george 'mathias Kondolf

University of California, Berkeley | UCB · Department of Landscape Architecture and Environmental Planning

Les « solutions fondées sur la nature » (SFN) ont été définies et promues à l’échelle internationale, et leur déploiement dans différents contextes institutionnels demeure encore peu étudié. Nous proposons dans cet article d’étudier la déclinaison de ce concept à différentes échelles, en France et aux États-Unis. Grâce à une recherche ancrée en sci...

For millennia humans have extracted biological and physical resources from the planet to sustain societies and enable the development of technology and infrastructure. Growth in the human population and changing consumption patterns have increased the human footprint on ecosystems and their biodiversity, including in fresh waters. Freshwater ecosys...

Historical information about floods is not commonly used in the US to inform land use planning decisions. Rather, the current approach to managing floods is based on static maps derived from computer simulations of the area inundated by floods of specified return intervals. These maps provide some information about flood hazard, but they do not ref...

This book gives positive examples how humans and rivers have been, and are still in some places, living in harmony. It analyses how this knowledge can be transferred into modern river management schemes and thereby it attempts to mitigate the deplorable trend of the decline of biological and cultural heritages and diversities in and along rivers. A...

Urban rivers deliver a broad range of contributions of nature to human development. The exploitation of the riverine ecosystem services evolves with uncertainty. In addition to the current decreasing of ecosystem health and changing climate, the impact of societal development on the river system directly reduces the potential delivery of future eco...

Hydropower continues to expand globally as the power sector transitions away from carbon-intensive fossil fuels. New dam sites vary widely in the magnitude of their adverse effects on natural ecosystems and human livelihoods. Here, we discuss how strategic planning of hydropower expansion can assist decision makers in comparing the benefits of buil...

Owing to only a few decades of human influence and unsustainable management of the Mekong River basin’s natural resources, the Mekong Delta is receding rapidly. Most of the delta landform, home to 17 million people and an economic powerhouse, could slip below sea level by 2100. Avoiding such a catastrophic impact will require concerted actions that...

Dams are essential to society, yet have tremendous environmental impacts, for which there is an increasing interest in mitigation. At the same time, sedimentation threatens the sustainability of reservoir storage and reservoir functions. We use the term dam renovation to encompass a wide range of measures, including dam rehabilitation, a term commo...

Conventional flood control has emphasized structural measures such as levees, reservoirs, and engineered channels—measures that typically simplify river channels and cut them off from their floodplain, both with adverse environmental consequences. Structural measures tend to be rigid and not easily adapted to increased flooding regimes resulting fr...

Predictions of urban runoff are heavily reliant on semi‐distributed models, which simulate runoff at subcatchment scales. These models often use “effective” model parameters that average across the small‐scale heterogeneity. Here we quantify the error in model prediction that arises when the optimal calibrated value of effective parameters changes...

Ecosystem management and governance of cross-scale dependent systems require integrating knowledge about ecological connectivity in its multiple forms and scales. Although scientists, managers, and policymakers are increasingly recognizing the importance of connectivity, governmental organizations may not be currently equipped to manage ecosystems...

Nous proposons dans ce guide une nouvelle approche méthodologique pour évaluer la pertinence et mettre en œuvre des « lâchers morphogènes » en aval de barrages. Ces lâchers correspondent à des débits relativement élevés lâchés par les barrages afin de générer des changements dans les caractéristiques physiques des lits fluviaux (ex., décolmatage, d...

In France, sirens have been the principal tool designated to alert the population in the case of danger. However, their efficacity has not been objectively tested. Using a geographical information system, questionnaires, and surveys, we analyzed (1) the spatial distribution of the siren network in relation to the covered population, the hazards thr...

Significance Globally, river deltas, which support some of the planet’s most productive agroeconomic systems and half a billion livelihoods, are at risk of being drowned by rising sea levels and accelerated subsidence. Whether delta land falls below sea level will depend on land and water management in the delta, sediment supply from the upstream b...

Although the hydrologic cycle is a continuously renewable resource, the natural rate of water delivery is highly variable. Water is made available to our society on a consistent and reliable basis largely due to flow regulation by storage reservoirs. However, under current management, the reservoir storage capacity needed for flow regulation is a n...

Process-based restoration of fluvial systems removes human constraints on nature to promote ecological recovery. By freeing natural processes, a resilient ecosystem may be restored with minimal corrective intervention. However, there is a lack of meaningful design criteria to allow designers to evaluate whether a project is likely to achieve proces...

Tackling climate change and human development challenges will require major global investments in renewable energy systems, including possibly into large hydropower. Despite well-known impacts of hydropower dams, most renewable energy assessments neither account for externalities of hydropower nor evaluate possible strategic alternatives. Here we d...

Sediment is an essential component of water and river systems. The anthropogenic alteration of sediment fluxes in the world’s rivers is one of the principal markers of the Anthropocene, the new geological epoch characterized by human influence at the planetary scale. In spite of its environmental and historical importance, water and river histories...

Le 9 janvier 2018, à Montecito (Comté de Santa-Barbara, État de Californie, États-Unis), de violentes coulées de débris sont apparues vers 4 h du matin, suite à une intensité pluviométrique remarquable (13 mm en 5 minutes, soit une intensité horaire de 157 mm/h). Ces coulées, constituées de blocs, de boue et de branches d'arbres, ont pu déposer, pa...

The Mekong River in Southeast Asia, one of the world’s great rivers, has been facing disruption of its sediment balance and resultant impacts on nutrient fluxes, aquatic ecology, floodplains and the delta. Using monitoring data from 1993 to 2018, we estimated the temporal variability of sediment loads in Tonle Sap and Lower Mekong Rivers in Cambodi...

Flushing flows are deliberate high-flow releases designed to mimic effects of floods in removing fine sediment from downstream aquatic habitats. A special case of environmental flows, flushing flows are intended to act on geomorphic processes to mitigate ecological effects of dams. We review definitions advanced for these flows, and then propose a...

Eco-tourism is a growing part of the tourism industry. However, there are no agreed-upon criteria of what constitutes eco-tourism, so the industry is currently self-identified, with eco-lodges simply declaring themselves so. Here we present the first systematic comparison of eco-tourism versus conventional (or mass) tourism, using as our study area...

Throughout the humid tropics, increased land disturbance and concomitant road construc- tion increases erosion and sediment delivery to rivers. Building road networks in developing countries is commonly a priority for international development funding based on anticipated socio-economic benefits. Yet the resulting erosion from roads, which recent s...

Recent studies have reported that connected impervious areas – those impervious surfaces that contribute directly to runoff in a storm network or stream – are a better indicator of hydrologic response, stream alteration, and water quality than total impervious area. However, most methods for quantifying connected impervious areas require major assu...

Nous proposons une nouvelle approche méthodologique pour évaluer la pertinence et mettre en œuvre des ≪ lâchers morphogènes » en aval de barrages hydroélectriques. Ces lâchers correspondent à des débits relativement élevés lâchés par les barrages afin de générer des changements dans les caractéristiques physiques des lits fluviaux (par exemple, déc...

Urban riverfront interventions are ubiquitous throughout the developed world, and increasingly also in the Global South. Many have failed spectacularly. We conducted a systematic review of failed riverfront interventions to draw lessons that could improve future projects. Learning from past mistakes may be more important than observing successes, b...

Anthropogenic impacts in large rivers are widely studied, but studies of recovery once a disturbance has stopped are uncommon. This study examines the biogeomorphic recovery of a 40‐km river corridor on the mid‐Apalachicola River, Florida following the cessation of dredging, disposal, and snag removal in 2002. This failed navigation project resulte...

Cairo is a congested city with high rate of urbanization and very limited public space. Cairo has one of the lowest rates of parkland per capita of any major city. Moreover, the banks of the Nile, formerly alive with activities such as washing, fishing, and felucca landings, were by the end of the twentieth century largely cutoff from free public a...

Abstract. This paper discusses the usefulness of keeping sirens to alert in an emergency situation likely to harm the physical integrity of property or the population in France. Sirens are the main pillars of the National Alert Network (NAN) deployed from 1954 to 2010, and these tools remain the basis of the future Population Alerting and Informati...

Aquatic biological communities have directly undergone human-induced changes. Altered hydrological and morphological processes in running waters have caused the degradation of main habitats for biotas and have disturbed ecosystem functionality. The latest advances in river restoration concerned the rise in far-reaching hydromorphological restoratio...

The transboundary Mekong Basin has been dubbed the “Battery of Southeast Asia” for its large hydropower potential. Development of hydropower dams in the six riparian countries proceeds without strategic analyses of dam impacts, e.g., reduced sediment delivery to the lower Mekong. This will impact some of the world’s largest freshwater fisheries and...

In many countries of the Global South, aquatic ecosystems such as streams, rivers, lakes, and wetlands are severely impacted by several simultaneous environmental stressors, associated with accelerated urban development, and extreme climate. However, this problem receives little attention. Applying a DPSIR approach (Drivers, Pressures, State, Impac...

River management based solely on physical science has proven to be unsustainable and unsuccessful, evidenced by the fact that the problems this approach intended to solve (e.g., flood hazards, water scarcity, and channel instability) have not been solved and long‐term deterioration in river environments has reduced the capacity of rivers to continu...

A strategic mix of solar, wind and storage technologies around river basins would be safer and cheaper than building large dams, argue Rafael J. P. Schmitt, Noah Kittner and colleagues. A strategic mix of solar, wind and storage technologies around river basins would be safer and cheaper than building large dams, argue Rafael J. P. Schmitt, Noah Ki...

Most environmental flow assessments (EFAs) are done for rivers below dams which trap sediment and change the flow regime downstream. Dams disrupt the flow of sediment and the capacity of the stream to convey sediment, with broadly predictable consequences for morphology and composition of the channel below the dam and on the biota that uses the cha...

This chapter recapitulates the main points, offers recommendations, provides brief comments on particular methods, and presents a checklist for environmental flow assessment (EFA). EFA is about predicting the uncertain ecological consequences of changes in the flow regime of a stream. The circumstances of EFAs vary too much for any list of specific...

The proper use of models requires a good understanding of the model, the data at hand, the thing being modeled, the questions being asked, and the reasons for the modeling. The use of models is ubiquitous in environmental flow assessment (EFA), so understanding the selection, implementation, and testing of models is important. The chapter summarize...

Environmental flows are flows in a river required to sustain aquatic ecosystems and other beneficial uses of free‐flowing rivers. Environmental flow assessment (EFA) are surprisingly difficult to do right, constrained by the natural variability of the environment through which rivers flow and the diverse needs of organisms that live there. This cha...

This chapter emphasizes the early period of environmental flow assessment (EFA), in the mid‐twentieth century. It also emphasizes California, since people are most familiar with developments here, and California was in the forefront of developing methods for EFA. EFA presupposes a way to act on the results, so a logical precursor to EFA is some way...

This chapter provides an approach to improve the use of existing knowledge in the ecological predictions of environmental flow assessments. The approach attempts to simultaneously maximize the value gained from evidence in the literature, knowledge of experts, and empirical data. Bayes' rule offers a halfway solution, retaining the influence of exp...

This chapter presents a basic and brief overview of temporal and spatial patterns of flow in streams, to provide background for thinking about environmental flows. It illustrates the range of flow regimes in natural and regulated rivers. Flow in streams results from precipitation. Precipitation patterns and their resulting runoff patterns vary wide...

Rivers and streams vary widely across the globe, from the Arctic to the tropics, and the mountains to the plains. The plants and animals adapted these systems vary widely as well. This chapter briefly reviews some basics of fish biology and stream ecology. It describes how river and streams are structured and adaptations of stream organisms in rela...

Methods of many different kinds have been developed for environmental flow assessment, as well as frameworks within which various methods are combined. Environmental flow methods can be classified in various ways. This chapter briefly describes Tharme's four general categories of methods: hydrological, hydraulic rating, habitat simulation and holis...

People conducting environmental flow assessments (EFAs) draw on a variety of intellectual tools, concepts and methods that have been developed mostly in science or engineering, ranging from simple graphics to classifications to complex computer models. This chapter briefly reviews various tools, methods, models, concepts, or approaches that are use...

In a 2010 review, Arthington et al. remarked that: “There is now wide recognition that a dynamic, variable water regime is required to maintain the native biodiversity and ecological processes characteristic of every river and wetland ecosystem. Yet it remains a challenge to translate this ‘natural flow regime’ paradigm into quantitative environme...

The Tonle Sap is the most fertile and diverse freshwater ecosystem in Southeast Asia, receiving nurturing water flows from the Mekong and its immediate basin. In addition to rapid development in the Tonle Sap basin, climate change may threaten natural flow patterns that sustain its diversity. The impacts of climate change on river flows in 11 sub-b...

San Francisco Bay, the largest estuary on the Pacific Coast of North America, is heavily encroached by a metropolitan region with over 7 million inhabitants. Urban development and infrastructure, much of which built over landfill and at the cost of former baylands, were placed at very low elevations. Sea level rise (SLR) poses a formidable challeng...

The sediment load of rivers is affected by human alterations, such as increased soil erosion due to removal of native vegetation, road construction, and other land disturbances, especially in steep upland areas (Figure 1). Sediment loads can also be increased by urbanization and the resulting increased runoff. As sediment loads are transported down...

The practice of enhancing existing rivers and creating entirely new waterscapes has exploded in China over the past two decades. In our study of 104 randomly selected cities across China, we identified 14 types of river projects based on grey literature reports and their appearance on sequential aerial imagery, falling into three categories: ‘engin...

San Francisco Bay, the largest estuary on the Pacific Coast of North America, is heavily encroached by a metropolitan region with over 7 million inhabitants. Urban development and infrastructure, much of which built over landfill and at the cost of former baylands, were placed at very low elevations. Sea-level rise (SLR) poses a formidable challeng...

Reservoirs play a critically important role in supplying water for human uses. However, sedimentation limits storage capabilities and increases risk for aging infrastructure. The objectives of this paper are to synthesize both general sediment management strategies and past sediment management efforts in Taiwan in order to identify the barriers to...

A poorly designed riverfront intervention typically fails on several levels: a bad program, with the wrong budget and timing, no concern for local needs or context, results in an unattractive and costly intervention, with reduced to no social or environmental benefit. Urban riverfront interventions may be improved in the future if, when deciding wh...

While not among the globe’s largest rivers in terms of discharge, the Rhine has assumed outsized importance due its role in history and as the spine of Western Europe, with an extraordinary concentration of population and industry, and consequently profound anthropic modifications. Floods have always plagued the Rhine, but twentieth-century correct...

As Denver, Colorado, began its rapid growth in the 1960s, two major floods led to the formation of an extensive flood control district, which adopted a two-pronged approach: Through land-use regulation, it prevented further development in floodplains. In already-built floodplain areas, it removed houses where possible and elsewhere used structural...

The Mississippi River was the first theater in which the federal government sought to control floods and improve navigation through the efforts of the US Army Corps of Engineers, initially under a “levees only” philosophy, later revised (after the disastrous 1927 flood) to include multiple approaches, such as backwater areas and flood bypasses. The...

The San Francisco and Lisbon estuaries share many geographical similarities, but their different governance makes for interesting comparisons. Many tributaries to San Francisco Bay were channelized by the US Army Corps in the 1950s–1970s. The design flaws of these projects (such as their having ignored sediment) are manifest as local governments no...

The past half century has seen an evolution in thinking from ‘flood control’ to ‘flood risk management’, recognizing that risk results from both hazard and vulnerability. Rather than rely only on engineering structures to reduce flood magnitude or extent, recent policies emphasize avoiding construction in flood-prone areas (or moving people from fl...

Dams in the Mekong Basin are mostly planned project-by-project and without strategic analysis of their cumulative impacts on river processes such as sediment connectivity. We analyse missed and future opportunities for reducing hydropower impacts on sediment connectivity through strategic planning of dams in the Se Kong, Se San and Sre Pok ('3S') t...

Conflicts between national and local governments over land use in floodplains have been well documented in the US and elsewhere. The US National Flood Insurance Program offers subsidized flood insurance to communities that agree to prevent further development in floodplains, but the requirements are poorly enforced and local governments are commonl...

Sedimentation is a major issue for water systems worldwide, but the need for sustainable sediment management is rarely addressed. This article surveys the problem of sedimentation in the contemporary sphere in addition to drawing on archaeological evidence of past unsustainable and sustainable sedimentation management practices. A compact character...

Two decades after the construction of the first major dam, the Mekong basin and its six riparian countries have seen rapid economic growth and development of the river system. Hydropower dams, aggregate mines, flood-control dykes, and groundwater-irrigated agriculture have all provided short-term economic benefits throughout the basin. However, it...

Sediment supply to rivers, subsequent fluvial transport, and the resulting connectivity on network-scales are often sparsely monitored and subject to major uncertainty. We propose to approach that uncertainty by adopting stochastic approaches for modeling network sediment connectivity. We present such a stochastic approach for modeling sand connect...

Dry Creek is a major tributary of the Russian River in Northern California (USA) that has experienced hydrologic and morphologic alterations after the closure of Warm Springs Dam in 1983. Our objective is to present a detailed diagnosis of the modification of the creek’s flow and sediment regimes, and interpret the alterations regarding the ecomorp...

Quantifying sediment trapping in hydropower cascades requires integrated sediment modeling at the scale of the entire river catchment. While catchment-scale processes are often poorly monitored and few hydro-dynamic numerical models are applicable on such scales, new global datasets from remote sensing and new modeling approaches can help us unders...

With changing climate and rising seas, proliferation of hydroelectric dams, instream sand mining, dyking of floodplains, accelerated subsidence from groundwater pumping, accelerated sea-level rise, and other anthropic impacts, it is certain that the Mekong Delta will undergo large changes in the coming decades. These changes will threaten the very...

The Apalachicola River, which begins at the confluence of the Chattahoochee and Flint rivers near the Georgia-Florida State line, has multiple human impacts. Water inputs declined due to upstream irrigation and urbanization in Georgia. Sediment trapped by numerous small to large dams, including construction of Jim Woodruff Dam in 1954 near the Apal...

Modeling the proliferation of hydrocarbon wells across a landscape using logistic regression against landscape variables is a novel approach with significant potential to inform regional planning. However, any modeling study should incorporate the most relevant controlling variables, and as much data as possible about both the phenomenon and the co...

The Lower Colorado River Multi‐Species Conservation Program (MSCP) is charged with restoring habitat for 26 species such as the southwestern willow flycatcher (Empidonax traillii extimus) impacted by water development projects on the river. As of 2015, the MSCP had spent $200 million to create 1,200 hectares of habitat at nine sites, but the benefi...

Two decades since calls for stream restoration projects to be scientifically assessed, most projects are still unevaluated, and conducted evaluations yield ambiguous results. Even after these decades of investigation, do we know how to define and measure success? We systematically reviewed 26 studies of stream restoration projects that used macroin...

The San Francisco Bay (CA, USA) and the Tagus Estuary (Lisbon, Portugal) share striking similarities in terms of morphology and urban development. A finer analysis of development patterns reveals crucial differences in the extent of shoreline alteration and types of land use that now encroach upon natural estuarine habitat. Through historical map a...