Beth Tellman

Quantifying the impacts of land use change on flooding in data-poor watersheds in El Salvador with community-based model calibration

Abstract Urbanization can decrease the flood mitigation capacity of a catchment, and these impacts can be measured with hydrologic modeling. Models are typically calibrated against observed discharge and satellite data, but in a developing country context like El Salvador, these data are often unavailable. Even if a model is well calibrated and tested, its ability to influence land use plans requires additional stakeholder engagement. This study uses a participatory modeling approach to calibrate a watershed model and estimate flood impacts of land use scenarios in two urbanizing catchments in El Salvador with a linked land use–catchment hydrology–hydraulic model calibrated on flood height observed by community members. This paper explores both the value of household flood observation in model calibration and differences of flood extent estimates for land use scenarios with an uncalibrated versus community-calibrated model. We find that calibration using household surveys improves model performance. Results of scenario modeling suggest that while past urbanization has significantly increased household flood exposure in one catchment, future land use scenarios that further urbanize or reforest large areas of either catchment have little effect on the number of houses at risk for flooding. The success of the participatory methodology to increase model accuracy and link results to local land use planning makes clear the contribution of social science to traditional hydrological methods to understand land use–flood links in data-poor catchments.

Without inclusion, diversity initiatives may not be enough

Focus on minority experiences in STEM, not just numbers Diversity among scientists can foster better science (1, 2), yet engaging and retaining a diversity of students and researchers in science has been difficult (3). Actions that promote diversity are well defined (4), organizations are increasingly focused on diversity (5), and many institutions are developing initiatives to recruit and enroll students from underrepresented minority (URM) groups (racial, ethnic, gender, sexual identity, or persons with disabilities). Yet representation of URM groups in science, technology, engineering, and math (STEM) fields lag behind demographics in society at large (3–5), and many URM students feel unwelcome in academic departments and in scientific fields. Why is progress so limited (6, 7)? We see a widespread and under-acknowledged disconnect between initiatives aimed at increasing diversity in academic and professional institutions and the experience of URM students (including many of us authors) (6, 7). We argue that failure to grasp foundations of this disconnect is the crux of why diversity initiatives fail to reach the students that they were made to recruit. We believe that addressing this will resonate with other individuals and groups and help advance discussion in the scientific community.

Adaptive pathways and coupled infrastructure: seven centuries of adaptation to water risk and the production of vulnerability in Mexico City

Infrastructure development is central to the processes that abate and produce vulnerabilities in cities. Urban actors, especially those with power and authority, perceive and interpret vulnerability and decide when and how to adapt. When city managers use infrastructure to reduce urban risk in the complex, interconnected city system, new fragilities are introduced because of inherent system feedbacks. We trace the interactions between system dynamics and decision-making processes over 700 years of Mexico City’s adaptations to water risks, focusing on the decision cycles of public infrastructure providers (in this case, government authorities). We bring together two lenses in examining this history: robustness-vulnerability trade-offs to explain the evolution of systemic risk dynamics mediated by feedback control, and adaptation pathways to focus on the evolution of decision cycles that motivate significant infrastructure investments. Drawing from historical accounts, archeological evidence, and original research on water, engineering, and cultural history, we examine adaptation pathways of humans settlement, water supply, and flood risk. Mexico City’s history reveals insights that expand the theory of coupled infrastructure and lessons salient to contemporary urban risk management: (1) adapting by spatially externalizing risks can backfire: as cities expand, such risks become endogenous; (2) over time, adaptation pathways initiated to address specific risks may begin to intersect, creating complex trade-offs in risk management; and (3) city authorities are agents of risk production: even in the face of new exogenous risks (climate change), acknowledging and managing risks produced endogenously may prove more adaptive. History demonstrates that the very best solutions today may present critical challenges for tomorrow, and that collectively people have far more agency in and influence over the complex systems we live in than is often acknowledged.