Effectiveness of Design and Implementation Alternatives for Stormwater Control Measures Modeled at the Watershed...

Area of Science:

• Environmental Engineering
• Hydrology
• Urban Planning

Background:

• Evaluating stormwater control measures (SCMs) effectiveness requires understanding groundwater-surface water interactions.
• These interactions impact streamflow, channel geomorphology, and aquatic ecosystems in urban watersheds.

Purpose of the Study:

• To assess the impact of different SCM designs and implementation strategies on streamflow exceedance levels and volumes.
• To evaluate SCM effectiveness at the watershed scale for improving hydrologic responses.

Main Methods:

• A process-based block-connector model of Sligo Creek, a 29 km² urban watershed, was developed and calibrated.
• Simulations included three SCM unit designs (pond, infiltration, infiltration with underdrain) and three implementation levels (10%, 50%, 90% impervious area diversion).
• Flow exceedance probability curves were used to compare model simulations against predevelopment conditions.

Main Results:

• A minimum of 50% impervious area retrofit is necessary to approximate predevelopment base and peak flows.
• Infiltration SCMs with underdrains showed the closest performance for intermediate flow ranges.
• Concentrating SCMs in the lower watershed was more effective than uniform implementation for meeting predevelopment flow curves.

Conclusions:

• SCM design and placement significantly influence watershed-scale hydrologic outcomes.
• Targeted implementation of effective SCMs, particularly infiltration types, can help restore urban streamflow regimes.
• Findings inform planning decisions for SCM retrofits in developed watersheds.