Flooding is a function of hydrologic, climatologic, and land use characteristics. However, the relative contribution of these factors to flood risk over the long-term is uncertain. In response to this knowledge gap, this study quantifies how urbanization and climatological trends influenced flooding in the greater Houston region during Hurricane Harvey. The region-characterized by extreme precipitation events, low topographic relief, and clay-dominated soils-is naturally flood prone, but it is also one of the fastest growing urban areas in the United States. This rapid growth has contributed to increased runoff volumes and rates in areas where anthropogenic climate changes has also been shown to be contributing to extreme precipitation. To disentangle the relative contributions of urban development and climatic changes on flooding during Hurricane Harvey, we simulate catchment response using a spatially-distributed hydrologic model under 1900 and 2017 conditions. This approach provides insight into how timing, volume, and peak discharge in response to Harvey-like events have evolved over more than a century. Results suggest that over the past century, urban development and climate change have had a large impact on peak discharge at stream gauges in the Houston region, where development alone has increased peak discharges by 54% (±28%) and climate change has increased peak discharge by about 20% (±3%). When combined, urban development and climate change nearly doubled peak discharge (84% ±35%) in the Houston area during Harvey compared to a similar event in 1900, suggesting that land use change has magnified the effects of climate change on catchment response. The findings support a precautionary approach to flood risk management that explicitly considers how current land use decisions may impact future conditions under varying climate trends, particularly in low-lying coastal cities.
Planning of traditional coastal flood risk management strategies are largely predicated on storm surge protection against extreme hurricanes, i.e. storm surge. However, (1) hurricane storm surge and (2) hurricane rainfall-runoff are not mutually exclusive flood hazards. Little research has emphasized the need for quantifying and characterizing the joint hydraulic processes between hurricane storm surge and rainfall-runoff during real events for enhancing effective flood risk mitigation. In this regard, an improved hydrological and hydrodynamic modeling framework has been developed for the Houston Ship Channel (HSC) and Galveston Bayto serve as a quantitative testbed for evaluating coupled hurricane storm surge and rainfall-runoff.
Core Ideas
Resistivity imaging revealed dynamic subsurface response to drought across an ecotone.
Resistivity responses restricted to rooting zones of vegetation type on each slope.
Drought led to a deepening of interpreted soil moisture losses.
Rewetting after drought did not immediately return to pre‐drought conditions.
This study investigated the spatial distribution and seasonal variation of soil moisture during a drought year throughout a first‐order drainage basin whose hillslopes have different vegetation and soil. The north‐facing slope has juniper trees [Juniperus monosperma (Engelm.) Sarg.] and finer soil textures, while the south‐facing slope has creosote bushes [Larrea tridentata (DC.) Coville]. Time‐lapse, two‐dimensional electrical resistivity measurements, which can detect changes due to soil moisture, were conducted to capture subsurface moisture changes across the ecotone, from one hillslope to the other and along the ecotone down the valley axis. After the onset of the drought, the upper 3 m of the entire hillslope was mostly drying (resistivity was increasing). As the drought progressed and when there was less available shallow soil moisture, the resistivity profiles suggested that both juniper and creosote bushes sequestered moisture stored from increasingly greater depths, eventually reaching their respective average maximum rooting depths of ∼6 m for juniper and ∼3 m for creosote. However, this was also accompanied by decreases in resistivity (increases in soil moisture) at shallower depths, suggesting hydraulic redistribution. With shallow rewetting of the hillslope following storm events near the end of the study period, shallow areas could once again support vegetation on both hillslopes. Electrical resistivity imaging is effective for studying the spatiotemporal dynamics of soil moisture throughout the critical zone in response to water stress and can be used to inform ecohydrologic connections.
As demand grows for climate change projections at landscape scales, stakeholders, energy and water managers, and policymakers alike are relying increasingly on downscaled output from global climate models (GCMs) to anticipate, adapt to, and understand climate change impacts. Historical reanalyses are often downscaled to serve as references to assess downscaled GCM fidelity (
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