On March 16th 2022, Prof. Dr.-Ing. Klaus-Peter Holz died unexpectedly after a short illness. We, the colleagues from Hydro-Engineering and Computer Science in Civil Engineering, mourn with his family at the farewell of a good friend and long-time colleague with whom we were very familiar and worked closely together.

Peter Holz, as we called him for short, was an excellent university professor and internationally renowned scientist who developed and promoted teaching and research in our field in a particularly commendable manner. After completing his civil engineering studies with a specialization in structural engineering at the Technische Hochschule Hannover (TH), he began his professional career in 1965, initially as a software engineer. Later in 1968 he became an assistant to Prof. Dieter Withum at the newly founded Chair of Fluid Mechanics with the Department of Electronic Computing in Civil Engineering. Under the guidance of Prof. Withum and his extensive experience with the Zuse computer Z23, it was a challenging task to develop numerical models for structural engineering and hydro-engineering purposes and also to offer the new programming skills and finite element methods in the teaching of students. Back at that time, a real pioneering period began with the basic development of numerical methods, to which other colleagues from Hannover, such as Prof. Flessner and Prof. Werner, also made significant contributions. By support of the German Research Foundation (DFG) new and essential developments in numerical methods in fluid mechanics took place in the Collaborative Research Center 79 of the Technical University Hannover (TU) "Water Research in Coastal Areas" (1971-1982), which also attracted great international attention. Thus, at the Chair of Fluid Mechanics Dr. Grotkop, for example, developed the world's first FEM North Sea model, and Peter Holz and his team designed a hybrid hydraulic-numerical river model whose hydraulic component was operated in the laboratory of the Franzius-Institute and whose supplementary digital model ran on Peter Holz's process computer, which controlled and regulated this integrated simulation model online via long-distance telephone data transmission - a real sensation. During these eventful time, Peter Holz received his doctorate from the TU Hannover in 1970 and he later qualified at the University by habilitation in the field of mechanics in 1975.

Through innovative research and its presentation at international congresses, he also made contacts and friendships with numerous foreign scientists in Europe, Asia and overseas over the course of his career. This resulted in several longer research stays, for example at the University of Novosibirsk in Akademgorodok (USSR), the University of Waterloo (Canada) and intensive collaborations with Prof. Wang from The University of Mississippi in Oxford (USA) and with Prof. Kawahara from the Chuo University in Tokyo (Japan). The pioneering research successes of Peter Holz in Hannover were primarily supported by the new availability of decentralized computer systems at the Faculty Institutes in the field of Mechanics and by the subsequently following use of personal and workstation computers in the 1980s. The restrictions on the mainframe computers of the university computer centers in punch cards or terminal operation were no longer applicable. Completely new and individual development perspectives for graphical-interactive systems at the workplaces and for the conception of powerful numerical models for structural and hydro-mechanics emerged, combined with various possibilities of a fast-reacting and illustrative verification of the numerical simulations of real phenomena.

In 1980 Peter Holz was appointed as Professor for Electronic Computing in Civil Engineering at the TU Hannover as a colleague of the new Ordinarius for Fluid Mechanics, Prof. Werner Zielke. This resulted in mutual synergies at this Institute which decisively shaped and made known the science of numerical fluid mechanics in the years that followed. These were publicized especially at the 4th International Conference on Finite Elements in Water Resources, which he organized together with his colleagues Zielke and Meissner at the TU Hannover in 1982. Also, the cooperative research, sponsored by the German Research Foundation (DFG), in the field of "Coastal Engineering" (1983-1990) at the University of Hannover achieved a great reputation.

At that time, Peter Holz consistently used the new computer technologies and software methods for the further development of the numerical methods of Informatics in Civil Engineering. Over the course of time, large and powerful models for rivers, tidal estuaries and sea areas were developed together with his assistants, which were able to simulate the flow regime and the transport of pollutants in the complex natural environment on workstation computers with high precision. For these achievements it was necessary, on the one hand, to represent the topography and structure of such areas geometrically precisely with new graphic methods and models and, on the other hand, to simulate the flow dynamics efficiently in adaquate numerical models of the finite element or finite difference methods. Back then, with great commitment, Peter Holz and his co-workers managed to model even highly complex systems realistically, such as the North Sea with its dry falling tidal flats at the German coast, and to simulate the flow processes with the highest quality. Of course, this also included the sufficiently precise representation of the influence by natural forces as well as the boundary and initial conditions from meteorology and hydro-mechanics. All of this was tackled in an admirable way during the 1980s at the Institute for Fluid Mechanics and Electronic Computing in Civil Engineering at the University of Hannover.

In 1984, Peter Holz was a founding member of the German Association of Computing in Civil Engineering, whose professional origins go back to the work of the civil engineer Konrad Zuse as the inventor of the first programmable computer Z3. In cooperation with other university professors in that field, he has made an exemplary contribution to the development and implementation of a joint concept for teaching and research in Informatics in Civil Engineering at German-speaking universities. This also had a decisive influence on the reorganization of the civil engineering faculties at German universities after the German reunification in 1990. With his many years of teaching and research experience, since 1975 as a university member at the universities in Hannover and Cottbus, he has had a lasting influence in the field of civil engineering and its design in a forward-looking way.

In 1993, Peter Holz was appointed as a Professor of Informatics in Civil Engineering at the newly founded Brandenburg University of Technology (BTU) in Cottbus. Accepting this position was a courageous decision with great impact for his future career. His professional life shifted to Cottbus and he moved his residence to Berlin. With the consistent development of the new possibilities of the Internet, the webbased working methods and network-based, multimedia information processing, a new focus of research in Hydro-Informatics and Informatics in Civil Engineering was successfully established. His group also took an active and creative part in various projects of the DFG-Priority-Program "Object-oriented modeling in planning and construction" (1991-1998) and "Network-based cooperative planning processes in structural engineering" (2000-2007), which the German Association for Computing in Civil Engineering led by Prof. Hartmann resp. Prof. Rueppel / Meissner initiated in cooperation with colleagues from Informatics and Structural Engineering. Due to his commitment, he personally contributed to the fact that relevant results of the German research in the field of Informatics in Civil Engineering could be successfully presented at several international congresses and received attention in this specific field.

The scientific cooperation with many colleagues from the international community was very important to Peter Holz and was a core element of his successful work. For instance, with his colleagues Sam Wang from the USA and Mutsuto Kawahara from Japan, he initiated and established the biennial International Conference for Advances in Hydro-Science and Engineering, and in 1998 he also organized this event at the BTU Cottbus. The conference in Cottbus was a great success with many participants from all over the world who discovered Cottbus as a new scientific center for computational engineering in Germany and which made the BTU internationally well-known. Several European research projects with partners from France, Denmark, the Netherlands, Great Britain and Poland established the importance of his chair in Europe and contributed to the fact that his projects at times raised more than half of the third-party funds for the Faculty of Architecture, Civil Engineering and Urban Planning. As a scientist, he has earned high national and international reputations through his numerous research projects and the large number of specific lectures and publications. 

With the recognition of the diverse research, his chair also developed successfully several cooperative teaching concepts with innovative contents at European and international level. With the course HydroWeb – Web-based Collaborative Engineering in HydroSience, offered by the BTU Cottbus since 1999, up to now over 800 students from more than 25 universities have learned how to successfully work on river management projects together in international teams via the Internet. From this international range of courses, Peter Holz and colleagues from five European universities (Nice, Cottbus, Budapest/Warsaw, Barcelona, Newcastle) developed the Erasmus Mundus Joint Degree Master's program EuroAquae – Hydro-Informatics and Water Management, which has been continuously funded by the EU since 2004. This European course, which now has 18 generations of participants and over 500 students/graduates from all over the world, is an example of Peter Holz's extensive scientific achievements in Hydro-Informatics and Informatics in Civil Engineering. Numerous students, co-workers and colleagues contributed to its implementation in teaching and practice and are still going on to continue with his heritage. Peter Holz had the extraordinary ability to bring people together from all over the world and to motivate them for new ideas and methods and their implementation.

Even after his retirement in 2005, he was able to continue contributing his extensive knowledge, his experience, but also his innovative strength to several activities at BTU Cottbus, initially for three years as a guest professor and then later with teaching assignments, guest lectures and as an external expert with advice and by actions. During his long tenure in Hannover and Cottbus, he significantly influenced many colleagues, both nationally and internationally, who are now in leading positions in teaching, research and professional practice.

It is with a heavy heart that we bid farewell and commemorate with great gratitude and high recognition of his important contributions and scientific achievements. Peter Holz, born on May 4, 1940 at Neumuenster, Germany lived to the age of 81. As a passionate sailor, his soul now, after the sea burial in Strande near Kiel, finds its eternal rest in the wideness of the Baltic Sea, which he loved so much as a sailing area!

Udo F. Meissner | Technical University of Darmstadt 

Frank Molkenthin | Brandenburg University of Technology 

Eberhard Pfeiffer | University of the Bundeswehr at Munich