Evaluation of infiltration efficiencies in vegetated swales through SWMM and single ring infiltrometer tests: - A numerical and field experimental study
Translated title
Evaluering af infiltrationseffektivitet i trug ved brug af SWMM og enkelt-rings infiltrometer tests
Authors
Godskesen, Mathias Åbo ; Arberg, Alex
Term
4. term
Publication year
2022
Pages
99
Abstract
This thesis examines how effectively swales (shallow, trough-like channels used in local stormwater management) infiltrate rainwater. Swales are often used alongside other systems such as detention or infiltration basins. In current Danish practice, infiltration along the swale is rarely included when sizing these systems, even though swales are often built with a longitudinal slope. To investigate this, field tests were carried out with a single-ring infiltrometer, which measures how quickly water infiltrates the soil. The measurements were used as input to numerical models in SWMM (Storm Water Management Model). Both historical rainfall and synthetic design storms were simulated. The models used Horton’s infiltration equation and were applied to a general setup as well as to the specific test locations. The results show that swales handle everyday rainfall well: the share of rain that infiltrated was 42% at Marshalls Allé and 52% at Skjoldet in the historical record. In contrast, performance was low for short, very intense design storms: 6.6–7.4% at Marshalls Allé for a 10-year, 10-minute event, and 8.6–10.9% at Skjoldet for a 100-year, 10-minute event. The analysis also indicates that using Horton’s equation and accounting for the swale’s longitudinal slope affect overall infiltration efficiency. Based on these findings, the authors recommend reconsidering current Danish sizing practice.
Dette speciale undersøger, hvor effektivt trug – lavvandede, aflange render i Lokal Afledning af Regnvand (LAR) – kan få regnvand til at sive ned i jorden. Trug bruges ofte sammen med andre LAR-anlæg som forsinkelses- eller nedsivningsbassiner. I dansk praksis medregnes infiltrationen langs truget sjældent, når anlæggene dimensioneres, selvom trug ofte anlægges med længdefald. For at belyse dette blev der udført feltforsøg med et enkeltrings infiltrometer, som måler, hvor hurtigt vand trænger ned i jorden. Måleresultaterne blev brugt som input i numeriske modeller i programmet SWMM (Storm Water Management Model). Der blev simuleret både historiske regnhændelser og syntetiske designregn. I modellerne indgik Hortons infiltrationsligning, og der blev både set på et generelt model-setup og på de konkrete testlokationer. Resultaterne viser, at trug er effektive til at håndtere hverdagsregn: andelen af regn, der infiltrerede, var 42% ved Marshalls Allé og 52% ved Skjoldet i den historiske regnserie. Til gengæld var effektiviteten lav ved korte, meget intense designregn: 6,6–7,4% ved Marshalls Allé for en 10-års, 10-minutters hændelse og 8,6–10,9% ved Skjoldet for en 100-års, 10-minutters hændelse. Analysen peger også på, at både valg af Hortons infiltrationsligning og trugets længdefald påvirker den samlede infiltrationseffektivitet. På den baggrund foreslår forfatterne, at den nuværende danske dimensioneringspraksis bør revurderes.
[This apstract has been rewritten with the help of AI based on the project's original abstract]