A simple method for designing infiltration low impact development techniques considering effects of urbanization and climate change

Método simplificado de dimensionamento de técnicas de drenagem de baixo impacto baseadas em infiltração considerando efeitos de urbanização e mudanças climáticas

ABSTRACT

Infiltration-based low-impact development (LID) techniques are widely used to reduce peak runoff and enhance groundwater recharge in urban catchments. Their effective design requires selecting an appropriate surface area and maximum ponding depth to ensure sufficient storage volume. However, arbitrary assumptions about the ponding depth can lead to over- or undersizing. This paper introduces MoDOBR, a spreadsheet-based optimization model for designing infiltration basins that accounts for clogging scenarios and variable soil conditions. The model dynamically couples surface water balance with subsurface infiltration using a simplified Green-Ampt formulation. Four numerical examples are presented, including a sensitivity analysis across different soil textures. Results demonstrate that assuming a constant infiltration rate equivalent to the saturated hydraulic conductivity significantly underestimate infiltration dynamics and leads to overdesign basins. In contrast, variability in initial soil moisture conditions has a relatively minor impact on design outcomes. The analysis further reveals that optimal height-area coupling is essential, particularly in low-permeability soils, where the integration of underdrains enables feasible and hydraulically compliant designs. For a 5-year return period event, the required basin area ranges from 2.9% of the catchment for sandy soils to over 50% for clayey soils in the absence of drainage infrastructure.

Keywords:
Design of Retention Ponds; Pre-development; Optimization of Retention Ponds; Low Impact Development