GISdevelopment.net ---> AARS ---> ACRS 1992 ---> Poster Session Q The application of the Remote Sensing in river engineering scale modelling Luo Dan,Chen Xuelian The scientific Research Institute Pearl River Water Resources Commission Guangzhou, 510611, China A new verification measure for river engineering scale modeling --- Remote Sensing. Remote Sensing and river engineering scale modeling are two essentially different fields. In river engineering scale modeling, researched are flow structure and bed reformation in rivers under natural conditions or under the effect of engineering structures. This kind of models is built based on the mechanical laws of flow and sediment movement, reproducing the boundary conditions and dynamic conditions similarly to prototype. Experiments are undertaken in a model much smaller than the prototype. While in Remote Sensing, the objectives and phenomena are not touched, optical or eletro-optical instruments on a plane, a shuttle or a satellite receive the electro-magnetic wave signals reflected or radiated by ground objectives several kilometers, several hundred kilometers or even a thousand kilometers a way. The signals are recorded on films or tapes and transmitted back to ground stations. Through information processing, identification analysis and field test, these signals can finally serve for resources exploration, dynamic monitoring of projects and planning decision making of authorities. In a word, if Remote Sensing reproduces the temporal dynamic macro-information of ground features, then great effort is paid on the similarity of a river engineering scale model to the natural condition of the objectives. Scale modeling is based on the similarity theory. The modeling result can be used to forecast what will happen in prototype only when the similarity criterions set in the theory are satisfied, ie. the model is seriously similar to prototype geometrically, kinetically and dynamically. However, it is very difficult. Therefore, after it has been built, a model must be verified for its similarity in the three aspects, ie. similarities of geometry (including elevation and horizontal position), of surface flow pattern, hydraulic grade line and velocity distribution with various discharges and tidal conditions. Formal experiments can be done only when all the factors are similar to prototype. Ti can be seen that similarity verification is an extremely important procedure in scale modeling, and its accuracy is directly involved in whether the result of the scale modeling is correct or not. The classical method of verification is to describe the corresponding physical quantities in the model and in prototype with the same physical formula, which is quite a compilated process. As satellite Remote Sensing data can cover a broad observation area and give out the true condition of ground features, it may be considered as a measure for the similarity verification of river engineering scale models, which is different form classical ones. It gives us essentially a full face pattern rather than quantities. This kind of similarity verification can very visually reproduce flow conditions, tendencies of sediment movement and the boundary conditions in prototype in nature, although it can not describe the kinetic quantities by numerical data. If used is multi-time-phase and multi-wave-band satellite Remote Sensing information, the flow condition changes can be observed of different seasons and under different tidal conditions. Therefore, it is feasible to take satellite Remote Sensing for and assistant measure of similarity verification in river engineering scale modeling. Application of Remote Sensing in the scale modeling of the projects in the sea area in the vicinity of Macao. The authority of Macao has decided to built an international airport, a deep harbour and the second trans-sea bridge in the sea area in the vicinity of Macao. “The scale modeling of The Projects In The Sea Area In The Vicinity of Macao” was conducted by our institute, trusted by Marine Department of Macao in Feb. 1990. The purposes of the experiment are to research the change of the tidal level, velocity, flow dierdtion, sediment movement tendency and deposition location occurring after the projects are completed, so as to evaluable the plan of the projects. After the model was completed, verified by classification means was the similarity of tidal level, flow velocity, flow direction and tidal volume. Further more, satellite Remote Sensing information under the same tidal conditions as in the modeling is chosen to verified area and flow pattern in the simulated area for its large observation area and its ability of reflecting dynamic changes. The three islands of Macao are situated at the mouth of Lingdingyang Bay in Pearl River Estuary. On its east side is the west shoal in Lingdingyang; on its west side is Hongwan Channel, one of the three sea-going channels of Modaomen Outlet; on the south side is the outer sea area of Pearl River Estuary. Situated at such a special position, its sea area must be affected by ocean dynamics and river dynamics at the same time, and the characteristics of flow and sediment movement must also be affected by many dynamic factors. In order to verify the flow pattern in the nearby water area, i.e. in the area of the east inlet of Hingwan Channel and Coloane Island, lighten floats were dropped in under the trans-sea bridge in the model, then photos of the flow patterns in flood tide and ebb tide periods were obtained by track-photography. Fig. 1 is a photo of flow pattern in ebb tide periods in the model, well consistent with the flow pattern shown on the satellite image taken in the ebb tide period on July 30. 1986 (Fig. 2), when the runoff from Modaomen gave a large effect on this sea area. Fig. was taken in a flood season when the sediment concentration of water is large in The West River and small in the flow coming from Lingdingyang Bay. There is a sharp interline between the two streams of flow, one of which is clear and the other is muddy. Particularly, the flow track of the muddy water from Hongwan channel is very similarly to that in the model. Since satellite images is a true reflection of ground information, the fact that the flow pattern in the model is similar to prototype. This is a verification of the flow pattern similarity in river engineering scale modeling. In the scale modeling of the projects in the sea area in the vicinity of Macao, Remote Sensing, as a new verification measure in addition to the classical verification method, offered a strong testimony for the exactitude of the test result. The result has aroused the truster’s great interest and won their appreciation. It is the first experience in both fields of river engineering scale modeling and Remote Sensing to use satellite Remote Sensing information in verifying the flow pattern similarity of river engineering scale models so as to provide scientific basis for feasibility checking of projects in sea. It not only provides a new verification measure for scale modeling, but more importantly also shows a new way for Remote Sensing technology to combine with practical production and to serve for construction. It is proved by practice that so long as it is applied on practical production, Remote Sensing will be brought into full play and have infinite life force. Fig. 1. Photo of flow Pattern in ebb tide period in the model Fig. 2. The TM satellite image taken in the ebb tide period on ground