Hutchison Medallist 1. Wave-Dominated to Tide-Dominated Coastal Systems: A Unifying Model for Tidal Shorefaces and Refinement of the Coastal- Environments Classification Scheme

Coastal depositional systems are normally classified based on the relative input of wave, tide, and river processes. While wave- through to river-dominated environments are well characterized, environments along the wave-to-tide continuum are relatively poorly understood and this limits the reliability and utility of coastal classification schemes. Two tidal shoreface models, open-coast tidal flats (OCTF) and tidally modulated shorefaces (TMS), have been introduced for mixed wave-tide coastal settings. Following nearly two decades of research on tidal shorefaces, a number of significant insights have been derived, and these data are used here to develop a unified model for such systems. First, OCTFs are components of larger depositional environments, and in multiple published examples, OCTFs overlie offshore to lower shoreface successions that are similar to TMS. Consequently, we combine OCTFs and TMSs into a single tidal shoreface model where TMS (as originally described) and TMS-OCTF successions are considered as variants along the wave-tide continuum. Second, tidal shoreface successions are preferentially preserved in low- to moderate-wave energy environments and in progradational to aggradational systems. It is probably difficult to distinguish tidal shorefaces from their storm-dominated counterparts. Third, tidal shorefaces, including both TMSs and OCTFs, should exhibit tidally modulated storm deposits, reflecting variation in storm-wave energy at the sea floor resulting from the rising and falling tide. They may also exhibit interbedding of tidally generated structures (e.g. double mud drapes or bidirectional current ripples), deposited under fairweather conditions, and storm deposits (e.g. hummocky cross-stratification) through the lower shoreface and possibly into the upper shoreface.The development of the tidal shoreface model sheds light on the limitations of the presently accepted wave-tide-river classification scheme of coastal environments and a revised scheme is presented. In particular, tidal flats are components of larger depositional systems and can be identified in the rock record only in settings where intertidal and supratidal deposits are preserved; consequently, they should not represent the tide-dominated end-member of coastal systems. Instead, we suggest that tide-dominated embayments should occupy this apex. Tide-dominated embayments exhibit limited wave and river influence and include a wide range of geomorphological features typically associated with tidal processes, including tidal channels, bars and flats.

A Proposal to Classify and Assess Ecological Status in Mediterranean Temporary Rivers: Research Insights to Solve Management Needs

The biomonitoring methods implemented by water authorities are mostly developed for perennial rivers, and do not apply to temporary rivers (TRs). We propose a new classification for TRs to better assess their ecological status. It arises from the LIFE+ TRivers project, which was conducted in the Catalan and the Júcar Mediterranean river basin districts (RBD). The European Water Framework Directive (WFD) provided two systems to set river types (systems A or B from Annex II), which have been officially used by water authorities across Europe to set “national river types” (NRTs). However, essential hydrological variables for TRs are largely omitted. NRTs established according to the WFD were compared with TR categories obtained by using a rainfall-runoff model, “natural flows prescribed regimes” (NFPRs), and with “aquatic phases regimes” (APRs) calculated by using TREHS software. The biological quality indices currently used in Spain, based on macroinvertebrates and diatoms (IBMWP, IMMI-T, and IPS), were compared with a “general degradation” gradient in order to analyze the two TR river classification procedures (NFPR and APR). The results showed that NRTs did not properly classify TRs, and that the APR classification identified ecologically meaningful categories, especially those related to stagnant phases. Four “management temporary river categories” based on APRs are proposed to be used for water managers to properly assess the ecological status of TRs.

Identificação de Estilos Fluviais na Bacia do Rio Macabu (RJ) a Serem Aplicados na Gestão dos Recursos Hídricos

A pesquisa foi desenvolvida na Bacia do Rio Macabu que integra a Região Hidrográfica IX do Baixo Paraíba do Sul e Itabapoana e, assim como várias regiões hidrográficas fluminenses, apresenta longo histórico de intervenções antrópicas dentro e fora dos canais fluviais. O objetivo do trabalho é apresentar mapeamento dos Estilos Fluviais identificados na Bacia do rio Macabu, considerando-se a dinâmica atual dos processos geomorfológicos e hidrogeomorfológico a serem aplicados na gestão dos recursos hídricos. O mapeamento e classificação dos segmentos dos rios e suas tipologias foram realizados com base na aplicação de parâmetros morfométricos, para a avaliação dos controles regionais e locais sobre a forma e o comportamento do rio, no confinamento do vale, na forma em planta de toda a extensão do canal e nas unidades geomorfológicas do fundo de vale. Os resultados mostram que a compartimentação do relevo possibilita a ocorrência de diferentes feições fluviais, exerce controle regional no sistema fluvial e tem influência sobre característica do vale. Dessa forma, a configuração espacial dos compartimentos determina os padrões de comportamento em cada setor. Foram identificados oito Estilos Fluviais cuja diferenciação entre os segmentos permite compreender como os processos e formas se caracterizam, integram e se distribuem dentro do sistema fluvial. De um modo geral, a bacia do rio Macabu se expressa como um ambiente múltiplo e complexo, com muitas problemáticas relacionadas aos seus usos e modificações. Os resultados representam parte dos subsídios necessários para uma gestão eficiente e eficaz e para a tomada de decisão. Identification of River Styles in the Macabu Basin (RJ) to be Applied in Water Resource Management A B S T R A C TThe research was developed in the Macabu Basin that integrates the Lower Paraíba do Sul and Itabapoana Hydrographic Region and, as well as several basin of fluminense hydrographic regions, presents a long history of anthropogenic interventions inside and outside channels. The objective of this present work is bringing forward mapping of the River Styles in the Macabu Basin to be applied in the management of water resources, considering the current dynamics of geomorphological and hydrogeomorphological processes. The mapping and the classification of river segments and their typologies were performed based on the application of morphometric parameters for the evaluation of regional and local controls on the river shape and behavior, valley confinement, river planform, channel length and valley bottom geomorphological units. The results show that the relief compartments allows the occurrence of different fluvial features, exerts regional control in the fluvial system and influences the valley characteristics. Thus, the spatial configuration of the compartments determines the patterns of behavior in each sector. Eight River Styles have been identified whose differentiation allows understanding how processes and forms are characterized, integrated and distributed within the river system. In general, Macabu Basin is a multiple and complex environment with many issues related to its uses and modifications. The results represent part of the inputs needed for efficient and effective management and decision-making.Keywords: Fluvial Geomorphoplogy; River Classification; Morphometric Index; Valley Setting.