logical construction and algorithm implementation ... · “naturalistic” waterscapes is intended...

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Journal of Digital Landscape Architecture, 3-2018, pp. 107-118. © Wichmann Verlag, VDE VERLAG GMBH · Berlin · Offenbach. ISBN 978-3-87907-642-0, ISSN 2367-4253, e-ISSN 2511-624X, doi:10.14627/537642012. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by-nd/4.0/).

Logical Construction and Algorithm Implementation: Research on Parametric Designs of Naturalistic Waterscapes

Yuan Yangyang1, Chen Yulong2, Cheng Yuning3 1Southeast University, Nanjing/PRC 2Southeast University, Nanjing/PRC 3Southeast University, Nanjing/PRC · [email protected]

Abstract: The design of “Naturalistic” waterscapes is intended to not only have natural interest, but also become self-sustaining by simulating the form of natural waterscapes, by starting from interpreting generation rule of their natural counterparts. This paper applies the parametric method to the design of “Naturalistic” waterscapes, compiles an algorithm by applying Grasshopper and Rhino software and based on the design logic construction, creates a parametric design model for “Naturalistic” water-scapes. Following this, the paper discusses the parametric design process of Naturalistic waterscapes in combination with the design practice of the Meirenchong Scenic Area in China’s Nanjing Flower Park.

Keywords: Landscape design, naturalistic waterscape, parametric design, design logic, algorithm compilation

1 Introduction

Waterscape design is an important element of landscape design. Natural waterscapes have irregular and free forms, a complete aquatic ecosystem, and are an integral part of the natu-rally networked system of natural water resources (CHENG 2010). “Naturalistic” indicates the creation of a landscape environment like nature, but through artificial means. The design of “Naturalistic” waterscapes is intended to create a waterscape which not only has natural in-terest, but can be self-sustaining through the simulation of natural waterscape forms, done by starting from a systematic perspective and based on interpreting the generation rule of natural waterscape (YUAN 2016).

Naturalistic waterscape design emphasizes the minimization of localized disturbances, and requires the selection of an area with the potential for a water catchment for storage. Storage can be accomplished by means of reasonable damming, done in the design of a form of a natural water body, based on hydrological analysis. Therefore, there are three key points in the creation of a Naturalistic waterscape: water quantity, dam height and water body shape. According to the generation rule of natural waterscapes, there is a dynamic connection be-tween water quantity, dam height and water body shape. The design of Naturalistic water-scapes is a systematic project, and requires dynamic balance and the comprehensive adjust-ment of multiple design factors (CHENG 2015). Traditional design methods mostly depended on landscape designers’ experience, and have relatively strong subjectivity, fuzziness and probability; while parametric design methods are more rational, objective and precise using the application of computer technology. By applying parametric design methodology to the design of Naturalistic waterscapes, we may construct a parametric model by starting from the generation rule of natural waterscapes, and taking the “shape-dam height-water quantity” parametric design logic of Naturalistic waterscape as the core, it is possible to withdraw key

108 Journal of Digital Landscape Architecture · 3-2018

design parameters, generate design results by adjusting and controlling parameters, realize real-time feedback, and obtain the best design scheme for Naturalistic waterscapes through adjustment and optimization. This paper applies Grasshopper software (GH) to compile al-gorithms in Python language, realizes the coordinated design of multiple design elements, and presents the parametric Naturalistic landscape design results with Rhino software.

2 Construction of Design Logic

2.1 Interpretation on the Generation Rule of Natural Waterscape

Natural precipitation converges in depressions on the ground and forms water surfaces. Water sources and depressions are the two key factors for the generation of a water body. The pre-cipitation reaching the ground mainly consists of four parts: The first part is intercepted by vegetation surfaces, in a process called as interception; the second part is directly absorbed by soil, through a process called osmosis; the third part is stored in some small craters and depressions on the ground surface, in a process known as water storage in depressions; and remaining rainwater flows along the surface of the ground, thereby generating surface runoff, and finally converging into water bodies such as channels, rivers, and ponds, among others (MARSH 2010). Natural precipitation is the main water source for a Naturalistic waterscape, and the water quantity of a waterscape is jointly determined by the area of the water catch-ment area, the precipitation quantity of the unit area, and the interception quantity of the ground surface. Depressions are generated through many means, and they are defined as low-lying areas which may be formed on a ground surface by means of artificial damming or excavation (Figure 1). In order to minimize disturbances to the natural environment and re-duce engineering workload, depressions are generally created by selecting an area in a suita-ble landform, which is done in combination with hydrological analysis by means of reason-able damming and local landform pectination. In addition, the shape of a waterscape is also a key point in the design of a Naturalistic waterscape. The two-dimensional shape of a wa-terscape is merely the shape of the water surface, and is the horizontal section of a water body and a landform. The shape of a water surface is jointly affected by landforms and water quantity. Due to the ups and downs and changes in natural landforms, different water levels will cause different water surface shapes. It may be understood from the generation rule of natural water bodies that there is a dynamic connection between water quantity, water body shape and dam height; this is also the generation foundation of the parametric design logic of Naturalistic waterscapes.

Fig. 1: Schematic diagram of the “depression” formation

Y. Yangyang et al.: Logical Construction and Algorithm Implementation 109

Water bodies do not exist independently under natural conditions. In accordance with the grading of runoff, surplus water quantity of the last level will converge up to the next level, and water bodies of different elevations are connected in series through rivers and form a water network systems. Water catchment areas present a nested hierarchy according to the grading of runoff, and the quantity of water catchment in high-level water catchment areas is the sum of the quantity of water catchment from the last level. For water network systems, a waterscape in the water catchment area of a level is the difference between the water quantity intercepted by the waterscape at the last level and the quantity of water catchment (SHREVE 1966) (Figure 2).

Fig. 2: Composition of a Water Catchment Area

2.2 Construction of Naturalistic Waterscape’s Parametric Design Logic

The parametric design logic of Naturalistic waterscapes corresponds to the generation rule of natural waterscapes, and is comprised of five submodules, which are 1) the dam data pro-cessing module, 2) the landform data processing module, 3) the water body generation and water quantity calculation module, 4) the earthwork data calculation module and finally, 5) the water body shape evaluation module. The functions of these submodules are to: determine a dam site, optimize landforms, generate water bodies, calculate water quantity and earth-work volume, and optimize water body shape respectively (as shown in Figure 3). As such, the first two modules are used to process basic data inputs from the outside, and convert the data into the types available for use inside Grasshopper; while the latter three modules are used for the calculation and visualized expression of the data obtained, and to facilitate the evaluation of water body shapes and the man-machine interactive optimum design. The water quantity calculation module is the direct expression of the “shape-dam height-water quantity” design logic, and also the core of Naturalistic waterscape design logic.

There are two foundations of early-stage research for the construction of the parametric de-sign logic for Naturalistic waterscapes: The site selection of the waterscape and the estab-lishment of a water body shape database. For the site selection of a waterscape, this paper uses ArcGIS software to construct a parametric site selection process, which carries out hy-drological analysis through scenery of the environment, while also screening for areas with potential as a water catchment to serve as a site for waterscape design. The software also designs water network levels, namely the quantity and position of water surfaces, done in accordance with landforms and runoff at the site, as well as the conditions of the water catch-


ment area itself. The water body shape database includes water body shape data of popular and widely appreciated lake waterscapes in dozens of scenic environments (Figure 4), com-plete with concrete indexes including area, longest axis, aspect ratio, shape ratio, compact-ness, shoreline development coefficient, and others. In the parametric design logic of Natu-ralistic waterscapes, the “water body shape evaluation module” is related to the database, and the range values of relevant indexes are taken as the basis for evaluation of water body shape.

Fig. 3: Logic for Naturalistic Waterscapes’ Parametric Design


Fig. 4: Water Body Shape Construction Database for Lake Waterscapes

Additionally, the parametric design logic of Naturalistic waterscapes is constructed with a single water body in mind. For a water network system consisting of multiple water bodies, based on the construction of the parametric design model according to the design logic, we shall connect the parametric design model of each independent water body according to the water quantity relationship of the water body at each level in the same water catchment area, and thus generate a parametric design model of the whole water network system.

3 Rules for Compilation of the Algorithm

The parametric design model of Naturalistic waterscapes screens parameters based on the early-stage analysis and evaluation data including waterscape site selection, quantity of water catchment, site topography, water body shape evaluation, and others (Table 1). Concurrently, inputs of early-stage research data act as initial constants in the model. This paper executes algorithm compilation and model construction for the five sub-modules of the logic for Nat-uralistic waterscape parametric design with Python language, and based on the Grasshopper software platform. Thus, we compiled the “dam height-water quantity” algorithm, the “water body-landform” algorithm, the “water quantity-earthwork volume” algorithm, and the water body shape algorithm (Figure 5) by selecting reasonable calculation methods according to the parametric design logic of Naturalistic waterscape and the actual situations of the water-scapes’ design. The height of a dam is determined based on the water catchment quantity data obtained from the site selection and the calculations for a water body, in combination with the landform data demand. However, we found the “volume-height” algorithm to be over complicated with too many restricting conditions, and it cannot be covered with a single algorithm. Therefore, when focusing on the “dam height-water quantity” relationship, a solid difference set in Grasshopper is adopted to compare the water quantity needed for any water body and the site water watchmen quantity, which adjusts the input dam height data, keeps the water quantity needed for a water body and the site water watchmen quantity within the error scope, and thus a determination can be made regarding data for dam height.


The concrete algorithm rule is as follows: cut off the landform curve from the present water body cube and obtain the water body (solid) for the calculation of volume and the withdrawal of a contour line. Following this, obtain the damming site (point set) according to the results of site selection for a water body, and draw the dam datum line in combination with is height. By taking this as a base point, expand the datum line in the landform direction, thus obtaining the water datum surface. When this is complete, zoom in on the datum surface with datum line as the centre to guarantee tallying with a landform while obtaining the water calculation surface. Then, based on relevant landform data (curve surface) obtained in the early-stage calculation module, input the parameters for dam height (absolute height), and extend the water calculation surface upward to obtain the water calculation body needed (Figure 6).

Table 1: Parameters for Naturalistic Waterscape Parametric Design

Name Meaning Data type Control method Symbol

Site topogra-phy

Express the landform trend of the site

Curved surface

Manual control Sa

Dam height The altitude of any dam body Number of floating points

Manual control Hd

Dam shape The intrinsic shape of any dam body, including position infor-mation

Curve Manual control Cd

Water body The water body enclosed by any dam

Physical object

Automatic gener-ation

Bw

Water body contour line

The planar contour line formed by any water body

Curve Automatic gener-ation

Cw

Water quantity

The volume of water body Number of floating points


Vw

Dam slope The slope stacked by earth-works constructing a dam’s body

Number of floating points

Manual control Sd

Dam body The earthwork construction of any dam

Physical object


Bd

Earthwork volume

The volume of earthworks needed for the construction of any dam

Number of floating points


Vd


Fig. 5: “Dam Height-Water Quantity” algorithm, “Water Body-Landform” algorithm,

“Water Quantity-Earthwork Volume” algorithm, Water Body Shape algorithm

Fig. 6: Rule for the “Dam Height-Water Quantity” algorithm


This paper builds the parametric design model of a water system based on constructing a parametric design model for a single water body and by relating multiple water bodies in the same water catchment area through water quantity. In the algorithm’s compilation, it is nec-essary to realize the synchronous treatment of multiple single water bodies through the tree-shaped data structure in Grasshopper software, namely adjusting the data of a single water body into a tree-shaped data structure, and generating the data of multiple water bodies through the adjustment of water quantity. By using Rhino software, it is possible to present results of a Naturalistic waterscape design in real-time generated by parametric regulation and control. Water quantity, dam height and water body shape jointly form a set of parameter modification schemes, which is fed back to the dam data module and landform processing module, and after adjustment and optimization for multiple rounds, the design results will be outputted.

4 Case Study

Nanjing Flower Park is located in the north part of Nanjing’s main urban area, in Jiangsu Province. It covers a total area of 78.3 ha. The site is of a typical hilly physiognomy, with low mountains and hillocks, and is higher in the northeast and lower in the southwest on the whole. In the east of the site is the natural mountain body Nongchang Mountain, which has a maximum altitude of 123.00 meters and a minimum altitude of 22.50 meters, with a maxi-mum height difference of 100.50 meters. This site was originally a nursery, and in 2016, the Nanjing Municipal Government planned to turn it into a flower-themed park. Inside the site of the Flower Park, there are multiple and dispersed small water surfaces, which do not form a relatively good water network system. The planning and design of Flower Park aims to sufficiently connect the existing water bodies at the site and optimize the water system’s shape, thus generating a sustainable water environment while building diversified water-scapes. At the same time, a good micro-climatic environment for the growth of plants will be provided. This paper selects the Meirenchong Scenic Spot in Flower Park to discuss the par-ametric design process of Naturalistic waterscapes (Figure 7).

Fig. 7: Location of Nanjing Flower Park and digital elevation model of its current landform

Before the parametric design of a Naturalistic waterscape, it is necessary to analyse and re-search the hydrological situation of the site, and partial data therein will be used as the basic numerical values for the parametric design. First, the design employs ArcGIS software in


order to carry out hydrological analysis on the site, including the runoff and water catchment area, among others (Figure 8). According to results of analysis on the runoff at the Meiren-chong Scenic Spot, and in combination with the landform, this paper screens the sites with potential for the creation of waterscapes, and determines the single water bodies in the water system and their corresponding damming positions. Second, according to the annual precip-itation of Nanjing, this paper calculates the annual quantity of water catchment in the water catchment area: 16,828 m3. This is merely the total water quantity of the designed water system.

Fig. 8: Hydrological Analysis of Nanjing Flower Park

Based on early-stage analysis, this paper constructs a model for the parametric design of the Naturalistic waterscape in Meirenchong Scenic Spot using the Grasshopper software plat-form. First, according to the result of water body site selection, this paper creates a design for a single water body. After the parameter value for dam height is inputted into the model, a preliminary water body design scheme may be generated from the “dam height-water quan-tity” module. By applying Rhino software, the body results generated from this calculation may be presented in real-time. For different dam height values, the water quantity, earthwork volume and water body shape of the water body design schemes generated are also different. As shown in Figure 9, if the elevation of the dam is 21.3 meters, the water quantity in the


water body will be 396.8 m3, the slope of dam body will be 0.248, and the volume of earth-works needed for damming will be 3.5 m3. However, if the elevation of dam height is in-creased to 24.5 meters, the water quantity in the water body will be increased to 1,911.6 m3, the slope of dam body will be 0.224 (not a significant change), though the earthwork volume will be increased to 28.4 m3. Due to changes of inundation positions corresponding to dam height, the water body shape also changes. Based on the water body shape database, the water body shape evaluation module could restrict the water body shape generated.

Fig. 9: Changes in Water Body Shape corresponding to Changes in Dam Height Value

After the generation of a preliminary water body design scheme, this paper evaluates water body shape using the water body shape evaluation model, and restricts the water body shape of the preliminary water body design scheme with values from multiple shape indexes in-cluding the longest axis, aspect ratio, shape ratio, compactness, shoreline development coef-ficient, and others from the water body shape database. If the water body shape indexes do not meet requirements, adjustments of the landform control point in Rhino software through man-machine interactive operations are available. Concurrently, the water body shape eval-uation model is able to conduct real-time evaluation and feedback on water body shape after optimization. Through the adjustment of the dam height value and the control of landforms, and by utilizing the parametric design model, generation of multiple schemes for design of Naturalistic waterscape are available. Furthermore, by using water body shape evaluation, obtaining an optimized design scheme for this waterscape is also possible. In addition, based on the tree-shaped data structure model of water systems, single water bodies in the water network system will interact, and the sum of their water quantity is the total water quantity of the designed water system. Through the total water quantity, realization of an optimized design for a Naturalistic water system is achievable (Figure 10).


Fig. 10: Practical creation of Naturalistic waterscape in China Nanjing Flowers Park – Design rendering

5 Conclusion

Grasshopper software is a plug-in program developed based on the Rhino platform, and fea-tures visualization and a high enclosure degree. The application of Grasshopper software has realized high-efficiency and precise design of Naturalistic waterscapes through the construc-tion of design logic, the compilation of algorithms, and the adjustment and control of param-eters. Compared with traditional waterscape design methods, the parametric design model for Naturalistic waterscapes can make possible real-time presentation and feedback for de-sign scheme data, connecting such data with the databases water body shape, and other in-formation. This can help to find the comprehensively optimum option from a multitude of design schemes.

The design of waterscape is a systematic project, which involves not only the design of “shape”, but also the problem of “ecology”. With water quantity as the core of naturalistic waterscape design logic, the research of this paper evaluates the shape of water bodies by introducing the indexes like area, longest axis, aspect ratio, shape ratio, compactness, shore-line development coefficient, and fractal dimension, etc. The above-mentioned water body shape indexes are commonly used in research to discuss the ecological situations of water bodies like lakes (PAN et al. 2003, YE 1988, GAO et al. 2013). The research of this paper constructs a database including the shape of dozens of water bodies of lakes based on water ecological indexes, and uses the database to evaluate the results of parametric design, in order to ensure that the waterscapes generated by means of parameterization have both beautiful shape and healthy ecology. In future, the factors affecting the ecological functions of water bodies, like the buffer zone of water body shoreline and the depth of water bodies, etc. may be taken into the research scope, and corresponding indexes may be constructed and used as parameters to further optimize the parametric design model of naturalistic waterscapes.


Acknowledgment

This paper is funded by the National Natural Science Foundation of China, the project name: Research on Parametric Design of Water Environment in Landscape Architecture (51608108).

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Based on Coupling Theory. Unpublished PhD dissertation, Southeast University.

logical construction and algorithm implementation ... · “naturalistic” waterscapes is intended...

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