从陆地到水的建模

Author:莫妮卡·米勒·罗杰斯（Monica Miller Rodgers）

气候变化正在影响全球淡水供应的机构。科罗拉多河经过美国的七个州到达墨西哥，在墨西哥倒入科尔特斯海，就是这样的例子。

水流被归类为2015年美国最濒危河流的水。reduce by 10 to 30 per cent到2050年。天气温暖，降雪量较小，河流中内置的数百多个水坝对其生态系统施加了重大压力。这不利地影响了鱼类和野生动植物的栖息地：

• $26 billion recreational economy,
• 4000万人依靠河流每天用水，
• 200万公顷的农田灌溉。

美国填海局（BOR）对科罗​​拉多河的健康有如此多的骑行，负责监督水资源管理和水的水，以便更好地了解盆地地貌学。

“我们正在努力了解科罗拉多河正在发生的事情，”said Carrie Scott, chief of BOR’s Yuma Area Office technical support office.“我们对河流进行建模，以了解整个浅水中的沉积物沉积物，进而帮助我们确定诸如河岸降解或流动中的'choper点'之类的水。”

与任何河流的性质一样，科罗拉多河的蜿蜒曲折是改变其自然路线。这对附近的建筑物构成了威胁，例如道路，农业和住宅社区。博尔（Bor）努力通过挖泥和武装银行线路将河水保持在路线上。

“河的水大师,我们需要存在ure continuous water delivery. We have an ongoing program to contract for a study to map the river by reach to understand how the riverbed is changing,”said Scott.“我们收到的数据有助于我们更好地建模河流的表面和地下。我们拥有的质量越好，我们就越能建模和了解各种水流的影响，并为沿河的项目产生了工程设计。”

Turning to Allied GIS, a mapping firm specialising in GIS, imagery and database applications, the firm was tasked to build a digital orthophotography and a topographical map that met the U.S. national mapping accuracystandard of 30 cm。然后，Allied GIS与德克萨斯大学奥斯汀分校杰克逊地球科学学院（局）的杰克逊地球科学学院合作，以获取机载的浴综合激光雷达数据和另一家调查公司，以提供地形激光雷达和地面支撑。

从测深到地形

A long-time user of Leica Geosystems airborne sensors, researchers at the Bureau used theirLeica Chiroptera空降系统收集加利福尼亚和亚利桑那州下科罗拉多河流域的数据。

Chiroptera有两个独立的激光扫描仪：

1. 近红外(红色光束)地形LiDAR
2. 测深痛的可见（绿波长）

Chiroptera旨在与两个扫描仪同时获取数据，从而在具有浅水体的复杂景观中进行调查。河流调查是在高于地面的400 m，这是最佳海拔for collecting bathymetric LiDAR data. The topographic scanner acquired data simultaneously with a repetition rate of 300 kHz to distinguish the water-surface, and to map the immediate shoreline.

“ chiroptera允许我们捕捉河流的测深方面和近距离地形的特征”said Kutalmis Saylam, the lead research scientist for the Bureau.“We’ve been using our Chiroptera for more than four years now, and we can rely on this robust and intuitive system in the field. That’s very important for us as reliable sensors are a must for our work.”

调查地点的天气状况主要是理想的，总共完成了9个任务。调整了飞行计划，以维护安全飞机操纵，尤其是在调查区的北端，高山峰。整个调查133条飞行线覆盖area of 265 km²完成了21小时的空降时间。

清楚地看到

任务的一部分包括收集来自世界上最深的水坝。亚利桑那州和加利福尼亚州之间的帕克大坝的挡土墙高度为98 m，根据季节的不同，将水排出不同。在与大坝管理局的协调下，该局安排了较低的出院期间的空降任务（146对252 m³/sec) for possible lower turbidity levels in the water-column. Because turbidity absorbs light beams and prevents them from penetrating into deeper water column, it is an essential part of quality assurance procedures for conducting a successful ALB survey. The average reading was 0.41 nephelometric turbidity unit (NTU) in the northern sections of the river, which indicated overall low levels of turbidity in the water-column. In the south, the river was shallower, running through a desert-like environment and losing much of its water to irrigation. These conditions contributed to higher turbidity levels of up to 6.25 NTU and created difficulties for LiDAR beams.

“骨翅目的坚固光束很容易渗透到河北部的晴朗水域。我们创建了一个无缝的水底表示，深度超过10 m，”塞拉姆说。“在浊度较高的南部，我们使用了可用的回报和插值方法来估计和创建水底代表。

Leica LiDAR调查套件LSS v2.3软件包含一种更新的浑浊水算法，该算法过滤了低或中等水平的浊度产生的反向散射噪声，并选择最独特的峰作为水底表示。

“This algorithm enabled the discovery of more returns from deeper waters of the river, and we measured an overall improvement of 81 cm compared to normal returns - a significant achievement in LiDAR bathymetry,”塞拉姆说。

Facilitating the study of the lower Colorado River basin geomorphology and further understanding of the effects of climate change, the Bureau was able to provide an accurate and detailed map.

“我们能够按照美国开垦局要求的河水底部，海岸线和河流整体地形量化水柱的深度”。塞拉姆说。“This valuable knowledge enables us to undertake similar projects in the future, and the reliability of Chiroptera allows us to continue focusing on similar scientific studies.”

BOR will further use the digital orthophotography and the topographical map to match its in-house survey team’s measurements from boat and ground means. The LiDAR study conclusions will continue to help BOR to keep Colorado River flowing in the right direction and supporting those who depend on it.

“The data we received from the LiDAR was calibrated to our in-house team’s surveys,”said Scott.“This information is important to our ongoing operation to continue to improve our models so we can correctly identify what’s changing what could hap-pen and to develop our projects according to conditions.”