, microbial ecology, and the River Continuum Concept, supporting that the approach can identify meaningful relationships in the data. Moreover, we highlight examples of two novel research questions that stem from interpretation of inductively-generated relationships. This study demonstrates the implementation of machine learning to sieve complex data sets and identify a small set of candidate relationships that warrant further study, including data types not commonly measured together. This structured approach complements traditional modes of inquiry, which are often limited by disciplinary perspectives and favor the careful pursuit of parsimony. Finally, we emphasize that this approach should be viewed as a complement to, rather than in place of, more traditional, deductive approaches to scientific discovery

Formulation and Validation of a Scale of Antisemitic Stereotypes (SASS)

Antisemitism remains a serious issue in the United States, but lacks up-to-date, theory-based measurement. The stereotype content model (SCM) explains antisemitic stereotypes as an envious prejudice toward stereotypically high-competence, low-warmth Jewish people (Fiske, Cuddy, Glick, & Xu, 2002). Developing a Scale of Anti-Semitic Stereotypes (SASS) tentatively supported the SCM: participants’ spontaneously generated competence items were similar to those included in the Scale of Anti-Asian American Stereotypes (SAAAS; Lin et al., 2005), another envious prejudice. However, exploratory factor analysis did not reveal a two-factor structure, but an undifferentiated antipathy towards Jews. Ascertaining the scale’s predictive validity found correlations between SASS scores and participants’ knowledge about Jewish culture and people, and number of subtypes of Jewish people identified, but not the number of Jewish friends reported. SASS scores not only correlated with respondents’ right-wing authoritarianism, social dominance orientation, and political conservatism, but also predicted anti-Black racism and Anti-Asian American stereotypes. SASS scores correlated with implicit attitudes about, and blatant dehumanization of, Jewish people, as well as systematic overestimations of the number of Jewish professionals, especially bankers. Like SASS factors, IATs revealed expected implicit associations between Jewish people and coldness, but also between Jewish people and incompetence. Future research should investigate whether people might differentially evaluate different subtypes of Jews: “Secular” Jews may seem high in competence but low in warmth, consistent with international SCM ratings; “religious” Jews (Orthodox) may fit a different pattern. Keywords: Jewish, Judaism, Antisemitism, stereotype content model (SCM), blatant dehumanization, implicit attitudes, subtypin

Using Turbidity to Determine Total Suspended Solids in Urbanizing Streams in the Puget Lowlands

The replacement of forestland with impervious surfaces during urbanization can have significant effects on watershed hydrology and the quality of stormwater runoff. One component of water quality, total suspended solids (TSS), is both a significant part of physical and aesthetic degradation and a good indicator of other pollutants, particularly nutrients and metals that are carried on the surfaces of sediment in suspension. We investigated whether turbidity could produce a satisfactory estimate of TSS in urbanizing streams of the Puget Lowlands. A log-linear model showed strong positive correlation between TSS and turbidity (R2 = 0.96) with a regression equation of ln(TSS) = 1.32 ln(NTU) + C, with C not significantly different than 0 for 8 of the 9 sampled streams. These results strongly suggest that turbidity is a suitable monitoring parameter where water-quality conditions must be evaluated, however logistical and/or financial constraints make an intensive program of TSS sampling impractical

FracFit: A Robust Parameter Estimation Tool for Fractional Calculus Models

Anomalous transport cannot be adequately described with clas- sical Fickian advection-dispersion equations (ADE) with constant coefficients. Rather, fractional calculus models may be used, which capture salient fea- tures of anomalous transport (e.g. skewness and power-law tails). FracFit is a parameter estimation tool based on space- and time-fractional models used by the hydrology community. Currently, four fractional models are sup- ported: 1) space fractional advection-dispersion equation (sFADE), 2) time- fractional dispersion equation with drift (TFDE), 3) fractional mobile-immobile (FMIM) equation , and 4) temporally tempered L evy motion (TTLM). Model solutions using pulse initial conditions and continuous injections are eval- uated using stable distributions or subordination integrals. Parameter esti- mates are extracted from measured breakthrough curves (BTCs) using a weighted nonlinear least squares (WNLS) algorithm. Optimal weights for BTCs for pulse initial conditions and continuous injections are presented. Two sam- ple applications are analyzed: 1)pulse injection BTCs in the Selke river and 2) continuous injection laboratory experiments using natural organic mat- ter. Model parameters are compared across models and goodness-of- t met- rics are presented, facilitating model evaluation.Peer reviewe