Abstract. This paper uses a coupled hydrodynamic agent-based model (HABM) to investigate the effect of direct or indirect warnings in flood incident response. This model uses the LISFLOOD-FP hydrodynamic model and the NetLogo agent-based framework and is applied to the 2005 flood event in Carlisle, UK. The hydrodynamic model provides a realistic simulation of detailed flood dynamics through the event, whilst the agent-based model component enables simulation and analysis of the complex, in-event social response. NetLogo enables alternative probabilistic daily routine and agent choice scenarios for the individuals of Carlisle to be simulated in a coupled fashion with the flood inundation. Specifically, experiments are conducted using a novel “enhanced social modelling component” based on the Bass diffusion model. From the analysis of these simulations, management stress points (predictable or otherwise) can be presented to those responsible for hazard management and post-event recovery. The results within this paper suggest that these stress points can be present, or amplified, due to a lack of preparedness or a lack of phased evacuation measures. Furthermore, the methods outlined here have the potential for application elsewhere to reduce the complexity and improve the effectiveness of flood incident management. The paper demonstrates the influence that emergent properties have on systematic vulnerability and risk from natural hazards in coupled socio-environmental systems.

Using modified UK Environment Agency Flood Estimation Handbook techniques, inundation extent and likely flood hydrographs for 0.1% probability annual return periods are compared for twelve Roman town sites in the UK, both at the present day and for simulated Roman catchment conditions. Eight of the study sites appear to have suffered minimal urban flood liability as occupied in the Roman period. The exceptions were Canterbury, York, Leicester, and Chichester. It is reasonable to expect flood characteristics to have changed subsequently in response to transformations in catchment land use, urban expansion, wetland reclamation, and floodway engineering. However, modelling results suggest limited differences in flood flows attributable to such factors. Greater present-day urban damage liability essentially results from floodplain urban extension. There are also contrasts between sites: those Roman towns lying on floodplains themselves, rather than on slightly elevated terraces (Canterbury, Chichester), are dominated by groundwater regimes with attenuated flood peaks. Taken together, these results suggest some Roman awareness of the actualities of urban flood liability at the time. Site sensitivity has not been carried forward as urban expansion has flourished, especially from the nineteenth century with suburban and industrial expansion. The straightforward mapping approach here suggested should in future take account of multiple century-scale hydroclimatic changes, morphological river channel and floodplain transformations over similar time periods, and on-going improvements to inundation modelling.

Abstract. This paper presents a new flood risk behaviour model developed using a coupled Hydrodynamic Agent-Based Model (HABM). This model uses the LISFLOOD-FP Hydrodynamic Model and the NetLogo (NL) agent-based framework and is applied to the 2005 flood event in Carlisle, UK. The hydrodynamic model provides a realistic simulation of detailed flood dynamics through the event whilst the agent-based model component enables simulation and analysis of the complex, in-event social response. NetLogo enables alternative probabilistic daily routine and agent choice scenarios for the individuals of Carlisle to be simulated in a coupled fashion with the flood inundation. Experiments are also conducted using a novel, enhanced social modelling component, comprised of the Bass Diffusion Model, to investigate the effect of direct or indirect warnings in flood incident response. From the analysis of these coupled simulations, management stress points, predictable or otherwise, can be presented to those responsible for hazard management and post-event recovery. The results within this paper suggest that these stress points can be present, or amplified, by a lack of preparedness or a lack of phased evacuation measures. Furthermore, the methods here outlined have the potential for application elsewhere to reduce the complexity and improve the effectiveness of flood incident management. The paper demonstrates the influence that emergent properties have on systematic vulnerability and risk from natural hazards in coupled socio-environmental systems.

The authors would like to extend their sincere thanks to the referee for their time and considered thoughts on the submission. All comments and corrections have been thoroughly considered, with our respective action and/or response to these outlined below. General comments: This paper recognises the complexity of hazard situations and responses, but also that adaptive actions overall may be simulated from individual or 'agent' behaviours through using agent-based models (ABMs). On the physical side, hydrodynamic behaviour can have an equivalent concern for the local through detailed topographic modelling and C1 NHESSD Interactive comment

<p>Dissemination of early warning information and effective preparedness are critical components in flood risk management and shape the dynamics of any successful early response. To enable efficient preparedness and an early response to hazards, early warning information should be simple, usable, and deployed through trusted sources.</p><p>Successful management of floods are therefore dependent on clear and systematic communication structures which are, in turn, necessary to enable dissemination of such information. However, in many parts of Africa, flood event response is hampered by a lack of information on the inundation and potential exposure, with most large-scale systems limited to river flow forecasting, while local systems may lack coverage.</p><p>In collaboration with the UK Foreign and Commonwealth Office, we have previously developed a method for fluvial flood inundation and exposure forecasting that combines hydrological forecasts from the Global Flood awareness systems (GLOFAS) with the LISFLOOD-FP global flood model. This was deployed in Mozambique to provide probabilistic inundation maps and exposure estimates to assist humanitarian response for cyclones Idai, Kenneth and Eloise.</p><p>In this work, the flood models built with globally available datasets, and models augmented with local information, were evaluated for a series of uses and cases. Specifically, the 2020 fluvial flood event in the Nzoia basin in Kenya, the 2019 tropical cyclone flooding in Mozambique from cyclone Idai and recent pluvial flooding in the Zambian city of Lusaka.</p><p>We discuss the potential and limitations of such information to inform efficient action and build resilient futures via co-production of forecasts in Kenya and the community learning lab component of the FRACTAL+ initiative in Lusaka.</p>