ABSTRACT:

This resource archives Model files supporting the paper "Impacts of climate change on storm event based flow regime and channel stability of urban headwater streams".
The abstract for this paper follows: "Due to the recent improved availability of global and regional climate change (CC) models and associated data, the projected impact of CC on urban stormwater management is well documented. However, most studies are based on simplified design storm analysis and unit-area runoff models but studies on evaluation of long-term, continuous hydrologic response of extensive stormwater control measures (SCM) implementation under future CC scenarios are limited. Moreover, channel stability in response to CC is seldom evaluated due to the challenge associated with developing a long term, continuous sediment transport model. The study objective was to evaluate the impact of CC on storm event based flow regime and channel stability in a small, urbanized catchment (0.9 km2) in Montgomery County, Maryland, USA. This study employed a previously developed well-calibrated, coupled hierarchical modeling approach, integrating a watershed-scale Storm Water Management Model (SWMM) with the Hydrologic Engineering Centers River Analysis System (HEC-RAS) to achieve its goal. Ensemble modeling results indicates that conclusions related to CC impacts of SCM induced flow drawn from simplified, unit area models are very much different from dynamic, continuous simulations that consider the complexities of real urban catchments and SCM interactions. Despite a general decrease in total rainfall amount for most storm events, there is a noted increase in intensity for nearly all future storm events compared to current climatic conditions. This change in storm event-based rainfall pattern is expected to drive the catchment scale hydrology to a flashier regime in future which in turn is expected to increase the extent of channel erosion compared to the current climate condition. A multicriteria design approach considering the interplay of multiple SCMs and local sediment transport capacity is thus necessary to ensure channel stability under changing climate."

ABSTRACT:

This resource archives Model files supporting the paper "Effectiveness of Stormwater Control Measures in Protecting Stream Channel Stability".
The abstract for this paper follows: "While research on the hydrologic impact of different types of stormwater control measures (SCMs) is extensive, little research exists linking urbanization, widespread implementation of SCMs, and channel stability in headwater streams. This study evaluated whether the Unified Stormwater Sizing Criteria (USSC) regulations in the state of Maryland, USA, which require the use of both end-of-pipe and distributed, small-scale SCMs, protect channel stability. To achieve this goal, a coupled hierarchical modeling approach utilizing the Storm Water Management Model (SWMM) and the Hydrologic Engineering Center River Analysis System 6.3 (HEC-RAS) was developed to predict changes in streamflow and sediment transport dynamics in a first-order gravel-bed, riffle-pool channel. Storm event discretization revealed that 88% of observed storm events during the 16 years (2004-2020) had durations less than 18 hours and that the greatest peak flows resulted from storm events with durations less than 24 hours. HEC-RAS simulation results also showed that both channel degradation and aggradation, as high as 1.2 m, will likely occur regardless of the combination of SCMs employed in the catchment. Overall, this study provides valuable insights into the complex interactions between SWM practices, flow regimes, and sediment transport dynamics in heavily urbanized watersheds. It is recommended that SCMs be designed using a continuous simulation model with at least 10 years of continuous rainfall data. Furthermore, to protect channel stability, the SCM design goal should focus on maintaining pre-development sediment transport regimes across a range of flows."