Evaluating a topo-bathymetric lidar sensor to map river channels for improved hydrodynamic flood risk mapping

许多社区都感受到了河水泛滥的影响，最近在阿尔伯塔和大草原，这些事件造成了数百万美元的损失。在新斯科舍省，社区在2012年受到洪水的严重影响。 总部位于哈利法克斯的工程公司CBCL和NSCC的应用地理信息学研究小组（AGRG）提议采用创新的激光雷达技术，以更好地了解河流系统，并通过更明智的缓解策略减少未来洪水事件的影响。分水岭和洪泛区的地形或海拔以及土地利用与河流洪水的原因和地点有很大关系。关于流域的土地利用和地形的信息可以使用各种成熟的技术（航空照片，卫星图像和激光测高-激光雷达）绘制。然而，为了了解河流在溢出到洪泛区之前可以容纳多少水，我们必须知道河底和河岸的海拔。用于预测河流洪水的水力模型需要精确的河流横截面几何形状和洪泛平原高程。目前，缺乏代表这些关键模式投入的适当调查数据。收集这些数据的传统勘测技术，例如涉水过河或执行基于浅水船的回声测深勘测，是昂贵的且潜在危险的。 NSCC的新测绘系统，地形测深激光雷达，利用安装在飞机上的激光精确测量河流周围的地形，也可以透过水来测量下面的东西。该传感器将测量河底地形，底部粗糙度和成分，包括可能导致摩擦和减缓水流的植被。该传感器还能够准确测量人为特征，例如阻碍系统内水流的桥梁。通过将激光雷达传感器安装在飞机上，可以快速测量大面积区域，并提供比传统方法更多的信息。与以前的方法相比，这种新方法有可能提高我们以更低的成本准确绘制河流系统的能力。

The impacts of river flooding have been felt by many communities, most recently in Alberta and the prairies, where these events have caused millions of dollars damage. In Nova Scotia, communities were severely impacted by flooding in 2012. CBCL, a Halifax based engineering company, and NSCC's Applied Geomatics Research Group (AGRG) are proposing to adopt innovative lidar technology to better understand river systems and contributing areas that drain into the river to reduce the impacts of flood events in the future through more informed mitigation strategies. The topography or elevation of the watershed and floodplain and the land use have a lot to do with why and where a river floods. This information on the land use and topography of the watershed can be mapped using a variety of well-established techniques (air photos, satellite imagery, and laser altimetry - lidar). However, in order to understand how much water the river can hold before it spills out onto the flood plain, we must know the elevation of the river bottom and banks. Hydraulic models used to predict river flooding require accurate river cross-section geometry and flood plain elevations. Currently, there is a lack of adequate survey data representing these key model inputs. Traditional survey techniques to collect these data, such as wading across the river or performing shallow water boat based echo sounding surveys are expensive and potentially dangerous. NSCC's new mapping system, topo-bathymetric lidar, utilizes lasers mounted in an aircraft to precisely measure the topography surrounding a river and can also see through the water to measure what is below. The sensor will measure the river bottom topography, bottom roughness, and composition including vegetation which can cause friction and slow the flow of water. The sensor is also capable of accurately measuring anthropogenic features such as bridges which bottleneck the flow of water within the system. With the lidar sensor mounted in an aircraft, large areas can be surveyed quickly and provide more information than traditional methods. This new approach has the potential to improve our ability to map river systems accurately at a cheaper cost when compared to previous methods.