## 1 Introduction  
Runoff management has become a key topic in water management in recent times, particularly in the context of urban water drainage, flood management and climate change adaptation [1, 2, 3, 4, 5]. Runoff processes determine how much precipitation becomes surface runoff. It is a key hydrological process, and its relevance is emphasised due to the extent to which human activities can alter this process. In both rural and urban areas, land use drastically changes runoff processes [6, 7, 8]. Different areas and ecosystems experience different issues regarding runoff processes, which can be globally driven. Climate change and rapid urbanisation are expected to exacerbate the potential negative impacts of runoff [4, 5, 9]. Extreme storm events are projected to become more frequent and severe [10, 11]. The continuous expansion of urban areas leads to greater areas of impermeability [3, 5]. Flooding due to sealed surfaces related to urbanisation is present in many built-up areas worldwide [3, 12, 13]. Often, the flood risk in these areas comes from extreme storm events, where high-intensity precipitation events result in water not being able to infiltrate or drain away. This causes high peak discharges in urbanised sub-catchments. Understanding the behaviour of runoff can help reduce flood risk in these areas and plan possible mitigation measures. In many cases of runoff management, nature-based solutions (NbS) are frequently being proposed [2; 14; 15; 16; 17]. NbS are often preferred to grey infrastructure in environmentally sensitive areas. They help provide cooling, fresh air and a better ambience for locals compared to grey infrastructure [18]. Additionally, NbS typically provide much better infiltration, which can help build drought resilience and maintain ecosystems [19]. Many issues arising from changes in runoff processes come from human activity. NbS aim to mimic natural processes and are being introduced in many cities around the world [20]. They help decrease surface runoff by increasing infiltration, which can benefit groundwater recharge and help maintain environmental flows in dry periods [2; 20]. Common examples of NbS include bioswales, permeable paving, green roofs and infiltration trenches [21; 22; 23; 24]. NbS hold great promise, but it is important to quantify the changes in runoff that their implementation would provide. This type of analysis is significant both for the engineers tasked with designing such solutions and for the stakeholders who are involved in such projects. Hydrological modelling is a key tool for quantifying runoff changes under different scenarios. As sustainable runoff management becomes increasingly crucial, runoff modelling is being utilised to gain a deeper understanding of the factors influencing runoff and to predict how changes in a watershed affect these processes, as well as predicting the impact of runoff reduction mitigation measures. The modelling of NbS is an emerging topic, and therefore, the performance of NbS in different contexts is not fully understood [25; 26; 27]. The evaluation of NbS performance under extreme events in particular can be developed further [28; 29]. Different storms can have unique hydrological responses based on their intensity and duration [30; 31; 32]. The infiltration methods used in modelling often fail to account for this, leading to inaccuracies [33]. When using the SCS-CN method [34], tailoring the CN values to reflect these characteristics may allow for a better representation of the runoff response and improve model accuracy [35]. New models have been developed for specific cases, and NbS projects have been modelled using pre-existing models. For example, MIKE-SHE can be used for modelling some NbS, such as implementing trees and green roofs [2]. SWMM is commonly used due to its specific modules for NbS modelling, referred to as low-impact developments (LIDs) [14; 36; 37]. Various NbS have been modelled using HEC-HMS, including rainwater harvesting [38], retention ponds [39], bioswales [40] and changes in land use [39; 40].