Linking critical infrastructure resilience to social vulnerability through minimum supply concepts: review of gaps and development of an integrative framework

Increased attention has lately been given to the resilience of critical infrastructure in the context of natural hazards and disasters. 10 The major focus therein is on the sensitivity of critical infrastructure technologies and their management contingencies. However, strikingly little attention has been given to assessing and mitigating social vulnerabilities towards the failure of critical infrastructure and to the development, design and implementation of minimum supply standards in situations of major infrastructure failure. Addressing this gap and contributing to a more integrative perspective on critical infrastructure resilience is the objective of this paper. It asks which role social vulnerability assessments and minimum supply considerations can, 15 should and do – or do not – play for the management and governance of critical infrastructure failure. In its first part, the paper provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding of social vulnerabilities towards disaster-related infrastructure failures. Special attention is given to the current state of minimum supply concepts with a regional focus on policies in Germany and the EU. In its second part, the paper then responds to the identified gaps by developing a heuristic model on the linkages of critical infrastructure management, social 20 vulnerability and minimum supply. This framework helps to inform a vision of a future research agenda, which is presented in the paper’s third part. Overall, the analysis suggests that the assessment of socially differentiated vulnerabilities towards critical infrastructure failure needs to be undertaken more stringently to inform the scientifically and politically difficult debate about minimum supply standards and the shared responsibilities for securing them. Increased attention has lately been given to, first, social vulnerability reduction and, second, critical infrastructure management 25 in the context of natural hazards and disasters. However, strikingly little efforts have been made in linking the two in a coherent manner conceptually and practically. Addressing this gap is the objective of this paper. In its first part, it provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding of social vulnerability towards failures during and after disasters. Special attention is given to the current state of minimum supply concepts. In its second part, the paper then responds to the identified gaps by developing a novel conceptual framework on the 30 linkages of critical infrastructure management, social vulnerability and minimum supply. The framework is meant to guide future research as well as policy making and practical action. It facilitates and guides the conceptualization of (i) causal

The major focus therein is on the sensitivity of critical infrastructure technologies and their management contingencies.
However, strikingly little attention has been given to assessing and mitigating social vulnerabilities towards the failure of critical infrastructure and to the development, design and implementation of minimum supply standards in situations of major infrastructure failure. Addressing this gap and contributing to a more integrative perspective on critical infrastructure resilience is the objective of this paper. It asks which role social vulnerability assessments and minimum supply considerations can, 15 should and door do notplay for the management and governance of critical infrastructure failure. In its first part, the paper provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding of social vulnerabilities towards disaster-related infrastructure failures. Special attention is given to the current state of minimum supply concepts with a regional focus on policies in Germany and the EU. In its second part, the paper then responds to the identified gaps by developing a heuristic model on the linkages of critical infrastructure management, social 20 vulnerability and minimum supply. This framework helps to inform a vision of a future research agenda, which is presented in the paper's third part. Overall, the analysis suggests that the assessment of socially differentiated vulnerabilities towards critical infrastructure failure needs to be undertaken more stringently to inform the scientifically and politically difficult debate about minimum supply standards and the shared responsibilities for securing them.
Increased attention has lately been given to, first, social vulnerability reduction and, second, critical infrastructure management 25 in the context of natural hazards and disasters. However, strikingly little efforts have been made in linking the two in a coherent manner conceptually and practically. Addressing this gap is the objective of this paper. In its first part, it provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding of social vulnerability towards failures during and after disasters. Special attention is given to the current state of minimum supply concepts. In its second part, the paper then responds to the identified gaps by developing a novel conceptual framework on the 30 linkages of critical infrastructure management, social vulnerability and minimum supply. The framework is meant to guide future research as well as policy making and practical action. It facilitates and guides the conceptualization of (i) causal relationships between these three components, (ii) the assessment of system states in each component and (iii) the normative and political choices that need to be made explicit and tackled for turning the concept into policy and action. The paper closes by sketching out recommendations for a future research and practice agenda to close the detected gaps.

Introduction: Why the integration of critical infrastructure, social vulnerability and minimum supply matters
Critical infrastructure plays a key role in shaping a society's vulnerability towards natural hazards and the resulting risk of 5 disasters (cf. Grubesic & Matisziw 2013, Pescaroli & Alexander 2016. Infrastructure for electricity, water, transport, health and law enforcement, for example, plays a critical role for the day-to-day functioning of a society. Yet the importance of such infrastructure becomes particularly evident in situations of disasters and crises, when critical infrastructure is prone to fail, thereby causing wider impacts on the society. The vulnerability and/or resilience of critical infrastructure itself is therefore increasingly moving into the focus scientists, risk practitioners and political decision-makers (cf. Critical 5 2014, 10 2015, Herzog & Roth 2014, McGee et al. 2015. This attention is further driven by the growing role of critical infrastructure resulting from the rising societal dependence on technology, the ever-growing connectedness of infrastructure systems in the age of information technology and the growing global connectedness of people, production, trade and communication , Miles 2015. However, while increasing attention has lately been given to assessing the exposure and sensitivity of critical infrastructures 15 and the crises contingencies in their management (e.g. through so-called stress tests of nuclear power plants in the European Union following the Fukushima disaster), it remains highly questionable whether such a focus sufficiently captures the wider linkages between critical infrastructure failure and social vulnerability in a society at large. Anecdotal evidence and structured expert dialogues 1 suggest that risk in relation to critical infrastructure failure is currently captured in rather narrow and technocratic ways, focusing largely on technical parameters of individual infrastructure branches (e.g. water supply or power 20 generation) whilst failing to sufficiently capture the wider effects of critical infrastructure failure on societal risk and risk cascades (e.g. disruption in water supply due to electricity black-outs or a standstill of public transportation due to disruptions in ICT technology). Most importantly, however, it seems that the technical discourse on critical infrastructure failure does not adequately link into the domain of social vulnerabilities. It is not well understood which differential impacts critical infrastructure failure will have on different parts of the society (e.g. different age groups, neighborhoods, people with special 25 need for care) and how these differential impact patterns relate to different hazard and crises scenarios (e.g. a power black-out during a summer heatwave, affecting the potential for air conditioning and water supply, versus a flood-induced black-out during autumn or winter, taking effect on issues such as electric heating).
Social vulnerability studies provide powerful analytical lenses to approach such questions. Vulnerability thinking is, at its course, tailored to bring together (hypothetical) hazard scenarios with the societal predispositions for suffering harm when affected by such hazards (Blaikie et al. 1994). One of the core interests in vulnerability studies has therefore always been to 5 ask whether and how hazards and crises (such as a compound flood-cum-blackout hazard) take differentiated effects on different groups within society.
For the management of critical infrastructure failure, the vulnerability perspective also begs important scientific, normative and political questions with respect to the linkages between critical infrastructure failure, social vulnerability and minimum supply: Which levels of minimum supply (e.g. of electricity and water) are needed to avoid disastrous effects of natural-hazard-10 induced infrastructure failure? How are these minimum supply requirements perceived to differ between social groups (e.g. single elderly vs. family households or rich vs. poor neighborhoods) as well as between different other infrastructure elements (e.g. hospitals vs. water treatment plants vs. shopping malls)? Who ought to be responsible for securing a level of minimum supply (e.g. state authorities vs. private households)? Such debates are far from being at the core of ongoing discourses, posing serious questions about preparedness. One example is the 2016 German Civil Defense Plan requiring Germans to stockpile 15 private supplies. Instead of being taken serious the plan rather caused ridicules, indicating an overreliance in continuous infrastructure provision, making the German case particularly interesting to look at.
Against this background, the paper sets out examines the problematic nexus of critical infrastructure failure, social vulnerability and minimum supply. It has two main objectives: First it aims at exploring the current state-of-art regarding the scientific understanding and practical / political approaches on this nexus. This analysis is driven by a comprehensive review of academic 20 literature as well as policy and planning documents in the most relevant communities of practice. Second, and building on the gaps identified in the first part, the paper develops and novel conceptual framework that is argued to help structure emerging questions and future agendas of scientists, risk practitioners and political decision-makers concerned with limiting the social effects of critical infrastructure failure.
The next section of the paper will present the methods and result of the global literature review. The third section will develop 25 and present the proposed conceptual framing of the nexus between critical infrastructure (CI) failure, social vulnerability and minimum supply. The fourth section discusses resulting gaps in research and practice. The last section draws key conclusions.

Methodology: Data sources and methods of analysis
In order to get a more detailed understanding of how science, practice and policy has been dealing with the intersection of critical infrastructure management, social vulnerability reduction and minimum supply, we conducted a comprehensive 30 literature and document review. It covered three main fields of information: First, we reviewed scientific literature. A structured document search was conducted in the Scopus database in July 2017, which captures a wide range of academic literature, including most of the peer-reviewed journal articles, book chapters and proceedings of internationally important conferences.
We applied different key word searches in order to identify relevant contributions. Figure1 provides an overview over the search combinations and respective results. In a second step, we did a content analysis of the abstracts of the resulting documents in order to group the contributions into three groups: explicitly relevant (i.e. i.e. talk them).contributions that explicitly talk the linkages between CI failure and/or social vulnerability and/or minimum supply), implicitly relevant (i.e. 5 contributions which to not primarily target these linkages, e.g. in their titles and objectives, but nevertheless address them indirectly or as a side product or in the description of a certain disaster event) and not relevant (i.e. contributions shortlisted by the keyword search but not making relevant statements to the nexus of interest here). In cases where the abstracts did not allow for a clear allocation, we analyzed the entire article. Overall as little as fifteen papers were found directly linked to the core topic of this paper, while another 79 provided implicit information. 10 The second body of data captured in the analysis is composed of legal, policy and practice documents, published by national or international authorities and organizations. Identified by strategic google-searches and snowball-sampling from other sources, the final set of data analyzed in this group contained 73 documents, with over 4,500 pages in total. Different from the first body of scientific literature, focus of these documents is a more applied one, mostly aiming at regulating or defining 15 different infrastructure standards or at disseminating information on preparedness. In terms of the legislative documents, a regional focus was put on Germany and the EU since policies could not be assessed for each country on a global scale and this research was conducted as part of the research project "KIRMin -Critical Infrastructures Resilience as a minimum Supply Concept" focusing on a German case study. The policy and practice documents covered publications by international, European and German organizations working in the field of disaster risk reduction and civil protection (e.g. the United Nations 20 Office for Disaster Risk Reduction) as well as research councils, consultancies and other bodies.
All documents in both streams were then analyzed through an in-depth content analysis. to code for: For that purpose, a coding system was developed and manually applied to the documents (roughly 5,500 pages in total), using MaxQDA software. The analysis was therein guided by the following questions: How are critical infrastructures (CI), minimum supply and social vulnerability to CI failures dealt with in terms of: detected Detected gaps within and between CI, minimum supply and social vulnerability.

3.
Literature Review: Current treatment iesof critical infrastructure 30 A number of clear patterns and trends can be discerned from the analysis. First, the overall number of scientific publications dealing with critical infrastructure in the context of disaster risk has been rapidly rising since the early 2000s (Figure 2), indicating the growing significance of the topic. The increase can be ascribed to a mounting recognition of critical infrastructure protection on national levels since the mid-1990s. During this time, for instance the US President's Commission on Critical Infrastructure Protection (PCCIP) was created (Dahlberg et al. 2015). Over the next years several other countries followed with own programmes on infrastructure protection (Lindovsky 2014). The review suggests that a major focus CI protection was on terrorist attacks, natural hazards and industrial disasters (see also Rey 2013). 5 However, in thematic terms also a number of key differences can be identified. In absolute numbers papers dealing with disaster resilience and social vulnerability have increased most over time although In absolute numbers pdealing with disaster resilience and social vulnerability have increased most over timeHowever, the majority of papers deals with CI as one out of many sources of vulnerability in disaster contexts and does not focus on CI and vulnerability at its corea large number is not exclusively related to CI but rather names infrastructures as one source of vulnerability in the context of disasters. In parallel 10 also a notable increase of publications on CI and preparedness as well as on CI and disaster resilience can be observed. At the same time only very few papers are available which focus on minimum supply or minimum requirements for critical infrastructure and the related social vulnerability. gives an overview on policy and scientific literature on the different topics The vast majority of scientific papers analyzed are written from a rather technological point of view. They hence concentrate heavily on technological challenges with CI systems and their management. If challenges beyond such technological 15 perspectives are considered, they mostly revolve around the management of CI, especially in terms of transboundary management as well as public-private constellations (cf. NATO 2007, Smedts 2010. End userswhether businesses or householdstend, if mentioned at all, to be treated as rather passive recipients who face difficulties in case of CI failures.
Businesses are mostly mentioned in the context of economic damages in case of CI disruption, while individuals or households remain mostly generalized without referring to specific societal groups with distinct demands. 20 The case studies given in the body of literature can be divided into two main groups. While cyber-attacks and ICT failures are mentioned in a number of papers there are hardly any concrete cases assessed extensively. Concrete case studies are rather limited to disasters induced by natural hazards, mostly flooding as well as storms and snow storms. Also a regional focus on cases from developed countries and particularly the US could be detected. Especially the impacts of hurricanes Katrina (cf. Oh et al. 2010, Grigg 2012, Grubesic & Matisziw 2013, Urlainins et al. 2014, Kelman et al 2015, Cutter 2016 Economic impacts make for the predominant emphasis in such assessments (e.g. Oh et al. 2010, Chopra & Khanna 2015, Pant et al. 2016, Critical 5 2015 as e.g. in the case of the Fukushima event in 2011 (UNISDR 2014, Pescaroli & Kelman 2017. Another emphasis is put on the need for improved preparedness in these countries (e.g. Kaneberg et al. 2016). Papers on disasters in developing countries (e.g. the earthquake in Haiti) rather focus on humanitarian impacts from CI 30 failure (e.g. Oh et al. 2013, Pescaroli & Kelman 2017. Apart from very few exceptions (policy documents: D-A-CH 2013, BMI 2016, as well as few research papers: Pye et al. 2011, Miles 2015, Pescaroli & Alexander 2016, there is a distinct lack of documents that discuss critical infrastructure resilience, minimum supply and social vulnerability in an integrated manneror even name the three elements in the same document. They all share a non-technocratic perspective that addresses societal demands. The following sections will provide a more detailed analysis on current debates regarding these three topics across all types of documents analyzed (Figure 3)..

Actors and definitionsDefinitions of critical infrastructure originate almost exclusively from policy and legal documents.
Definitions and sectors of critical infrastructures vary between different countries, although most would comprise energy, water, food, transport, telecommunications, health, as well as banking and finance (Ridley 2011). In the German context CI is 5 defined as "organisational and physical structures and facilities of such vital importance to a nation's society and economy that their failure or degradation would result in sustained supply shortages, significant disruption of public safety and security, or other dramatic consequences" (BMI 2009). A review of the academic papers suggests that defining CI is not a research topic in itself, as definitions in research documents are either taken from policy, e.g. national definitions, or are adapted from these sources. 10 In the German case responsibilities for protecting CI are mainly with the Federal Ministry of the Interior and its subsidiary organizations, particularly the Federal Office for Civil Protection and Disaster Response and the Federal Office for Information Security BSI (BSI 2015b). The primary responsibilities for civil protection however are on the Federal State levels (BMI 2005).
Each federal state has its own disaster management law while there are national laws for different aspects of CI such as water (BMJV 1970) or food supply (BMJV 2017) and IT (BSI 2015, Dietzsch et al. 2016. In case of a 15 CI failure, triggered e.g. triggered. by natural hazard events s likesuch as floods, responsibilities will be located with governmental authorities at the affected level, depending on the scale of the event either at district, federal state or national one (BBK 2015a).
The responsibilities for CI management in disaster situations are particularly addressed mainly in policy documents. Across most contexts and sectors, duties and responsibilities are shared between governmental authorities and private infrastructure 20 providers, the latter of whom usually take care of the supply under normal conditions. This is also the case in Germany where estimates suggest that around 80% of the critical infrastructures are managed by private operators or are state-owned enterprises (BBK 2010b), e.g. there are overall around 370,000 operators in the food production sector (BSI 2015a). While these suppliers are responsible for the continuous supply, governmental authorities take responsibility for delivery by providing the framework conditions to protect CI (BMI 2005, BBK 2012, UP-KRITIS 2014a, 2014b There is no universal definition ofIn the caseterms of minimum supply with critical infrastructure servicess there is no universal definition,, neither in research nor policy or legislatlegislative documentsion. If at all, minimum supply levels are rather given for differenselectedt infrastructures, such as drinking water. In principle, Mminimum supply with questions are addressed CI is tackled predominantly in policy (e.g. BMJV 1970, EC 2016b or even humanitarian relief publications (e.g. IFRC 2011, IRP 2010, UNISDR 2014) and to a much lesser extent in scientific publications and to a much lesser extent in the 30 scientific community.
Interestingly, the discussion of responsibilities for securing minimum supply levels in times of major CI failure is almost entirely limited to policy documents. Actors seen as being Rresponsible actors for securing minimum supply levels are basicallymainly the samethose who are also in charge of as for the the regular supply with the respective critical infrastructures.
Policy documents from different national contexts suggest that Iin declared emergency situations the command is usually transferred to governmental crisis units with governmental actors, who are then would also be in many cases allowed permitted to intervene in private suppliers' decisions. In addition, actors from in the field of emergency response, e.g. like civil defensedefence authorities, fire brigades or actors from healthcare, are typically seen as having a shared responsibility involved in supplying to supply populations in need. Furthermore, most policy contexts hold the population itself is held at least partly 5 responsible for their own basic supply, as e.g. recommended in the in the case of the German civil defensedefence strategy (BMI 2016). But a discussion of the role of actors and their responsibilities is almost entirely limited to policy documents.
Social vulnerability is hardly mentioned in policy documents dealing with CI failure. Further, it is typically not defined clearly. and far from being defined, usually Most documents consider supply for "the population" as a whole in crisis situations, is dealt with instead of distinguishing between different societal groups with differentiated social vulnerabilities. If 10 mentionedused, the notion of vulnerability mostly is mostly applied to refers either to the healthcare contexts or it is dealt with in studies analysing the analysis of previous outages and their impacts.

Current state and focal areas of critical infrastructure research and policyThematic foci and context application 15
While critical infrastructure in general is not a new topic, much ofmost of the research on the topic research was and is focussed on technical aspects of infrastructure system and questions of how to maintain and restore functionalitiesfunctionality despite hazards. Overall CI protection is focusing almost exclusively on assigning responsibilities and defining technical standards, resilience is almost exclusively seen in a rather technological perspective with a focus on continuous provision or timely recovery of CI services even in times of hazards, crises and disasters , D-A-C-H 2013, Ortenzy 2013, Münzberg et al. 2015. Also the academic literature has a strong focus on achieving CI resilience from a technological perspective , Cimellaro 2014).The responsibilities for CI management in disaster situations are particularly addressed in policy documents. Across most contexts and sectors, duties and 30 responsibilities are shared between governmental authorities and private infrastructure providers, the latter of whom usually take care of the supply under normal conditions. This is also the case in Germany, where despite existing policies such a shared responsibility has the potential to result in murky responsibilities with unclear risk burdens and liability in crises situations (Van Aaken & Wildhaber 2015) : Estimates suggest that around 80% of Germany's critical infrastructures are managed by private operators or are state-owned enterprises (BBK 2010b), e.g. there are overall around 370,000 operators in the food production sector (BSI 2015a). While these suppliers are responsible for the continuous supply, governmental authorities take responsibility for delivery by providing the framework conditions to protect CI (BMI 2005, BBK 2012, UP-KRITIS 2014a, 2014b. In the German case responsibilities for protecting CI are mainly with the Federal Ministry of the Interior and its subsidiary organizations, particularly the Federal Office for Civil Protection and Disaster Response and the Federal Office for 5 Information Security BSI (BSI 2015b). The primary responsibilities for civil protection however are on the Federal State levels (BMI 2005). Each federal state has its own disaster management law while there are national laws for different aspects of CI such as water (BMJV 1970) or food supply (BMJV 2017) and IT (BSI 2015, Dietzsch et al. 2016.
In case of a CI failure triggered e.g. by natural hazards like floods responsibilities will be located with governmental authorities at the affected level, depending on the scale of the event either at district, federal state or national one (BBK 2015a). Overall 10 CI protection is focusing almost exclusively on assigning responsibilities and defining technical standards, not only in Germany but also in other European countries like Austria (Bundeskanzleramt Österreich 2015) or Switzerland (Lauta 2015,

VBS & BABS 2016).
Besides CI assets another focus in policy is on aspects of civil protection in case of an outage. In the German context a huge 15 number of documents from governmental authorities is available to inform citizens about private precautionary measures, including the stockpiling of minimum supplies as preparatory measure for potential blackouts. The 2016 civil defensedefence strategy recommends German citizens to get equipped with food for ten days and two literlitre of potable water for a period of five days as well as to keep warm clothing and blankets in stock to cope with power outages (BMI 2016). On the supply side the German water security law (Wassersicherstellungsgesetz) calculates a vital supply of 15 literlitre of drinking 20 water/day/capita for each citizen, but 75 literlitre/day/bedside for hospitals and healthcare facilities and 150 literlitre/day/bedside for surgery and infection facilities or respective departments for at least 14 days in case of crisis (BMJV 1970).
Further, both documents (BMI 2016, BBK 2016c) recommend private stocking of necessary medical equipment and to prepare for short-term power outages. However, except for medicine there is no differentiation between societal groups. Other 25 publications also recommend backup generators or other devices to compensatecope with (longer) power outages (BBK 2010a, BBK 2015b). For some critical infrastructures there are no regulations to maintain minimum functions, e.g. for sewage where no backup generators are demanded in case of a power outage (BBK 2010a).
All of this can be considered as related to minimum supply, although the term itself is not mentioned. Besides (national) policy it is the international humanitarian literature that gives some guidance on minimum standards, although mostly limited to 30 water, food and health care. Among others the SPHERE handbook (IFRC 2011) provides guidance on minimum supply with water, food, and othersother things in case of disaster,. However however, it does not mention critical infrastructures as such, indicating a potential missing link between the views of infrastructure and humanitarian communities on minimum CI supply standards. Scientific literature in this field seems still scarce.
Both, scientific and policy literature address vulnerabilities in relation to CI failures. Most of the policy documents e.g. in the German context, stress the vulnerability of the population at large to CI failures and stress private prevention measures (e.g. BBK 2015a, BBK 2016b, BBK 2015b). The review suggests that the only context in which differential vulnerability within the society is discussed explicitly is the health sector. In a crisis situation with limited availability of medical services, the classification and prioritization of groups of patients, based on survival rates and available resources, seems to be widely 5 accepted across different contexts (Rosenbrock & Gerlinger 2004, BSI 2016. Differences between rural and urban communities are mentioned in case of emergency water supply, where scarcely populated rural areas pose bigger challenges for authorities to provide the statutorily determined minimum supply (BBK 2013, BBK 2016a).
Research literature highlights three groups and their vulnerability to long-term critical infrastructures disruptions: the elderly , people in need of healthcare and low-income households. In addition the place of residence matters, i.e. 10 in a case study in Virginia, USA,  found urban settlers more vulnerable to impacts from flood and storm surge but rural dwellers more vulnerable to CI disruptions that occurred due to the disaster events (cf. . Vulnerable groups also often live in places with above-average vulnerability at large (cf., . Other studies linked poverty to a lack of disaster less preparedness to disasters, e.g. if healthcare is anyway weak (cf. study of Banks et al. (2016) in central Appalachia, USA), or if food security is not given (e.g. Cutter (2016)  instead of focusing only on quantitative structural stability,. This is which is in line with Comes (2016) who claims that although communities are recognized as being at the heart of resilience, research still focuses on more on responders instead of considering individuals or local communities as actors. Empirical studies on CI resilience are still rare and "still focus on activities within the boundaries of the CI" (Labaka et al. 2014: 431) and much less on the "well-being of all citizens through the availability of essential goods and services" (Ridley 2011: 111), underlining the demand for more studies on community 30 or societal group level.
Another gap detected in scientific and policy literature is related to the question how the demands for minimum supply demands differ among between societal groups. Policy sourcesdocuments were found to distinguish only between demands for healthcare (e.g. different supply levels for hospitals) but rather view 'the population' in a uniform way. EvenAlso scientific papers provided only few statements on minimum or failed supply of local communities or distinctly vulnerable societal groups or even whole regions and countries. In a study on healthcare infrastructure in Ghana, Kenya, Rwanda, Tanzania and Uganda Hsia et al. (2012) found that less than 65% of all hospitals have basic infrastructure components such as reliable sources of water and electricity. This is far the below the global level of coverage recommended by the World Health Organization (WHO). Miles et al. (2011) report that in case of a blackout in San Diego, USA, patients are transported to those healthcare 5 facilities that have backup generators. Münzberg et al. (2015) discuss the importance of knowing the critical point in time at which all backup capacity is depleted.
Only few research papers address the relationship between CI, (social) vulnerability and supply problems in past CI failures.
However there was not a single paper for which this relationship provided the major or explicit emphasis. Rather, the few documents addressing the relationship did so on a side note, e.g. mentioning risks for dialysis patients in need of healthcare Some papers suggest that In the end it is the individuals' preparedness to CI failures that is heavily contributing is eventually decisive for to societal resilience at large . CI (minimum) supply in case of a disaster in the end is a question of ethical choices --who does receive how much and based on which reasons? Addressing these questions requires and understanding of CI systems that goes beyond the purely technical dimensions . However aspects of fairness of CI supply and related ethical debates are rather tackled in humanitarian literature (IFRC 2011, Moodley 30 et al. 2013)) but much less in CI policy (EC 2016b) and research where it seems to be a blind spot. In the German context for instance growing demands of more people hospitalized or in need of home care would call for studies on the question in how far their emergency supply could be sustained (BBK 2012b).
As summarized in Figure 4, there are few gaps in defining CI and CI management and the related actors as well as their responsibilities. Particularly social vulnerabilities to CI failures are hardly dealt with in CI research and policy. Thus, a significant gap in research on the vulnerabilities of different social groups to CI outages as well as related policies was detected.
In addition, potential mutual intensification or reduction of minimum supply and social vulnerabilities are greatly neglected. 5

Critical infrastructure and critical infrastructure resilience
Definitions of critical infrastructure originate almost exclusively from policy and legal documents. Definitions and sectors of critical infrastructures vary between different countries, although most would comprise energy, water, food, transport, telecommunications, health, as well as banking and finance (Ridley 2011). In the German context CI is defined as "organisational and physical structures and facilities of such vital importance to a nation's society and economy that their 10 failure or degradation would result in sustained supply shortages, significant disruption of public safety and security, or other dramatic consequences" (BMI 2009). A review of the academic papers suggests that defining CI is not a research topic in itself, as definitions in research documents are either taken from policy, e.g. national definitions, or are adapted from these sources.
The responsibilities for CI management in disaster situations are particularly addressed in policy documents. Across most 15 contexts and sectors, duties and responsibilities are shared between governmental authorities and private infrastructure providers, the latter of whom usually take care of the supply under normal conditions. This is also the case in Germany, where despite existing policies such a shared responsibility has the potential to result in murky responsibilities with unclear risk Policy challenges, e.g. coordination among EU countries, are addressed both in policy documents (CEPS 2010, EC 2016a, Commission of the European Communities 2006, EC 2008 and research papers , Rehak et al. 2016). In addition, several research papers also raise doubts about lacking policies and unclear responsibilities (Van Aaken and Wildhaber 2015, Kitagawa et al. 2016), Policy literature has a strong and growing focus on resilience-based approaches for CI protection (CEPS 2010, D-A- , 5 Brasset and Vaughan-Williams 2015, McGee et al. 2015. A growing number of countries has either adopted a resilience framing to CI over the past years, e.g. Australia (JRS-IPSC 2012), Canada and New Zealand (New Zealand Government 2011, Critical five 2014) or shows tendencies to focus more on resilience issues, such as the US (Dahlberg et al. 2015), the EU and various European countries (Brasset and Vaughan-Williams 2015, UP KRITIS 2014b). Here CI resilience is almost exclusively seen in a rather technological perspective with a focus on continuous provision or timely recovery of CI services 10 even in times of hazards, crises and disasters , D-A-C-H 2013, Ortenzy 2013, Münzberg et al. 2015.
Also the academic literature has a strong focus on technological perspective towards CI resilience , Cimellaro 2014 although some papers raise questions on shortcomings of a limited technological perspective. Sage et al. (2015) call for a more socio-ecological understanding of infrastructure which is in line with Comes (2016) who claims that although communities are recognized as being at the heart of resilience, research still focuses on more 15 on responders instead of considering individuals or local communities as actors. Empirical studies on CI resilience are still rare and "still focus on activities within the boundaries of the CI" (Labaka et al. 2014: 431) and much less on the "well-being of all citizens through the availability of essential goods and services" (Ridley 2011: 111), underlining the demand for more studies on community or societal group level.

Minimum supply 20
There is no universal definition of minimum supply with critical infrastructures, neither in research nor policy or legislation.
If at all minimum supply levels are rather given for different infrastructures. Minimum supply with CI is tackled predominantly in policy (e.g. BMJV 1970, EC 2016b or even humanitarian relief publications (e.g. IFRC 2011, IRP 2010, UNISDR 2014 and to a much lesser extent in the scientific community. In the German context a huge number of documents from governmental authorities is available to inform citizens about private 25 precautionary measures, including the stockpiling of minimum supplies as preparatory measure for potential blackouts. The 2016 civil defense strategy recommends German citizens to get equipped with food for ten days and two liter of potable water for a period of five days as well as to keep warm clothing and blankets in stock to cope with power outages (BMI 2016). On the supply side the German water security law (Wassersicherstellungsgesetz) calculates a vital supply of 15 liter of drinking water/day/capita for each citizen, but 75 liter/day/bedside for hospitals and healthcare facilities and 150 liter/day/bedside for 30 surgery and infection facilities or respective departments for at least 14 days in case of crisis (BMJV 1970).
Further, both documents (BMI 2016, BBK 2016c) recommend private equipment of necessary medical equipment and to prepare for short-term power outages However, except for medicine there is no differentiation between societal groups. Other publications also recommend backup generators or other devices to compensate (longer) power outages (BBK 2010a, BBK 2015b). For some critical infrastructures there are no regulations to maintain minimum functions, e.g. for sewage where no backup generators are demanded in case of a power outage (BBK 2010a). 5 Besides policy it is the humanitarian literature that gives some guidance on minimum standards, although mostly limited to water, food and health. Among others the SPHERE handbook (IFRC 2011) provides guidance on minimum supply with water, food, and others in case of disaster, however it does not mention critical infrastructures as such, indicating a potential missing link between the views of infrastructure and humanitarian communities on minimum standards. Scientific literature in this field seems still scarce. 10 Responsible actors for minimum supply are basically the same as for the regular supply with critical infrastructures. In declared emergency situations the command is transferred to crisis units with governmental actors, who then would also be allowed to intervene in private suppliers' decisions. In addition actors from emergency response like civil defense authorities, fire brigades or actors from healthcare are involved in supplying population in need. Furthermore the population itself is held at least partly responsible for their own basic supply, as e.g. recommended in the civil defense strategy (BMI 2016). But a discussion of the 15 role of actors and their responsibilities is almost entirely limited to policy documents.
A gap detected in both bodies of documents related to the question how minimum supply demands differ among societal groups. Policy sources were found to distinguish only between demands for healthcare (e.g. different supply levels for hospitals) but rather view 'the population' in a uniform way. Even scientific papers provided only few statements on minimum or failed supply of local communities or distinct vulnerable societal groups. In a study on healthcare infrastructure in Ghana, 20 Kenya, Rwanda, Tanzania and Uganda Hsia et al. (2012) found that less than 65% of all hospitals have basic infrastructure components such as reliable sources of water and electricity. This is far the below the level of coverage recommended by the World Health Organization (WHO). Miles et al. (2011) report that in case of a blackout in San Diego, USA, patients are transported to those healthcare facilities that have backup generators. Münzberg et al. (2015) discuss the importance of knowing the critical point in time at which all backup capacity is depleted. 25

Social vulnerability
Both bodies of documents address vulnerabilities in relation to CI failure. However, the vast majority focusses on vulnerabilities of the critical infrastructures themselves and ways to reduce that vulnerability, without defining it further. Social vulnerabilities are mentionedif at allonly briefly and vaguely. A significant gap was therefore detected, which applies to both fields (research and application). 30 Most of the policy documents e.g. in the German context, stress the vulnerability to CI failures of the population at large and stress private prevention measures (e.g. BBK 2015a, BBK 2016b, BBK 2015b). The review suggests that the only context in which differential vulnerability within the society is discussed explicitly is the health sector. In a crisis situation with limited availability of medical services, the classification and prioritization of groups of patients, based on survival rates and available resources, seems to be widely accepted across different contexts (Rosenbrock & Gerlinger 2004, BSI 2016. Differences between rural and urban communities are mentioned in case of emergency water supply, where scarcely populated rural areas pose bigger challenges for authorities to provide the statutorily determined minimum supply (BBK 2013, 5 BBK 2016a. A few research papers address the relationship between CI, (social) vulnerability and supply problems in past CI failures.
However there was not a single paper for which this relationship provided the major or explicit emphasis. Rather, the few documents addressing the relationship did so on a side note, e.g. mentioning risks for dialysis patients in need of healthcare in a case study in Virginia, USA,  found urban settlers more vulnerable to impacts from flood and storm surge but rural dwellers more vulnerable considering related CI access (cf. . Vulnerable groups also often live in places with above-average vulnerability at large (cf., . Other studies linked poverty to less preparedness to disasters, e.g. if healthcare is anyway weak (cf. study of Banks et al. (2016)  In the end it is the individuals' preparedness to CI failures that is heavily contributing to societal resilience ).
CI (minimum) supply in case of a disaster in the end is a question of ethical choices --who does receive how much and based on which reasons? Addressing these questions requires and understanding of CI systems that goes beyond the purely technical dimensions . However aspects of fairness of CI supply and related ethical debates are rather tackled in humanitarian literature (IFRC 2011, Moodley et al. 2013) but much less in CI policy (EC 2016b) and research where it seems to be a blind spot. In the German context for instance growing demands of more people hospitalized or in need of home care would call for studies on the question in how far their emergency supply could be sustained (BBK 2012b). 5 As summarized in Figure 4, there are few gaps in defining CI and CI management and the related actors as well as their responsibilities. Particularly social vulnerabilities to CI failures are hardly dealt with in CI research and policy. Thus, a significant gap in research on the vulnerabilities of different social groups to CI outages as well as related policies was detected.
In addition, potential mutual intensification or reduction of minimum supply and social vulnerabilities are greatly neglected.

4.
Framing the relationships between critical infrastructure, social vulnerability and minimum supply 10 Building on the results of the review, Figure 5 provides a heuristic model for framework for capturing the relationship between critical infrastructure failure, minimum supply and social vulnerability. We argue that the impacts from critical infrastructure failure are modulatedi.e. amplified and/or mediatedby social vulnerability as well minimum supply. The latter two are in turn coupled in a functional and normative relationship. In line with the use in risk and disaster research, vulnerability is understood here as the predisposition of social actors to suffer harm when exposed to a hazard (Wisner et al. 2004). The 15 immediate hazard can in this context be the failure of critical infrastructure supply such as water or electricity which, in turn, can be triggered by other hazards, for instance floods, tsunamis, storms or other non-environmental hazards such as terrorist attacks. The analysis of social vulnerability towards critical infrastructure failure has the potential to inform the planning and design of minimum supply schemesand it should do so in our eyes. In return, a secured minimum supply can defuse social vulnerability and therefore buffer otherwise higher impacts. Given the modulating effects of minimum supply and social 20 vulnerability, the resulting impacts from critical infrastructure failure can therefore be higher or lower. In any case, the impacts can be expected to be differentiated socially, spatially and functionally.

Discussion: A future agenda for science and practice
In combination of the gaps identified in the review (section 32) and the conceptual framing (section 34) we argue that a number of needs can be identified that can drive future science, practice and policy agendas: 25 In terms of scientific knowledge,The literature review revealed that considerable knowledge gaps remain with regards to the ways in which different parts of the society are vulnerable differently to the failure of critical infrastructure and the resulting lack of supply with goods and services, most importantly water and electricity. While vulnerability assessment in in the context of environmental hazards has made great methodological advancements over the last years (Birkmann 2014), this literature has almost exclusively referred to the direct and immediate influences of environmental hazards, e.g. how vulnerable 30 households if affected immediately by flooding. In addition to this focus vulnerability assessment concepts and methods also need to be appliedand adjustedto assess the secondary effects of natural hazard impacts emerging from CI failure. This is not an easy task, given that in many contexts social actors cannot draw on experiences with respective reference scenarios.
Estimating one's own vulnerability, i.e. predisposition for suffering harm, in case of, for example, an extended blackout or water shortage might therefore prove difficult. CI disruptions in the course of natural hazard-induced disasters and the (private) 5 preparedness to outages has not been at the core of vulnerability research so far although it notably is an important and lifesaving issue. Not having any experiences with previous outages can exacerbate the vulnerability due to lack of preparedness, as e.g. one could see in Germany where private preparedness and stock-piling advices in the 2016 civil defense strategy were not taken serious, among others because of, inter alia, the very high reliability ofof CI.
An additional challenge deserving attention is the potentially fine-gridded differentiation across social groups, space and time 10 (following up on authors like Handmer (2003) and Barnet et al. (2008) who stressed the need for scale and context specific approaches for vulnerability reduction). . While such differentiation is a common property of vulnerability in many contexts, it is particularly challenging for the context of minimum supply. This is because the infrastructure behind most services, e.g. electricity and water, is designed for larger system entities. For instance, the social vulnerability towards suffering impacts from a sustained blackout might differ within a single multi-apartment block, e.g. comparing an elderly and immobile person 15 with a cardiovascular disease and dependence on electrical medical equipment to a group of young students sharing the apartment next door. Yet at the same time, the electricity grid cannot deliberate supply on such a high resolution as it functions in much larger entities, e.g. switching on or off entire neighborhoods of a city. Question of timing complicate the situation even further, as secondary concerns such as power for food production facilities can become primary concerns over time, in case of a prolonged CI failure. As a consequence rethinking if CI supply can be more group-specific and how far that would 20 be feasible at all is something worth being discussed.
Apart from these rather technical scientific problems, a set of very important questions emerges at the science-policy interface.
These questions address with respects to normative and procedural issues of distributional justice and responsibility. The review of practical management contingencies and legal as well as policy documents (section 23) suggests that practice and policy has been cautious in defining minimum supply levels for few critical infrastructure sectorshowever they hardly differ 25 for different social groups, regions, secondary infrastructure etc. While it seems to be easier to provide numbers for certain sectors, e.g. for water supply (see above), for other sectors supply levels stay rather vague or are limited to rather general statements that the infrastructure provision should be restored as soon as possible after a disruption. Along the same line, practice and policy has also struggled to define the ways in which minimum supply is to be prioritized in situations of limited capabilities and resources, i.e. in crises and disaster situations. Lastly, the question of who isand shouldbe responsible for 30 the provision of minimum supply remains strikingly open in many respects and contexts. Most likely a higher resilience would demand efforts at both ends, the supplier and the end user side. However, how the burden isand should beshared is of surprisingly little societal, political and academic debate.
Yet, wWhile science can and should play a key role in tackling these questions, we argue that none of these questions can and should be resolved in a technocratic manner. Scientific knowledge on, for instance, socio-spatial patterns of vulnerability does not automatically lead to "objective" prescriptions or even recommendations on necessary action, prioritization and responsibility. These aspects are rather need to be tackled and resolved in a wider societal debate that addresses the social contract for risk reduction and shifts the decision-making into the political realm of wider risk governance. In that sense, the 5 agenda ahead is one of transdisciplinary co-production and societal debate, rather than of risk science and critical infrastructure management alone.

Conclusion
The analysis presented in this paper has shown that scientists, risk practitioners and policy makers are increasingly concerned about the links between critical infrastructure and disasters. Scientific literature, policy documents, legal frameworks and 10 guidance documents for risk reduction practices therefore engage evermore with the topic of critical infrastructure resilience and its management in crises and disaster situations. However, the links drawn to minimum supply contingencies or the assessment of socially differentiated vulnerability towards CI failure remain to be strikingly weak, if not absent in many contexts. The existing gap between these perspectives is a grave shortcoming as it inhibits a comprehensive understanding of the risks related to critical infrastructure failure and successful disaster risk reduction policies and practices. The paper 15 therefore put forward a framework heuristic model that helps to decipher the linkages between critical infrastructure resilience, minimum supply and social vulnerability in an inclusive manner, thereby providing guidance for future research agendas and policy as well as practice. However, the analysis also strongly shows that the main challenges might not lie within the technological or managerial questions to be solved, but in the normative, ethical and political questions around the responsibility for and prioritization of minimum supply at the fuzzy interface of state organs, private-sector CI utilities, civil 20 society and affected individuals themselves, the latter of which are more often than not are amongst the weakest, most vulnerable and resource-poor parts of society. Moving the discourse on the responsibility for minimum supply and preventive risk reduction to a stage of more explicit political and societal debate is therefore urgently needed, particularly in view of the increasing levels of disaster risk to be expected in the future.   General comments This is an interesting topic that explores a challenging topic. With some re-structuring and a more distinct argument made for exploring the role of 'minimum supply' concepts in DRR, the paper would be much stronger. As it stands, I found it a little difficult to follow the argument's narrative, so I remain to be convinced that 5 there is an issue worthy of further detailed explanationthat is, is there a role for minimum supply (conceptually or technically) beyond that which appears to already be set out in many of the policy documents examined. It is unclear to me whether the argument has been made that it is reasonable or even technically feasible to expect minimum supply to the broad array of stakeholders/community members mentioned in the paper? In my view, the paper would be stronger were it to make that case, and then testing that idea against current literature and practice 10 to explore issues of feasibility, justice, etc. Moreover, I found the scope of the literature and policy review a little hazy. Is the literature review globaland in which disciplinary fieldsand the same re the policy review. And is the German case then situated within these, or was the literature review global and the policies examined only EU? Figure 1 only helps a little to clarify this, and it would be better to be clearly explained in the method. The paper 15 does not yet do what its title suggests. Perhaps the title might be something more like, "is there a role for min supply concept in better linking CI and social vulnerability'? Finally, the paper sets out to provide a framework, but I could not find it.
We thank the referee for his very detailed review. Most of the issues raised in the text above will be dealt with in 20 detail in the below section where we respond to the detailed comments.
In general, we believebased on our review and analysis of the status quo --that minimum supply so far has not been discussed sufficiently in CI debates that mostly focus on technical feasibility and speedy restoration after any kind of disruptions. Therefore our focus would remain on this part, however the question if it is reasonable or even technically feasible to expect, receive or privately stockpile minimum supply of different CI will be addressed more 25 comprehensively in the paper revision.
The literature review itself was done based on search terms given in the paper, all disciplinary fields were included in the basic search, and we will add that in the paper. While the scientific review had no regional focus the policy part arguably focused on the German/European contexts, the decision will be emphasized in the methodology section. 30 The critical comment on the conceptual framing is well-taken. The framework in the latter part of the paper is meant to provide heuristic guidance and to stimulate the discussion. It is not meant to provide a fully-fledged framework.
In revising the paper, we will make sure to change the wording accordingly and shifting the emphasis away from the conceptual framing.

35
Responses to detailed comments (comments are written in italics, newly written parts are highlighted in blue): 1. Comment: Specific comments Pg1 Line 11unclear why they should be Line 13 -are the "remaining gaps in management" to be informed by an understanding of social vulnerability Reply: You refer to the sentence "Increased attention has lately been given to, first, social vulnerability reduction and, second, critical infrastructure management in the context of natural hazards and disasters. However, strikingly little efforts have been made in linking the two in a coherent manner conceptually and practically. Addressing this gap is the objective of this paper. In its first part, it provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding 5 of social vulnerability towards failures during and after disasters." Given the limited space in an abstract we would slightly modify this paragraph as follows: "Increased attention has lately been given to, first, social vulnerability reduction and, second, critical 10 infrastructure management in the context of natural hazards and disasters. However, strikingly little efforts have been made in linking the two in a coherent manner conceptually and practically. Addressing this gap to point to a new path towards a more integrative perspective towards critical infrastructure resilience is the objective of this paper. In its first part, it provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding of social vulnerability towards failures 15 during and after disasters."

Pg 2 Footnote on line 7why not draw on this to establish the argument for the connection?
Thanks to the referee for the valuable comment. We will highlight this conferenceas well as other recent 20 activities such as the important role of CI in the SFDRR and the DRR4NAP meeting where CI played an important rolemore in chapter 3 to strengthen the need for integration

Line 13 -impacts 'may' have not necessarily 'will' 25
Will be corrected in paper revision

Line 22what's the difference between normative and political questions, and where are these explored in the paper?
Normative are not necessarily equal to political questions. While there certainly is an overlap when it comes 30 to setting norms for e.g. minimum standards however not all normative questions are tackled in political debatesthis is discussed particularly in the chapter on social vulnerability and its poor consideration in CI and minimum supply debates.

Line 24how does/should CI failure feature in DRR plans/
This has not been the focal research area but will be emphasized by adding on the role of CI in international DRR documents and frameworks

Line 24 -define 'disastrous effects' This paragraph raises the questionwhat is technically feasible? Is 40 min supply to all houses all the time reasonable? Would it provide a perverse incentive for a lack of preparedness?
We agree this is a crucial point in this debate which has not been discussed sufficiently in the paper. We will strengthen that topic in the discussion section. 45

Pg 3 Line 1 -'caused ridicules'?? Was ridiculed? By whom? Such claims require evidence/references
Reference to the respective newspaper articles will be added, such as BBC 2016; Financial Times 2016; Spiegel 2016 50 8. Line 3 -why is the nexus problematic? Isn't the paper arguing for their connection?
Yes we are arguing that critical infrastructure failure, social vulnerability and minimum supply are linked in reality but that they so far are hardly dealt with in a nexus or integrated approachwhat is problematic 9. Line 5practical/politicalthese are two very different things. 5 Agreed, sentence will be changed: It has two main objectives: First it aims at exploring the current stateof-art regarding the scientific understanding and practical as well as political approaches on this nexus.

Line 6 -what is meant by 'most relevant communities of practice'? (disciplines or industry? Just because CoPs have a particular definition in my world) 10
Thanks for the remark, "in the most relevant communities of practice." could be deleted.in this case we meant actors dealing with CI in policy and practice 11. Pg 3 Method Line 16is a structured review the same as a systematic review? And is the description of Scopus necessary? Figure 1 didn't really help mesorry. What about papers that addressed 2/3 of the 15 topics? Structured would mean the same as systematic -we will change to "systematic review" what probably is more clear. Normally the database used for systematic surveys is mentioned, therefore we would prefer to keep that. Papers addressing 2/3 of the topic would be highly relevant, will be made clearer by changing page3, line 21/22 to (i.e. contributions that explicitly talk the linkages between CI failure, social vulnerability 20 and minimum supply or at least two of them). Figure 1 was intended to illustrate the search but could be deleted.

Line 30 -what 'other sources'?
"from other sources" will be deleted, in fact it was snowball sampling starting from authorities working on 25 DRR and CI 13. Line 31 -"with over 4,500 pages (irrelevant): : :.. to literature" could be deleted Agreed 30 14. Pg 4 Line 1-this is where the scope and context of the review becomes quite unclear. "in terms of legislative documents, a regional focus": : :. It would be useful to have this all set out earlier; that this focus is situated within the broader review Agreed, we will include that earlier in the introductory part and the abstract 35 15. Lines 7 -9 could be deleted and replaced with "All documents were analysed through content analysis using MaxQDA software to code for:" Thanks, will be done in revised text

Line 10what about different combinations of interactions? Between all three, between two. Eg is the 40
concept of minimum supply explored mostly in document relating to CI.
In that paragraph we refer to our coding scheme which was guided by the questions listed here. However, looking for such interactions was part of the later analysis. Here referee #2 suggested to include a table with the literature we found for the different topics and in that table we indicate the papers that dealt with such interactions. 45

Line 18-19rapidly rising and growing significance mean virtually the same thing
Agreed, however we refer to rising numbers of papers and the growing significance of the topic, thus we would rather keep the sentence as it is "First, the overall number of scientific publications dealing with 50 critical infrastructure in the context of disaster risk has been rapidly rising since the early 2000s ( Figure  2), indicating the growing significance of the topic."

Line 28is unclear
We will rephrase from "[…] a large number is not exclusively related to 5 CI but rather names infrastructures as one source of vulnerability in the context of disasters." to "In absolute numbers papers dealing with disaster resilience and social vulnerability have increased most over time. However, the majority of papers deals with CI as one out of many sources of vulnerability in disaster contexts and does not focus on CI and vulnerability at its core." 10 19. Pg 5 Line 19 -'share a non-technocratic perspective that addresses societal demands" What does this mean? "non-technocratic" refers to authors like Lauta (2015) and Lievanos & Horne (2017) which we will include as referencesand that talk about the need to go beyond the traditional engineering-context that CI is often associated with and to not only talk about resilience of CI but also resilience to CI outages. We will 15 make our point more clear.
The topics are first addressed separatelyas that also matches most of the literaturethe combined summary follows then in figure 4 20

Line 30 -Should it be? Is there actually an issue here?
First this is a finding from the literature review. Second at least to us it was surprising as although there are many definitions around no research seems to be done linking them to the national/socio-cultural backgrounds. We will explicitly explain this in the paper when revising it. 25 22. Line 31 -"most" -it's unclear whether this refers to the global context or the German case, or the EU.
Global context, we will add that for more clarity 23. Pg 6 Line 14then should these be in the analysis? If the structure of the review was clearer, this might 30 make sense No, it should not as this is not the focus of our research but meant to highlight the focal areas of policy, which are then discussed in the following chapter.

Line 18 -"Lacking policies and unclear responsibilities" in relation to what and where? 35
Will be changed to "… raise doubts about lacking policies on transboundary coordination and unclear responsibilities, particularly between public and private actors"

Lines 20 + suggest an international study
The The paragraph refers to the German context, as it begins with "In the German context" it might not be necessary to add the context again here, however we will make clear that from line 17 we refer to an international context again.

Line 21 -"both bodies of documents" -German policy or the wider global context? 5
Both bodies of documents refers to scientific and policy (German and international) literature, we will rewrite to express things more clearly Healthcare is considered as CI, therefore we purposefully also included such examples. The referee is right that p08/line1 does not refer to the opening line of the paragraph, like the rest of the paragraph. We will therefore add the following: 20 "Even scientific papers provided only few statements on minimum or failed supply of local communities, distinct vulnerable societal groups or even whole regions and countries. In a study on healthcare infrastructure in Ghana, Kenya, Rwanda, Tanzania and Uganda Hsia et al. (2012)  around the argument for the link is needed.
The sentence referred to here is: "A few research papers address the relationship between CI, (social) vulnerability and supply problems in past CI failures." To make our point clearer it will be changed to "Only few research papers…" What we want to highlight is that this important linkage so far has hardly been researchedwill be emphasized to provide more clarity 40 33. Line 31 -"the place of residence matters" : : : this is about exposure and there are tomes of literature on the topic across the DRR and human geography literatureit may be worth drawing on some of these to support the point. This is without doubt true. However these papers on vulnerability and exposure did not show up in our 45 search as the vast majority of does not consider (critical) infrastructure. Therefore we would prefer not to add further references but rather to include this statement to support the point that more research is needed on this connection. We will make sure to discuss the connections to exposure more explicitly in the revision of the paper. 50 34. Pg 9 Line 1 -rural dwellers more vulnerable considering related CI access"what does this mean?
There is assumption the reader understands your point.
Here the word "related" will be deleted, sentence changed to "…  found urban settlers more vulnerable to impacts from flood and storm surge but rural dwellers more vulnerable to CI disruptions that occurred due to the disaster events" 5

Line 9 -"community preparedness in Hurricane Katrina"so?
Will be changed to "Grigg et al. (2012) claim a culture of citizen and community preparedness in the context of Hurricane Katrina, including preparedness to CI disruptions." 10 36. Line 17 -"how far their emergency supply" -do you mean Germany's? No, refers to international contexts, but so far only with reference from EU, further sources will be added. German context only from next sentence on beginning with "In the German context…" can be learned from current practice (and other fields).
Agreed that this point has to be made clearer in the beginning as it sets the context. We will emphasize it in the first chapter but would leave the figure and the chapter where it is as it also builds on the findings of the literature review. 25 39. Pg 10 Section 5 I think the order is wrong in the first sentence, no? Yes, so far refers wrongly to section 5.3, has to be section 4, will be changed 40. Line 7 -define "scientific knowledge" Refers to the scientific review/the results of the systematic literature survey, will be rephrased for more 30 clarity 41. Line 13 -"This is not an easy" : : :this is an issue for most, if not all, vulnerability assessmentsand I don't really understand the point about actors not being able to "draw on experiences with respective reference scenarios"??? However, I would encourage the authors to examine the community-based 35 DRR, communitybased adaptation, and community-based NRM literature for a counter argument. This surely is an issue for all kinds of vulnerability assessments. Nevertheless CI disruptions in the course of natural hazard-induced disasters and the (private) preparedness to outages has not been at the core of vulnerability research so far although it notably is an important and life-saving issue. Not having any experiences with previous outages (negative reference scenarios) can exacerbate the vulnerability due to 40 lack of preparedness, as e.g. one could see in Germany where private preparedness and stock-piling advices in the 2016 civil defense strategy were not taken serious, among others because of the very high reliability of CI. That point will be made clearer in the revised paper.

45
42. Line 17 -what is "fine-gridded differentiation"? Suggest the authors look at papers such as "We are all vulnerable' by J Handmer, and the 'Hazards of Indicators' by J Barnett. Thanks for the advice we will elaborate on our understanding of it, based on the mentioned and additional literature. 50 43. Line 19 -" most infrastructure is designed for larger system entities"this returns us to the need for an solid argument as to why it should be anything more than that. As stated in the sentence before different societal groups with different vulnerabilities may require different minimum standardsso rethinking if CI supply (depending on the CI) can be more group-specific and how far that would be feasible at all is something worth being discussed. This point will be emphasized and 5

strengthened.
44. Lines 20-25 -there's a need to clarify whether the authors are arguing for or against this?
The goal here was to highlight the complexity of the topic, between (necessarily) large grids providing the same level of CI (access) for everyone and social groups with potentially different demands in a small area 10 so our point would be that potentially a higher resilience would demand efforts at both ends, what will be added in this paragraph in the revised version.
45. Line 26 -"questions at the science-policy interface" -where did this come from? If it's a key discussion point then it need exploration in the findings. It's really unclear to me how this is a science-policy issue 15 when the argument (drawing on the literature or even 'expert' opinion) is not made. Thank you for this consideration. The exploration of this aspect will be strengthened in the findings section. We will also make the point more clearly why this aspect is necessary.

20
46. Pg 11 Line5 -"socio-spatial patterns of vulnerability"does this presume they are static? Not necessarily, however there are arguably some spatial patterns of vulnerability, such as rural areas where e.g. road networks may be worse or less redundant or where hospitals are further away 47. Line 7 -"these aspects need to be tackled and resolved". I wrote, Why? Where's the case for it? This  25 was the fundamental struggle I had with the paper. It may be there, but it's tucked away.
Here we argue for the need of having a wider societal debate on CI and minimum supplies, beyond the current discourses on CI which rather technological. However in case of a longer outage "only" focusing on restoring the infrastructure itself without having plans for bridging the outage phase (for different social groups) can have disastrous consequences. This point probably has to be strengthened. 30

Finally, where's the conceptual framework?
The conceptual framework is provided in section 4 of the paper, around figure 5. This is not meant to be a fully-fledged conceptual framing, let alone an theoretical explanatory framework. Figure 5 and its 35 discussion serve as a heuristic framing for ordering the key elements discussed in the literature review and stimulating further discussion. We will revise the wording and narrative of the paper accordingly.

Legal and policy documents
Research paper

Critical
Infrastructure & CI resilience