1- Introduction

2- Methodology

3- Results

4- Discussion

5- Conclusions

References

Abstract

Uncertainty in capturing the effects of riparian tree shade for assessment of algal growth rates and water temperature hinders the predictive capability of models applied for river basin management. Using photogrammetry-derived tree canopy data, we quantified hourly shade along the River Thames (UK) and used it to estimate the reduction in the amount of direct radiation reaching the water surface. In addition we tested the suitability of freely-available LIDAR data to map ground elevation. Following removal of buildings and objects other than trees from the LIDAR dataset, results revealed considerable differences between photogrammetry- and LIDAR-derived methods in variables including mean canopy height (10.5 m and 4.0 m respectively), percentage occupancy of riparian zones by trees (45% and 16% respectively) and mid-summer fractional penetration of direct radiation (65% and 76% respectively). The generated data on daily direct radiation for 2010 were used as input to a river network water quality model (QUESTOR). Impacts of tree shading were assessed in terms of upper quartile levels, revealing substantial differences in indicators such as biochemical oxygen demand (BOD) (1.58–2.19 mg L−1 respectively) and water temperature (20.1 and 21.2 °C respectively) between ‘shaded’ and ‘non-shaded’ radiation inputs. Whilst the differences in canopy height and extent derived by the two methods are appreciable they only make small differences to water quality in the Thames. However such differences may prove more critical in smaller rivers. We highlight the importance of accurate estimation of shading in water quality modelling and recommend use of high resolution remotely sensed spatial data to characterise riparian canopies. Our paper illustrates how it is now possible to make better reach scale estimates of shade and make aggregations of these for use at river basin scale. This will allow provision of more effective guidance for riparian management programmes than currently possible. This is important to support adaptation to future warming and maintenance of water quality standards.

Introduction

The influence that riparian vegetation exerts on river water temperatures and light availability by intercepting incoming solar radiation has long been studied (Davies-Colley and Rutherford, 2005; Greenberg et al., 2012; Moore et al., 2005; Webb et al., 2008). Shading is a key parameter due to the control it exerts over the amount of direct radiation reaching the river surface making it an important consideration in water quality modelling and management. Solar radiation has direct effects on rates of primary production of both macrophytes and algae (Bowes et al., 2016, 2012b; Wood et al., 2012) which is important for river metabolic regime and is known to be influenced by riparian shade (Bernhardt et al., 2017). Water temperature also directly influences river fauna and dissolved oxygen concentrations. Therefore considerations of shading are of growing importance given the increasing stress on the water environment likely to arise under future climate. Effective and realistic riparian planting schemes to mitigate against these unwanted effects will become increasingly valuable and enhance water ecosystem services (Martin-Ortega et al., 2015). They will provide alternatives to traditional end-of-pipe solutions arising primarily from the EU Urban Wastewater Treatment Directive, which have been assessed through modelling (e.g. at large basin scale across Europe: Grizzetti et al., 2011).

Architectural and urban planning works influence both formation and transformation of historic character of a city, which can be accepted as an evidence of the past society that gives the guidelines for the future development and prosperity. Revitalization and conservation of historic urban areas include aspects of maintenance and renewal of their physical traditional texture together with economic and social dynamism on their development. Hence, the multi-layered structure of a historic city center is necessary to be understood in unity despite of its complex character, which should be defined in a systematic way of geographical information management. Historic urban areas are vulnerable to number of stressors such as rapid urbanization, population growth and natural disasters. Management strategies related to historic urban areas aim to provide the use of cultural heritage for sustainable development of cultural landscapes and natural environment. As Agapiou et al. (2015) mention, conservation of cultural heritage areas require innovative and cost effective tools for systematic monitoring which require costly and time consuming data and information collection procedures for large areas. The importance of digital photogrammetry and laser scanning during process of a digital documentation for an immovable is also reminded by Yastıklı (2007), while geographical information systems (GIS)-based surface analysis is capable to be done systematically on investigating former status of various sites, from archaeological and natural sites to historic mining areas, as studied by Kovács et al. (2011) and Al-kheder et al. (2008). In addition to analyzing the morphological development of a historic city, heritage conservation process is also essential to be assessed and elaborated by digitizing collected input data in different methods. There are several tools, one of which is known as GIS, which is used to manage large data sets for developing sustainable management plans of historic urban areas. The process of urban conservation can be facilitated by making use of spatial database in this system, as already been defined by the scholars (Bilgin Altınöz, 2002; Günay, 2009; Lerotic, 2011). Moreover, He et al. (2015) state that the use of GIS systems brings their own challenges for supporting decision-making strategies because of the large scales of their database system despite of the remarkable advances in its field to support management of cultural heritage sites. As one of the historic cities in Turkey, Bursa, a Nomination File of Bursa as UNESCO World Heritage Site (WHS) since 2014, has followed legal and organizational aspects in conservation issue, which also being witnessed to practices occurred in conservation of historic urban areas since the end of the nineteenth century. It is significant as being the first capital of Ottoman Empire and a developing industrial city in Turkey. Various types of cultural properties have been subjected to different conservation activities, from the public participated symposiums to the restoration applications. These activities have continuously effected to the sustainability of both tangible and intangible cultural heritage in Bursa, which should be studied by searching on historical documents describing faults and successes on the applied projects.